insects

Article

Defoliation of Soybean Expressing Cry1Ac byLepidopteran Pests

Mariacutea G Muruacutea 1 ID Martiacuten A Vera 2 Mariacutea I Herrero 1 Sofia V Fogliata 1

and Andrew Michel 3

1 Instituto de Tecnologiacutea Agroindustrial del Noroeste Argentino (ITANOA) Estacioacuten ExperimentalAgroindustrial Obispo Colombres (EEAOC) Consejo Nacional de Investigaciones Cientiacuteficas yTeacutecnicas (CONICET) Av William Cross 3150 Las Talitas T4104AUD Tucumaacuten Argentinamaria_inesherrerohotmailcom (MIH) sofiavfogliatagmailcom (SVF)

2 EEAOC Las Talitas 4001 Tucumaacuten Argentina alejandrovera_afsyahoocomar3 Department of Entomology Ohio Agricultural Research and Development Center The Ohio State University

Wooster OH 44691 USA michel70osuedu Correspondence gmuruaeeaocorgar Tel +54-(381)-521000

Received 23 May 2018 Accepted 27 June 2018 Published 1 August 2018

Abstract Lepidoptera stink bugs and weevils are important pests in soybean For lepidopterancontrol insecticides and seed treatments are used As an alternative Bt soybean was developedto control primary pests of Lepidoptera such as Rachiplusia nu (Gueneacutee) (Noctuidae) Chrysodeixisincludens (Walker) (Noctuidae) Anticarsia gemmatalis Huumlbner (Erebidae) Helicoverpa gelotopoeon (Dyar)(Noctuidae) and Crocidosema aporema (Walsingham) (Tortricidae) However the use of transgenicplants and the resulting reduction of insecticide against target pests may allow other pest species tobecome more prevalent in agricultural environments Soybean expressing Cry1Ac against differentlepidopteran nontarget and target insect pests was evaluated and its performance was comparedwith non-Bt soybean with seed treatment The treatments were Bt soybean non-Bt soybean withseed treatment (Fortenzareg diamide insecticide Syngenta Buenos Aires Argentina) and non-Btsoybean without seed treatment Larvae of H gelotopoeon Spodoptera albula (Walker) (Noctuidae)Spodoptera cosmiodes (Walker) (Noctuidae) Spodoptera eridania (Stoll) (Noctuidae) and Spodopterafrugiperda (J E Smith) (Lep Noctuidae) were used The plants of each treatment were infested withlarvae of each species and the percentage of leaf damage produced by each species was recordedThe results showed that Bt soybean provided control of H gelotopoeon and had a suppressive effecton S frugiperda and S albula However S eridania and S cosmiodes were not susceptible to theCry1Ac protein in MON 87701 times MON 89788 soybean when evaluated by greenhouse infestationConsidering the performance of each species using non-Bt soybean without seed treatment S eridaniawould represent a potential risk in soybean crops

Keywords Helicoverpa genus Spodoptera complex nontarget and target pests of Bt soybean seedtreatment leaf damage percentage

1 Introduction

Soybean (Glycine max (L) Merrill) is an oilseed plant of the family Fabaceae that is widelyplanted in various countries worldwide [1] Argentina is the third-major soybean producer in theworld covering an area of 192 million hectares [23] Lepidoptera stink bugs (Hem Pentatomidae)and weevils (Col Curculionidae) are important pests that inflict the major yield loss of thiscrop [14ndash8] For Lepidoptera in soybean insecticides and seed treatments are used but Bacillusthuringiensis (Berliner 1915) soybean (Bt soybean) is a new alternative method to control several

Insects 2018 9 93 doi103390insects9030093 wwwmdpicomjournalinsects

Insects 2018 9 93 2 of 13

species [5ndash7910] Bt soybean is a stacked varietal line developed by Monsanto that combinesthe transformation events MON 87701 (expressing Cry1Ac protein) and MON 89788 (glyphosatetolerance) [11] At present Bt soybean provides control for the primary Lepidopteran pests of soybeansuch as Rachiplusia nu (Gueneacutee) (Lep Noctuidae) Chrysodeixis includens (Walker) (Lep Noctuidae)Anticarsia gemmatalis Huumlbner (Lep Erebidae) Helicoverpa gelotopoeon (Dyar) (Lep Noctuidae)Crocidosema aporema (Walsingham) (Lep Tortricidae) Colias lesbia (F) (Lep Pieridae) Spilosomavirginica (F) (Lep Arctiidae) Chloridea virescens (F) (Lep Noctuidae) and Achyra bifidalis (F) (LepCrambidae) This technology can also suppress populations of Spodoptera frugiperda (J E Smith) (LepNoctuidae) Elasmopalpus lignosellus (Zeller) (Lep Noctuidae) and Helicoverpa zea (Boddie) (LepNoctuidae) [11] However the use of Bt plants and the resulting reduction of insecticide use againsttarget pests may allow other pest species to become more relevant in agricultural environments [9]Field trials conducted in northern China showed that mirid bugs (Het Miridae) have progressivelyincreased population sizes and acquired pest status in cotton and multiple other crops in associationwith a regional increase in Bt cotton adoption Bt cotton has become a source of mirid bugs and theirpopulation increases are related to drops in insecticide use in this crop [12] On the other hand theemergence of Striacosta albicosta (Smith) (Lep Noctuidae) as a potential pest of corn in South Dakota(USA) may be related to the widespread planting of Cry1Ab Bt corn hybrids Continuous planting ofCry1Ab Bt corn hybrids over large areas favors this species by effectively eliminating competition fromOstrinia nubilalis (Huumlbner) (Lep Crambidae) [13] Therefore research on the interaction of nontargetpest species with this Bt technology is of great theoretical and practical importance

In recent years the occurrence of caterpillars from the Spodoptera genus (Lep Noctuidae) hasincreased and caused damage to soybean crops in Brazil [14ndash18] and Argentina [5ndash719] Withinthis complex S cosmiodes (Walker) S eridania (Stoll) and S frugiperda are prominent in causingdamage [71620] It is important to highlight that the damage produced by S frugiperda in soybeancrops is common in farms with grasses and pasture weeds before soybean sowing Some of thesegrasses and various pasture weeds [Conyza bonariensis (L) Cronquist (Asteraceae) Brassica campestris(L) Metzg (Brassicaceae) and Sphaeralcea bonariensis (Cav) Griseb (Malvaceae)] play an importantrole as reservoirs for insect pests which move from one to another species of grasses or crops [2122]The presence of S albula (Walker) in soybean crops is occasional and they were also detected in farmswith grasses and pasture weeds

The bioecological characteristics of the Spodoptera complex (polyphagia great voracity in feedinghigh reproductive capacity migration behavior host races) [23ndash31] added to some precedents ofinsecticide resistance and the natural tolerance of Spodoptera spp to the Cry1A protein [3233] making itnecessary to evaluate their behavior with Bt soybean Previous studies that evaluated the susceptibilityand tolerance of different pests suggested that the most susceptible species to the Cry1Ac protein are Agemmatalis R nu and C includens and the most tolerant species are S frugiperda and S cosmioides [3435]While S frugiperda has developed resistance to Cry1F proteins [36ndash38] S eridania and S albula are tolerantto several chemical insecticides [39ndash44] and to the B thuringiensis Cry1Ac gene [4546]

Given the agronomic challenges of soybean production combined with the emerging Spodopterapest complex evaluations of additional control strategies are needed Although various aspects ofSpodoptera spp performance have been studied using different crops or artificial diet through fieldand laboratory studies (Table 1) many of the field studies used natural infestations where the specificidentity of each species was not considered This is due to the fact that the first larval instars of thisgenus in general present similar characters which make it impossible to identify [46ndash49] This has ledto much speculation about the damage of this complex in the field The knowledge about the defoliationproduced by each species will help to determine the real individual defoliation in soybean plants

Insects 2018 9 93 3 of 13

Table 1 Summary of previous studies of the Spodoptera complex and Helicoverpa gelotopoeon (Lep Noctuidae) where the performance of each species was evaluatedusing different crops andor artificial diet in field and laboratory studies

Study Species Identity ofSpecies

EnvironmentalConditions

(Controlled or FieldConditions)

Type ofInfestation Crop or Artificial Diet Used Evaluations Impacts

Present study Sf Se Sa Sc Hg individual controlled(greenhouse) artificial soybean (Bt and non-Bt) Performance and potencial risk

Bt soybean had the best control of Hg and asuppressive effect on Sf and Sa Se and Sc were

not susceptible to the Bt soybean Se represents apotential risk in soybean crops

[60] Sc Se Sf individual controlled artificial soybean (Bt and non-Bt) and diet Susceptibility to Cry1Ac protein Bt soybean showed poor control of Sc Se Sf

[16] Sf Se Sc individual controlled artificial soybean genotypes Larva consumption foliage Sc defoliated nearly twice the leaf area of Sa and Sf

[5] S spp general field conditions natural soybeanDifferent chemical alternatives forthe management of the complex

pestDiamide + neonicotinoid had the best control

[6] Sc individual field conditions natural soybean Moment of application of differentinsecticides

Early application of diamide delayed the damageof larvae

[7] H spp S spp general field conditions natural soybean (Bt and non-Bt) Pest management Early application of diamide delayed the damageof larvae

[8] H spp general field conditions natural soybean (Bt and non-Bt) Strategies for prevention of insectresistance Low presence of H spp in Bt soybean and refuge

[19] S spp H spp general field conditions natural soybean (Bt and non-Bt) Behavior of Bt soybean on the pestsand its predators

Bt soybean provided a good control of S spp andH spp and did not affect its predators

[18] Se individual controlled artificial soybean cultivars (non-Bt) Development survival andreproductive capacity

The development of Se was affected by thecultivar

[73] Sf Se Sa Sc individual controlled artificial diet Susceptibility to chlorantraniliproleand flubendiamide

Chlorantraniliprole showed a higher mortalitythan flubendiamide for all Lepidoptera species

tested

[70] S spp Sf general field conditions natural soybean (Bt and non-Bt) Diversity composition andpopulation dynamics

Bt soybean reduced the target insect pests andfavored populations of natural enemies

[71] Sf Sc Hg individual field conditions natural soybean (Bt and non-Bt) Insect abundance Densities of the species were low in both treatment

[27] Sa controlled artificial diet Developmental parameters andhost plants

Complete detail of biological parameters of Sa and55 host plant species of Sa are listed

[26] Se individual controlled artificial diet Biotic potential and reproductiveparameters

Complete detail of reproductive and populationparameters of Se

[28] Se individual controlled artificial diet Developmental parameters andhost plants

Complete detail of biological parameters of Se and202 host plant species of Se are listed

[29] Sa controlled artificial diet Biotic potential life tableparameters and fertility

Complete detail of reproductive and populationparameters of Sa

Insects 2018 9 93 4 of 13

Table 1 Cont

Study Species Identity ofSpecies

EnvironmentalConditions

(Controlled or FieldConditions)

Type ofInfestation Crop or Artificial Diet Used Evaluations Impacts

[72] Sf Sc Hg individual field conditions natural soybean (Bt and non-Bt) Strategies of refuge management

The management of refuges with selectiveinsecticides and high persistence allowed to

reduce the number of applications and to achievegreater survival of predators and adults of target

pests

[15] Se individual controlled artificial cotton soybean and Ipomoeagrandifolia (L) (Convolvulaceae) Biology on different host plant

Soybean was the least suitable for thedevelopment of Se and I grandifolia was shown a

suitable alternate host for Se

[20] Sc individual controlled artificial corn (Bt and non-Bt) soybean (Btand non-Bt) and diet Development and reproduction

Bt and non-Bt corn adversely affect thedevelopment of Sc and Bt soybean did not affectits biology suggesting that Sc has major potentialto become an important pest in Bt soybean crops

[76] Se Sc individual controlled artificialsoybean cotton corn Triticumaestivum (L) (Poaceae) Avena

sativa (L) and dietBiology on different host plants Soybean and cotton were more suitable hosts for

the development of Se and Sc

Species (only the species involved in the present study are mentioned) S spp Spodoptera species Sf S frugiperda Se S eridania Sa S albula Sc S cosmioides H spp Helicoverpa speciesHg H gelotopoeon General specific identity of each species was not considered in the study Individual specific identity of each species was considered in the study

Insects 2018 9 93 5 of 13

Helicoverpa gelotopoeon is another major pest of soybean Larvae of this species cause damage inthe vegetative and reproductive plant growth stages In Tucumaacuten and other provinces of Argentinathis species causes severe damage to soybean and chickpea (Cicer arietinum L (Fabaceae)) crops and canbe difficult to control with insecticides [50ndash53] Some other species of Helicoverpa such as H armigeraHuumlbner and H zea have also developed resistance to insecticides and Cry proteins [54ndash59]

Previous studies were conducted under field conditions considering the Helicoverpa genus ingeneral [7819] This has led to much speculation given the coexistence of H gelotopoeon and H armigerain soybean crops in northwestern Argentina [52] In this genus species can only be separated bymorphological characters of the adults [50] Thus the study of H gelotopoeon performance is importantto know the real potential of defoliation in soybean crops

The great potential for defoliation of soybean plants [1620] and damage to flowers and pods [14]by Spodoptera spp and H gelotopoeon [5152] requires the adoption of control tactics to prevent yield lossControl is achieved with insecticides often indirectly as result of sprays for A gemmatalis C includensand R nu [5ndash860]

The rapid adoption of Bt soybean in Argentina [2] and other countries in South America [61] hasincreased the need to know the behavior of nontarget and target pests of Bt soybean The objectiveof this study was to evaluate the performance of soybean expressing Cry1Ac against differentlepidopteran nontarget and target insect pests and to compare its performance with that of a non-Btsoybean with seed treatment We addressed this study by evaluating the defoliation produced bydifferent lepidopteran pests recorded at eight days after infestation

2 Materials and Methods

21 Larval Collection

Larvae of H gelotopoeon S albula S cosmiodes S eridania and S frugiperda were collected fromJanuary to March 2014 in commercial soybean fields in La Cocha (Dpto La Cocha) and Overo Pozo(Dpto Cruz Alta) counties in Tucumaacuten province (Argentina) A minimum of 250 larvae (from 3rd to6th instars) of each species were collected using a vertical beat sheet [62] Then each larva was placedin a glass tube (12 cm H and 15 cm D) with leaves of soybean and transported to our laboratoriesat the Estacioacuten Experimental Agroindustrial Obispo Colombres (EEAOC) The collected larvae wereplaced in growth chambers under controlled conditions (27 plusmn 2 C 70 plusmn 5 RH 1410 h LD) untiladult emergence Late larval instars and adults were examined using morphological characters bothto confirm the identity of species [47496364] and to establish pure cultures for each species in thelaboratory Voucher specimens for each species were deposited in the collection of Seccioacuten ZoologiacuteaAgriacutecola (EEAOC) Tucumaacuten Argentina

22 Insect Rearing

Each species colony was maintained in the same chamber under identically controlled conditionsat 27 plusmn 2 C 70 plusmn 5 RH 1410 h LD Colonies were reared according to the methodologydescribed by Muruacutea et al [65] and Herrero et al [53] Twenty-five pairs per cage and per species(25 females and 25 males) (N = 6) were used Adults were maintained in cylindrical ovipositioncages made out of plastic mesh (20 cm high and 15 cm in diameter) lined with polyethylene bagsas an oviposition substrate For aeration both ends of the cage were covered with a nylon clothThe food was provided via a cotton plug saturated with a mixture of honey and water (11 vv)which was replaced every day Cages were checked daily for oviposition and adult mortality Eggswere collected daily with a moistened brush and deposited in Petri dishes lined with moistenedfilter paper Once emerged neonate larvae were placed in 20-cm diameter 800-mL containerswith an artificial larval diet that included bean flour (Grandietreg Buenos Aires Argentina) wheatgerm (Grandietreg Buenos Aires Argentina) brewerrsquos yeast (Calsareg Tucumaacuten Argentina) vitaminC (Anedrareg Buenos Aires Argentina) sorbic acid (Anedrareg Buenos Aires Argentina) vitamin

Insects 2018 9 93 6 of 13

supplement amino acids (Ruminalreg Buenos Aires Argentina) and methylparaben (Todo DrogaregCoacuterdoba Argentina) Diet was replaced every five days As larvae pupated pupae were sexed andplaced in cup containers with moistened filter paper until adultrsquos emergence Adults were used toinitiate a new generation After establishing a colony for each species individuals from the 2ndgeneration (F2) were used for the evaluation of soybean Cry1Ac against different pest species ina greenhouse

23 Greenhouse Studies

Soybean seeds of maturity group 7 were used (recommended for cultivation in northwesternArgentina) The treatments evaluated were Bt soybean Cry1Ac (T1) non-Bt soybean plus seedtreatment (T2) (Fortenzareg diamide insecticide Syngenta Argentina) according to the doseraterecommended by the company (36 g ai100 Kgseed) and non-Bt soybean without seed treatmentas an untreated control (T3) The three treatments were planted in different pots (15 cm D 600 mL)using sterilized soil One seed per pot was planted and each plant was labeled to distinguish boththe species and treatment The plants were maintained under greenhouse conditions under ambientlighting at approximately 33 plusmn 4 C 80 plusmn 10 RH 1410 h LD

The experimental design was completely randomized with three replicates per treatmentwhere each replicate consisted of 20 soybean plants A total of 60 plants for each pest species (5)per treatment (3) were evaluated resulting in 900 plants

Each plant for each treatment was inoculated at the V1 stage [66] (approximately 14 days afterplanting) with 10 larvae (L1) of a pest species The evaluations of defoliation produced by each specieswere recorded at 8 days after inoculation (DAI) according the visual estimation of defoliation scaledescribed by Kogan and Turnipseed [67]

Expression of the Cry1Ac protein in the soybean plants was confirmed using qualitative ELISAQuickstix lateral flow detection strips (Envirologix Portland ME USA)

24 Data Analysis

To meet parametric assumptions percentage data on defoliation damage were transformed toarcsine square root prior to analysis [68] nevertheless untransformed means (plusmnSE) are shown in thefigure The percentage of defoliation damage produced by each species in the different treatments andthe performance of these species using non-Bt soybean without seed treatment were analyzed using aone-way ANOVA and means were separated using Tukeyrsquos tests (p lt 005) with InfoStat [69]

3 Results

All results are shown in Figure 1 Significant differences were found in the average defoliationdamage produced by H gelotopoeon among different treatments (F = 643 df = 2177 p lt 00001)Bt soybean (T1) and non-Bt soybean plus Fortenzareg (T2) presented similar values but significantdifferences were found when they were compared with the control (T3) The average defoliationdamage produced by S albula was lower in the Bt soybean and non-Bt soybean plus Fortenzareg

treatments compared to the control (Figure 1) (F = 1110 df = 2177 p lt 00001) For S cosmiodes lowerfeeding damage was recorded in the non-Bt soybean plus Fortenzareg treatment compared to the Btsoybean and control plants (F = 760 df = 2176 p lt 00001) The best control of S eridania was with thenon-Bt soybean plus Fortenzareg treatment registering a lower percentage of defoliation compared toBt soybean and the control plants (F = 2691 df = 2177 p lt 00001) Finally significant differences werefound in the percentage of defoliation produced by S frugiperda in the different treatments (F = 947df = 2177 p lt 00001) The lowest defoliation was obtained with non-Bt soybean plus Fortenzareg

(057 plusmn 012) whereas the control plants showed the highest defoliationA comparison of the potential risk of these species on untreated plants (non-Bt soybean without

seed treatment) showed significant differences (F = 1009 df = 4293 p lt 00001) The highest defoliation

Insects 2018 9 93 7 of 13

damage was produced by S eridania larvae (393 plusmn 189) followed by S albula (102 plusmn 097) S cosmiodes(91 plusmn 079) S frugiperda (67 plusmn 054) and H gelotopoeon (48 plusmn 043)Insects 2018 9 x FOR PEER REVIEW 7 of 13

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albula Spodoptera

cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae in different

soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Bt soybean

without seed treatment) Means plusmn SE within species accompanied by different letters indicate

significant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac against H

gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performance with that

of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On the other hand the

performance analysis made among the species using non-Bt soybean without seed treatment

showed which of these species would represent a potential risk for soybean crops For both analyses

the defoliation and potential risk were calculated considering the identity for each species in

greenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This

new technology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S

albula

Non-Bt soybean with seed treatment provided good control of the five species Nevertheless

this control will be only for the early plant growth stage when plants have more insecticide active

ingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in the

lowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and the

differences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and Argentina A

study of diversity composition and population dynamics of arthropods in non-Bt soybean and Bt

soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantly

controlled by Bt soybean However other species of the Spodoptera complex were not controlled by

this technology [70] Other studies reported that S cosmiodes was the most abundant species

attacking Bt soybean [71] and that development and reproduction of this species were not affected

by the Cry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the

soybean cycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the

population abundance of the last two species was similar in Bt and non-Bt soybean In northwestern

Argentina a trial conducted to evaluate Bt soybean against different insect pest and natural

predators found that this new technology provided good control of target pests such as A

gemmatalis C includens and R nu The levels of leaf damage observed with Bt soybean were lowest

and significantly different to those obtained with non-Bt soybean [4] On the other hand bioassays

and greenhouse studies found that S cosmiodes S eridania and S frugiperda exhibited low to no

susceptibility to MON 87701 times MON 89788 soybean containing the protein Cry1Ac and these species

showed higher tolerance to the Cry1Ac protein than other Lepidoptera species such as C includens

a a

b

b

ba a aa

a

b

b c

c

c

0

5

10

15

20

25

30

35

40

45

H gelotopoeon S albula S cosmiodes S eridania S frugiperda

Me

an

(plusmn

SE

) p

erc

en

tag

e o

f d

efo

lia

tio

n

T1 T2 T3

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albulaSpodoptera cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae indifferent soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Btsoybean without seed treatment) Means plusmn SE within species accompanied by different letters indicatesignificant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac againstH gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performancewith that of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On theother hand the performance analysis made among the species using non-Bt soybean without seedtreatment showed which of these species would represent a potential risk for soybean crops For bothanalyses the defoliation and potential risk were calculated considering the identity for each species ingreenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This newtechnology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S albula

Non-Bt soybean with seed treatment provided good control of the five species Neverthelessthis control will be only for the early plant growth stage when plants have more insecticide activeingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in thelowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and thedifferences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and ArgentinaA study of diversity composition and population dynamics of arthropods in non-Bt soybean andBt soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantlycontrolled by Bt soybean However other species of the Spodoptera complex were not controlled bythis technology [70] Other studies reported that S cosmiodes was the most abundant species attackingBt soybean [71] and that development and reproduction of this species were not affected by theCry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the soybeancycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the populationabundance of the last two species was similar in Bt and non-Bt soybean In northwestern Argentinaa trial conducted to evaluate Bt soybean against different insect pest and natural predators foundthat this new technology provided good control of target pests such as A gemmatalis C includens

Insects 2018 9 93 8 of 13

and R nu The levels of leaf damage observed with Bt soybean were lowest and significantly differentto those obtained with non-Bt soybean [4] On the other hand bioassays and greenhouse studiesfound that S cosmiodes S eridania and S frugiperda exhibited low to no susceptibility to MON 87701 timesMON 89788 soybean containing the protein Cry1Ac and these species showed higher tolerance tothe Cry1Ac protein than other Lepidoptera species such as C includens C virescens and H zea [60]In the same study a moderate larval incidence of S eridania and S frugiperda on MON 87701 x MON89788 soybean and the respective near-isogenic negative check was found No significant differencesin larval incidence and defoliation by S eridania were found with Bt soybean and the near-isogenicnegative checks for both maturity groups Similarly larval incidence of S frugiperda on Bt soybeandid not differ significantly from the respective near-isogenic negative checks for both maturity groupsHowever defoliation by S frugiperda on Bt soybean was significantly lower than on the near-isogenicbeing the defoliation registered similar to those reported in this study in Bt soybean The defoliationrecorded for S eridania was different to those reported in greenhouse studies in Brazil [60] but in bothstudies defoliation was high in non-Bt soybean These differences could be due to the number oflarvae used to evaluate the defoliation per plants

The non-Bt soybean with seed treatment showed the lowest defoliation of S frugiperda S albulaS cosmiodes and S eridania These results are similar to another study [73] where diamides had goodpotential to control different lepidopteran pests such as S eridania S cosmiodes S albula A gemmatalisand S frugiperda

Considering the performance of each species using non-Bt soybean without seed treatmentH gelotopoeon showed the lowest defoliation This species is one of the most important pests insoybean crops but its larvae prefer the reproductive plant growth stages [5074] which explains thelow defoliation recorded in this study As mentioned Spodoptera spp are polyphagous but showpreferences to different host plants such as the preference of S frugiperda to corn (Zea mays L (Poaceae))over soybean and other crops [75] Spodoptera cosmiodes and S albula presented similar levels ofdefoliation in our test although S cosmiodes is the most frequent Spodoptera spp affecting soybeancrops during the vegetative and reproductive stages [5614162050] Another study suggested thatS cosmioides may be more adapted to chemical compounds of soybean and cotton (Gossypium hirsutumL (Malvaceae)) given their faster development and higher survival rates on these hosts [76] Larvaeof S albula feed on a wide variety of host plants and they also exhibit some preference for severalweeds (Boerhavia erecta (L) (Nyctaginaceae) Echinochloa colonum (L) Link (Poaceae) from whichthey can migrate to cultivated plants [2729] The highest defoliation damage was produced byS eridania This species had been cited as infesting a large number of crops in various regions ofthe Americas [497477] Additionally this species has been reported from outbreaks under differentconditions [151828] This species develops on weeds which generally constitute a primary source ofcultivated plant infestations such as those of soybean [152628] Considering the defoliation recordedin this study S eridania would represent a potential risk to soybean crops According to these resultsthis species may be more adapted to chemical compounds of soybean given their faster developmentand higher survival rates [76]

5 Conclusions

Our results suggest that H gelotopoeon S frugiperda and S albula were susceptible to the Cry1Acprotein However S eridania and S cosmiodes were not susceptible to the Cry1Ac protein in MON87701 times MON 89788 soybean when evaluated by greenhouse infestation supporting the idea that thelevel of activity of this protein against these species is low Consequently other control tactics such asseed treatment must be used in combination with MON 87701 times MON 89788 soybean in the field forthe efficient management of Spodoptera species

Our results contribute to determining the defoliation and potential risk of these pests in soybeancrops Considering the increasing importance of S cosmioides and S eridania in the region future studiesshould be focused toward understanding survival population dynamics and infestation of these

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 3 of 13

Table 1 Summary of previous studies of the Spodoptera complex and Helicoverpa gelotopoeon (Lep Noctuidae) where the performance of each species was evaluatedusing different crops andor artificial diet in field and laboratory studies

Study Species Identity ofSpecies

EnvironmentalConditions

(Controlled or FieldConditions)

Type ofInfestation Crop or Artificial Diet Used Evaluations Impacts

Present study Sf Se Sa Sc Hg individual controlled(greenhouse) artificial soybean (Bt and non-Bt) Performance and potencial risk

Bt soybean had the best control of Hg and asuppressive effect on Sf and Sa Se and Sc were

not susceptible to the Bt soybean Se represents apotential risk in soybean crops

[60] Sc Se Sf individual controlled artificial soybean (Bt and non-Bt) and diet Susceptibility to Cry1Ac protein Bt soybean showed poor control of Sc Se Sf

[16] Sf Se Sc individual controlled artificial soybean genotypes Larva consumption foliage Sc defoliated nearly twice the leaf area of Sa and Sf

[5] S spp general field conditions natural soybeanDifferent chemical alternatives forthe management of the complex

pestDiamide + neonicotinoid had the best control

[6] Sc individual field conditions natural soybean Moment of application of differentinsecticides

Early application of diamide delayed the damageof larvae

[7] H spp S spp general field conditions natural soybean (Bt and non-Bt) Pest management Early application of diamide delayed the damageof larvae

[8] H spp general field conditions natural soybean (Bt and non-Bt) Strategies for prevention of insectresistance Low presence of H spp in Bt soybean and refuge

[19] S spp H spp general field conditions natural soybean (Bt and non-Bt) Behavior of Bt soybean on the pestsand its predators

Bt soybean provided a good control of S spp andH spp and did not affect its predators

[18] Se individual controlled artificial soybean cultivars (non-Bt) Development survival andreproductive capacity

The development of Se was affected by thecultivar

[73] Sf Se Sa Sc individual controlled artificial diet Susceptibility to chlorantraniliproleand flubendiamide

Chlorantraniliprole showed a higher mortalitythan flubendiamide for all Lepidoptera species

tested

[70] S spp Sf general field conditions natural soybean (Bt and non-Bt) Diversity composition andpopulation dynamics

Bt soybean reduced the target insect pests andfavored populations of natural enemies

[71] Sf Sc Hg individual field conditions natural soybean (Bt and non-Bt) Insect abundance Densities of the species were low in both treatment

[27] Sa controlled artificial diet Developmental parameters andhost plants

Complete detail of biological parameters of Sa and55 host plant species of Sa are listed

[26] Se individual controlled artificial diet Biotic potential and reproductiveparameters

Complete detail of reproductive and populationparameters of Se

[28] Se individual controlled artificial diet Developmental parameters andhost plants

Complete detail of biological parameters of Se and202 host plant species of Se are listed

[29] Sa controlled artificial diet Biotic potential life tableparameters and fertility

Complete detail of reproductive and populationparameters of Sa

Insects 2018 9 93 4 of 13

Table 1 Cont

Study Species Identity ofSpecies

EnvironmentalConditions

(Controlled or FieldConditions)

Type ofInfestation Crop or Artificial Diet Used Evaluations Impacts

[72] Sf Sc Hg individual field conditions natural soybean (Bt and non-Bt) Strategies of refuge management

The management of refuges with selectiveinsecticides and high persistence allowed to

reduce the number of applications and to achievegreater survival of predators and adults of target

pests

[15] Se individual controlled artificial cotton soybean and Ipomoeagrandifolia (L) (Convolvulaceae) Biology on different host plant

Soybean was the least suitable for thedevelopment of Se and I grandifolia was shown a

suitable alternate host for Se

[20] Sc individual controlled artificial corn (Bt and non-Bt) soybean (Btand non-Bt) and diet Development and reproduction

Bt and non-Bt corn adversely affect thedevelopment of Sc and Bt soybean did not affectits biology suggesting that Sc has major potentialto become an important pest in Bt soybean crops

[76] Se Sc individual controlled artificialsoybean cotton corn Triticumaestivum (L) (Poaceae) Avena

sativa (L) and dietBiology on different host plants Soybean and cotton were more suitable hosts for

the development of Se and Sc

Species (only the species involved in the present study are mentioned) S spp Spodoptera species Sf S frugiperda Se S eridania Sa S albula Sc S cosmioides H spp Helicoverpa speciesHg H gelotopoeon General specific identity of each species was not considered in the study Individual specific identity of each species was considered in the study

Insects 2018 9 93 5 of 13

Helicoverpa gelotopoeon is another major pest of soybean Larvae of this species cause damage inthe vegetative and reproductive plant growth stages In Tucumaacuten and other provinces of Argentinathis species causes severe damage to soybean and chickpea (Cicer arietinum L (Fabaceae)) crops and canbe difficult to control with insecticides [50ndash53] Some other species of Helicoverpa such as H armigeraHuumlbner and H zea have also developed resistance to insecticides and Cry proteins [54ndash59]

Previous studies were conducted under field conditions considering the Helicoverpa genus ingeneral [7819] This has led to much speculation given the coexistence of H gelotopoeon and H armigerain soybean crops in northwestern Argentina [52] In this genus species can only be separated bymorphological characters of the adults [50] Thus the study of H gelotopoeon performance is importantto know the real potential of defoliation in soybean crops

The great potential for defoliation of soybean plants [1620] and damage to flowers and pods [14]by Spodoptera spp and H gelotopoeon [5152] requires the adoption of control tactics to prevent yield lossControl is achieved with insecticides often indirectly as result of sprays for A gemmatalis C includensand R nu [5ndash860]

The rapid adoption of Bt soybean in Argentina [2] and other countries in South America [61] hasincreased the need to know the behavior of nontarget and target pests of Bt soybean The objectiveof this study was to evaluate the performance of soybean expressing Cry1Ac against differentlepidopteran nontarget and target insect pests and to compare its performance with that of a non-Btsoybean with seed treatment We addressed this study by evaluating the defoliation produced bydifferent lepidopteran pests recorded at eight days after infestation

2 Materials and Methods

21 Larval Collection

Larvae of H gelotopoeon S albula S cosmiodes S eridania and S frugiperda were collected fromJanuary to March 2014 in commercial soybean fields in La Cocha (Dpto La Cocha) and Overo Pozo(Dpto Cruz Alta) counties in Tucumaacuten province (Argentina) A minimum of 250 larvae (from 3rd to6th instars) of each species were collected using a vertical beat sheet [62] Then each larva was placedin a glass tube (12 cm H and 15 cm D) with leaves of soybean and transported to our laboratoriesat the Estacioacuten Experimental Agroindustrial Obispo Colombres (EEAOC) The collected larvae wereplaced in growth chambers under controlled conditions (27 plusmn 2 C 70 plusmn 5 RH 1410 h LD) untiladult emergence Late larval instars and adults were examined using morphological characters bothto confirm the identity of species [47496364] and to establish pure cultures for each species in thelaboratory Voucher specimens for each species were deposited in the collection of Seccioacuten ZoologiacuteaAgriacutecola (EEAOC) Tucumaacuten Argentina

22 Insect Rearing

Each species colony was maintained in the same chamber under identically controlled conditionsat 27 plusmn 2 C 70 plusmn 5 RH 1410 h LD Colonies were reared according to the methodologydescribed by Muruacutea et al [65] and Herrero et al [53] Twenty-five pairs per cage and per species(25 females and 25 males) (N = 6) were used Adults were maintained in cylindrical ovipositioncages made out of plastic mesh (20 cm high and 15 cm in diameter) lined with polyethylene bagsas an oviposition substrate For aeration both ends of the cage were covered with a nylon clothThe food was provided via a cotton plug saturated with a mixture of honey and water (11 vv)which was replaced every day Cages were checked daily for oviposition and adult mortality Eggswere collected daily with a moistened brush and deposited in Petri dishes lined with moistenedfilter paper Once emerged neonate larvae were placed in 20-cm diameter 800-mL containerswith an artificial larval diet that included bean flour (Grandietreg Buenos Aires Argentina) wheatgerm (Grandietreg Buenos Aires Argentina) brewerrsquos yeast (Calsareg Tucumaacuten Argentina) vitaminC (Anedrareg Buenos Aires Argentina) sorbic acid (Anedrareg Buenos Aires Argentina) vitamin

Insects 2018 9 93 6 of 13

supplement amino acids (Ruminalreg Buenos Aires Argentina) and methylparaben (Todo DrogaregCoacuterdoba Argentina) Diet was replaced every five days As larvae pupated pupae were sexed andplaced in cup containers with moistened filter paper until adultrsquos emergence Adults were used toinitiate a new generation After establishing a colony for each species individuals from the 2ndgeneration (F2) were used for the evaluation of soybean Cry1Ac against different pest species ina greenhouse

23 Greenhouse Studies

Soybean seeds of maturity group 7 were used (recommended for cultivation in northwesternArgentina) The treatments evaluated were Bt soybean Cry1Ac (T1) non-Bt soybean plus seedtreatment (T2) (Fortenzareg diamide insecticide Syngenta Argentina) according to the doseraterecommended by the company (36 g ai100 Kgseed) and non-Bt soybean without seed treatmentas an untreated control (T3) The three treatments were planted in different pots (15 cm D 600 mL)using sterilized soil One seed per pot was planted and each plant was labeled to distinguish boththe species and treatment The plants were maintained under greenhouse conditions under ambientlighting at approximately 33 plusmn 4 C 80 plusmn 10 RH 1410 h LD

The experimental design was completely randomized with three replicates per treatmentwhere each replicate consisted of 20 soybean plants A total of 60 plants for each pest species (5)per treatment (3) were evaluated resulting in 900 plants

Each plant for each treatment was inoculated at the V1 stage [66] (approximately 14 days afterplanting) with 10 larvae (L1) of a pest species The evaluations of defoliation produced by each specieswere recorded at 8 days after inoculation (DAI) according the visual estimation of defoliation scaledescribed by Kogan and Turnipseed [67]

Expression of the Cry1Ac protein in the soybean plants was confirmed using qualitative ELISAQuickstix lateral flow detection strips (Envirologix Portland ME USA)

24 Data Analysis

To meet parametric assumptions percentage data on defoliation damage were transformed toarcsine square root prior to analysis [68] nevertheless untransformed means (plusmnSE) are shown in thefigure The percentage of defoliation damage produced by each species in the different treatments andthe performance of these species using non-Bt soybean without seed treatment were analyzed using aone-way ANOVA and means were separated using Tukeyrsquos tests (p lt 005) with InfoStat [69]

3 Results

All results are shown in Figure 1 Significant differences were found in the average defoliationdamage produced by H gelotopoeon among different treatments (F = 643 df = 2177 p lt 00001)Bt soybean (T1) and non-Bt soybean plus Fortenzareg (T2) presented similar values but significantdifferences were found when they were compared with the control (T3) The average defoliationdamage produced by S albula was lower in the Bt soybean and non-Bt soybean plus Fortenzareg

treatments compared to the control (Figure 1) (F = 1110 df = 2177 p lt 00001) For S cosmiodes lowerfeeding damage was recorded in the non-Bt soybean plus Fortenzareg treatment compared to the Btsoybean and control plants (F = 760 df = 2176 p lt 00001) The best control of S eridania was with thenon-Bt soybean plus Fortenzareg treatment registering a lower percentage of defoliation compared toBt soybean and the control plants (F = 2691 df = 2177 p lt 00001) Finally significant differences werefound in the percentage of defoliation produced by S frugiperda in the different treatments (F = 947df = 2177 p lt 00001) The lowest defoliation was obtained with non-Bt soybean plus Fortenzareg

(057 plusmn 012) whereas the control plants showed the highest defoliationA comparison of the potential risk of these species on untreated plants (non-Bt soybean without

seed treatment) showed significant differences (F = 1009 df = 4293 p lt 00001) The highest defoliation

Insects 2018 9 93 7 of 13

damage was produced by S eridania larvae (393 plusmn 189) followed by S albula (102 plusmn 097) S cosmiodes(91 plusmn 079) S frugiperda (67 plusmn 054) and H gelotopoeon (48 plusmn 043)Insects 2018 9 x FOR PEER REVIEW 7 of 13

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albula Spodoptera

cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae in different

soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Bt soybean

without seed treatment) Means plusmn SE within species accompanied by different letters indicate

significant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac against H

gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performance with that

of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On the other hand the

performance analysis made among the species using non-Bt soybean without seed treatment

showed which of these species would represent a potential risk for soybean crops For both analyses

the defoliation and potential risk were calculated considering the identity for each species in

greenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This

new technology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S

albula

Non-Bt soybean with seed treatment provided good control of the five species Nevertheless

this control will be only for the early plant growth stage when plants have more insecticide active

ingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in the

lowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and the

differences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and Argentina A

study of diversity composition and population dynamics of arthropods in non-Bt soybean and Bt

soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantly

controlled by Bt soybean However other species of the Spodoptera complex were not controlled by

this technology [70] Other studies reported that S cosmiodes was the most abundant species

attacking Bt soybean [71] and that development and reproduction of this species were not affected

by the Cry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the

soybean cycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the

population abundance of the last two species was similar in Bt and non-Bt soybean In northwestern

Argentina a trial conducted to evaluate Bt soybean against different insect pest and natural

predators found that this new technology provided good control of target pests such as A

gemmatalis C includens and R nu The levels of leaf damage observed with Bt soybean were lowest

and significantly different to those obtained with non-Bt soybean [4] On the other hand bioassays

and greenhouse studies found that S cosmiodes S eridania and S frugiperda exhibited low to no

susceptibility to MON 87701 times MON 89788 soybean containing the protein Cry1Ac and these species

showed higher tolerance to the Cry1Ac protein than other Lepidoptera species such as C includens

a a

b

b

ba a aa

a

b

b c

c

c

0

5

10

15

20

25

30

35

40

45

H gelotopoeon S albula S cosmiodes S eridania S frugiperda

Me

an

(plusmn

SE

) p

erc

en

tag

e o

f d

efo

lia

tio

n

T1 T2 T3

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albulaSpodoptera cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae indifferent soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Btsoybean without seed treatment) Means plusmn SE within species accompanied by different letters indicatesignificant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac againstH gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performancewith that of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On theother hand the performance analysis made among the species using non-Bt soybean without seedtreatment showed which of these species would represent a potential risk for soybean crops For bothanalyses the defoliation and potential risk were calculated considering the identity for each species ingreenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This newtechnology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S albula

Non-Bt soybean with seed treatment provided good control of the five species Neverthelessthis control will be only for the early plant growth stage when plants have more insecticide activeingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in thelowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and thedifferences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and ArgentinaA study of diversity composition and population dynamics of arthropods in non-Bt soybean andBt soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantlycontrolled by Bt soybean However other species of the Spodoptera complex were not controlled bythis technology [70] Other studies reported that S cosmiodes was the most abundant species attackingBt soybean [71] and that development and reproduction of this species were not affected by theCry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the soybeancycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the populationabundance of the last two species was similar in Bt and non-Bt soybean In northwestern Argentinaa trial conducted to evaluate Bt soybean against different insect pest and natural predators foundthat this new technology provided good control of target pests such as A gemmatalis C includens

Insects 2018 9 93 8 of 13

and R nu The levels of leaf damage observed with Bt soybean were lowest and significantly differentto those obtained with non-Bt soybean [4] On the other hand bioassays and greenhouse studiesfound that S cosmiodes S eridania and S frugiperda exhibited low to no susceptibility to MON 87701 timesMON 89788 soybean containing the protein Cry1Ac and these species showed higher tolerance tothe Cry1Ac protein than other Lepidoptera species such as C includens C virescens and H zea [60]In the same study a moderate larval incidence of S eridania and S frugiperda on MON 87701 x MON89788 soybean and the respective near-isogenic negative check was found No significant differencesin larval incidence and defoliation by S eridania were found with Bt soybean and the near-isogenicnegative checks for both maturity groups Similarly larval incidence of S frugiperda on Bt soybeandid not differ significantly from the respective near-isogenic negative checks for both maturity groupsHowever defoliation by S frugiperda on Bt soybean was significantly lower than on the near-isogenicbeing the defoliation registered similar to those reported in this study in Bt soybean The defoliationrecorded for S eridania was different to those reported in greenhouse studies in Brazil [60] but in bothstudies defoliation was high in non-Bt soybean These differences could be due to the number oflarvae used to evaluate the defoliation per plants

The non-Bt soybean with seed treatment showed the lowest defoliation of S frugiperda S albulaS cosmiodes and S eridania These results are similar to another study [73] where diamides had goodpotential to control different lepidopteran pests such as S eridania S cosmiodes S albula A gemmatalisand S frugiperda

Considering the performance of each species using non-Bt soybean without seed treatmentH gelotopoeon showed the lowest defoliation This species is one of the most important pests insoybean crops but its larvae prefer the reproductive plant growth stages [5074] which explains thelow defoliation recorded in this study As mentioned Spodoptera spp are polyphagous but showpreferences to different host plants such as the preference of S frugiperda to corn (Zea mays L (Poaceae))over soybean and other crops [75] Spodoptera cosmiodes and S albula presented similar levels ofdefoliation in our test although S cosmiodes is the most frequent Spodoptera spp affecting soybeancrops during the vegetative and reproductive stages [5614162050] Another study suggested thatS cosmioides may be more adapted to chemical compounds of soybean and cotton (Gossypium hirsutumL (Malvaceae)) given their faster development and higher survival rates on these hosts [76] Larvaeof S albula feed on a wide variety of host plants and they also exhibit some preference for severalweeds (Boerhavia erecta (L) (Nyctaginaceae) Echinochloa colonum (L) Link (Poaceae) from whichthey can migrate to cultivated plants [2729] The highest defoliation damage was produced byS eridania This species had been cited as infesting a large number of crops in various regions ofthe Americas [497477] Additionally this species has been reported from outbreaks under differentconditions [151828] This species develops on weeds which generally constitute a primary source ofcultivated plant infestations such as those of soybean [152628] Considering the defoliation recordedin this study S eridania would represent a potential risk to soybean crops According to these resultsthis species may be more adapted to chemical compounds of soybean given their faster developmentand higher survival rates [76]

5 Conclusions

Our results suggest that H gelotopoeon S frugiperda and S albula were susceptible to the Cry1Acprotein However S eridania and S cosmiodes were not susceptible to the Cry1Ac protein in MON87701 times MON 89788 soybean when evaluated by greenhouse infestation supporting the idea that thelevel of activity of this protein against these species is low Consequently other control tactics such asseed treatment must be used in combination with MON 87701 times MON 89788 soybean in the field forthe efficient management of Spodoptera species

Our results contribute to determining the defoliation and potential risk of these pests in soybeancrops Considering the increasing importance of S cosmioides and S eridania in the region future studiesshould be focused toward understanding survival population dynamics and infestation of these

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 4 of 13

Table 1 Cont

Study Species Identity ofSpecies

EnvironmentalConditions

(Controlled or FieldConditions)

Type ofInfestation Crop or Artificial Diet Used Evaluations Impacts

[72] Sf Sc Hg individual field conditions natural soybean (Bt and non-Bt) Strategies of refuge management

The management of refuges with selectiveinsecticides and high persistence allowed to

reduce the number of applications and to achievegreater survival of predators and adults of target

pests

[15] Se individual controlled artificial cotton soybean and Ipomoeagrandifolia (L) (Convolvulaceae) Biology on different host plant

Soybean was the least suitable for thedevelopment of Se and I grandifolia was shown a

suitable alternate host for Se

[20] Sc individual controlled artificial corn (Bt and non-Bt) soybean (Btand non-Bt) and diet Development and reproduction

Bt and non-Bt corn adversely affect thedevelopment of Sc and Bt soybean did not affectits biology suggesting that Sc has major potentialto become an important pest in Bt soybean crops

[76] Se Sc individual controlled artificialsoybean cotton corn Triticumaestivum (L) (Poaceae) Avena

sativa (L) and dietBiology on different host plants Soybean and cotton were more suitable hosts for

the development of Se and Sc

Species (only the species involved in the present study are mentioned) S spp Spodoptera species Sf S frugiperda Se S eridania Sa S albula Sc S cosmioides H spp Helicoverpa speciesHg H gelotopoeon General specific identity of each species was not considered in the study Individual specific identity of each species was considered in the study

Insects 2018 9 93 5 of 13

Helicoverpa gelotopoeon is another major pest of soybean Larvae of this species cause damage inthe vegetative and reproductive plant growth stages In Tucumaacuten and other provinces of Argentinathis species causes severe damage to soybean and chickpea (Cicer arietinum L (Fabaceae)) crops and canbe difficult to control with insecticides [50ndash53] Some other species of Helicoverpa such as H armigeraHuumlbner and H zea have also developed resistance to insecticides and Cry proteins [54ndash59]

Previous studies were conducted under field conditions considering the Helicoverpa genus ingeneral [7819] This has led to much speculation given the coexistence of H gelotopoeon and H armigerain soybean crops in northwestern Argentina [52] In this genus species can only be separated bymorphological characters of the adults [50] Thus the study of H gelotopoeon performance is importantto know the real potential of defoliation in soybean crops

The great potential for defoliation of soybean plants [1620] and damage to flowers and pods [14]by Spodoptera spp and H gelotopoeon [5152] requires the adoption of control tactics to prevent yield lossControl is achieved with insecticides often indirectly as result of sprays for A gemmatalis C includensand R nu [5ndash860]

The rapid adoption of Bt soybean in Argentina [2] and other countries in South America [61] hasincreased the need to know the behavior of nontarget and target pests of Bt soybean The objectiveof this study was to evaluate the performance of soybean expressing Cry1Ac against differentlepidopteran nontarget and target insect pests and to compare its performance with that of a non-Btsoybean with seed treatment We addressed this study by evaluating the defoliation produced bydifferent lepidopteran pests recorded at eight days after infestation

2 Materials and Methods

21 Larval Collection

Larvae of H gelotopoeon S albula S cosmiodes S eridania and S frugiperda were collected fromJanuary to March 2014 in commercial soybean fields in La Cocha (Dpto La Cocha) and Overo Pozo(Dpto Cruz Alta) counties in Tucumaacuten province (Argentina) A minimum of 250 larvae (from 3rd to6th instars) of each species were collected using a vertical beat sheet [62] Then each larva was placedin a glass tube (12 cm H and 15 cm D) with leaves of soybean and transported to our laboratoriesat the Estacioacuten Experimental Agroindustrial Obispo Colombres (EEAOC) The collected larvae wereplaced in growth chambers under controlled conditions (27 plusmn 2 C 70 plusmn 5 RH 1410 h LD) untiladult emergence Late larval instars and adults were examined using morphological characters bothto confirm the identity of species [47496364] and to establish pure cultures for each species in thelaboratory Voucher specimens for each species were deposited in the collection of Seccioacuten ZoologiacuteaAgriacutecola (EEAOC) Tucumaacuten Argentina

22 Insect Rearing

Each species colony was maintained in the same chamber under identically controlled conditionsat 27 plusmn 2 C 70 plusmn 5 RH 1410 h LD Colonies were reared according to the methodologydescribed by Muruacutea et al [65] and Herrero et al [53] Twenty-five pairs per cage and per species(25 females and 25 males) (N = 6) were used Adults were maintained in cylindrical ovipositioncages made out of plastic mesh (20 cm high and 15 cm in diameter) lined with polyethylene bagsas an oviposition substrate For aeration both ends of the cage were covered with a nylon clothThe food was provided via a cotton plug saturated with a mixture of honey and water (11 vv)which was replaced every day Cages were checked daily for oviposition and adult mortality Eggswere collected daily with a moistened brush and deposited in Petri dishes lined with moistenedfilter paper Once emerged neonate larvae were placed in 20-cm diameter 800-mL containerswith an artificial larval diet that included bean flour (Grandietreg Buenos Aires Argentina) wheatgerm (Grandietreg Buenos Aires Argentina) brewerrsquos yeast (Calsareg Tucumaacuten Argentina) vitaminC (Anedrareg Buenos Aires Argentina) sorbic acid (Anedrareg Buenos Aires Argentina) vitamin

Insects 2018 9 93 6 of 13

supplement amino acids (Ruminalreg Buenos Aires Argentina) and methylparaben (Todo DrogaregCoacuterdoba Argentina) Diet was replaced every five days As larvae pupated pupae were sexed andplaced in cup containers with moistened filter paper until adultrsquos emergence Adults were used toinitiate a new generation After establishing a colony for each species individuals from the 2ndgeneration (F2) were used for the evaluation of soybean Cry1Ac against different pest species ina greenhouse

23 Greenhouse Studies

Soybean seeds of maturity group 7 were used (recommended for cultivation in northwesternArgentina) The treatments evaluated were Bt soybean Cry1Ac (T1) non-Bt soybean plus seedtreatment (T2) (Fortenzareg diamide insecticide Syngenta Argentina) according to the doseraterecommended by the company (36 g ai100 Kgseed) and non-Bt soybean without seed treatmentas an untreated control (T3) The three treatments were planted in different pots (15 cm D 600 mL)using sterilized soil One seed per pot was planted and each plant was labeled to distinguish boththe species and treatment The plants were maintained under greenhouse conditions under ambientlighting at approximately 33 plusmn 4 C 80 plusmn 10 RH 1410 h LD

The experimental design was completely randomized with three replicates per treatmentwhere each replicate consisted of 20 soybean plants A total of 60 plants for each pest species (5)per treatment (3) were evaluated resulting in 900 plants

Each plant for each treatment was inoculated at the V1 stage [66] (approximately 14 days afterplanting) with 10 larvae (L1) of a pest species The evaluations of defoliation produced by each specieswere recorded at 8 days after inoculation (DAI) according the visual estimation of defoliation scaledescribed by Kogan and Turnipseed [67]

Expression of the Cry1Ac protein in the soybean plants was confirmed using qualitative ELISAQuickstix lateral flow detection strips (Envirologix Portland ME USA)

24 Data Analysis

To meet parametric assumptions percentage data on defoliation damage were transformed toarcsine square root prior to analysis [68] nevertheless untransformed means (plusmnSE) are shown in thefigure The percentage of defoliation damage produced by each species in the different treatments andthe performance of these species using non-Bt soybean without seed treatment were analyzed using aone-way ANOVA and means were separated using Tukeyrsquos tests (p lt 005) with InfoStat [69]

3 Results

All results are shown in Figure 1 Significant differences were found in the average defoliationdamage produced by H gelotopoeon among different treatments (F = 643 df = 2177 p lt 00001)Bt soybean (T1) and non-Bt soybean plus Fortenzareg (T2) presented similar values but significantdifferences were found when they were compared with the control (T3) The average defoliationdamage produced by S albula was lower in the Bt soybean and non-Bt soybean plus Fortenzareg

treatments compared to the control (Figure 1) (F = 1110 df = 2177 p lt 00001) For S cosmiodes lowerfeeding damage was recorded in the non-Bt soybean plus Fortenzareg treatment compared to the Btsoybean and control plants (F = 760 df = 2176 p lt 00001) The best control of S eridania was with thenon-Bt soybean plus Fortenzareg treatment registering a lower percentage of defoliation compared toBt soybean and the control plants (F = 2691 df = 2177 p lt 00001) Finally significant differences werefound in the percentage of defoliation produced by S frugiperda in the different treatments (F = 947df = 2177 p lt 00001) The lowest defoliation was obtained with non-Bt soybean plus Fortenzareg

(057 plusmn 012) whereas the control plants showed the highest defoliationA comparison of the potential risk of these species on untreated plants (non-Bt soybean without

seed treatment) showed significant differences (F = 1009 df = 4293 p lt 00001) The highest defoliation

Insects 2018 9 93 7 of 13

damage was produced by S eridania larvae (393 plusmn 189) followed by S albula (102 plusmn 097) S cosmiodes(91 plusmn 079) S frugiperda (67 plusmn 054) and H gelotopoeon (48 plusmn 043)Insects 2018 9 x FOR PEER REVIEW 7 of 13

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albula Spodoptera

cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae in different

soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Bt soybean

without seed treatment) Means plusmn SE within species accompanied by different letters indicate

significant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac against H

gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performance with that

of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On the other hand the

performance analysis made among the species using non-Bt soybean without seed treatment

showed which of these species would represent a potential risk for soybean crops For both analyses

the defoliation and potential risk were calculated considering the identity for each species in

greenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This

new technology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S

albula

Non-Bt soybean with seed treatment provided good control of the five species Nevertheless

this control will be only for the early plant growth stage when plants have more insecticide active

ingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in the

lowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and the

differences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and Argentina A

study of diversity composition and population dynamics of arthropods in non-Bt soybean and Bt

soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantly

controlled by Bt soybean However other species of the Spodoptera complex were not controlled by

this technology [70] Other studies reported that S cosmiodes was the most abundant species

attacking Bt soybean [71] and that development and reproduction of this species were not affected

by the Cry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the

soybean cycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the

population abundance of the last two species was similar in Bt and non-Bt soybean In northwestern

Argentina a trial conducted to evaluate Bt soybean against different insect pest and natural

predators found that this new technology provided good control of target pests such as A

gemmatalis C includens and R nu The levels of leaf damage observed with Bt soybean were lowest

and significantly different to those obtained with non-Bt soybean [4] On the other hand bioassays

and greenhouse studies found that S cosmiodes S eridania and S frugiperda exhibited low to no

susceptibility to MON 87701 times MON 89788 soybean containing the protein Cry1Ac and these species

showed higher tolerance to the Cry1Ac protein than other Lepidoptera species such as C includens

a a

b

b

ba a aa

a

b

b c

c

c

0

5

10

15

20

25

30

35

40

45

H gelotopoeon S albula S cosmiodes S eridania S frugiperda

Me

an

(plusmn

SE

) p

erc

en

tag

e o

f d

efo

lia

tio

n

T1 T2 T3

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albulaSpodoptera cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae indifferent soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Btsoybean without seed treatment) Means plusmn SE within species accompanied by different letters indicatesignificant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac againstH gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performancewith that of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On theother hand the performance analysis made among the species using non-Bt soybean without seedtreatment showed which of these species would represent a potential risk for soybean crops For bothanalyses the defoliation and potential risk were calculated considering the identity for each species ingreenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This newtechnology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S albula

Non-Bt soybean with seed treatment provided good control of the five species Neverthelessthis control will be only for the early plant growth stage when plants have more insecticide activeingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in thelowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and thedifferences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and ArgentinaA study of diversity composition and population dynamics of arthropods in non-Bt soybean andBt soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantlycontrolled by Bt soybean However other species of the Spodoptera complex were not controlled bythis technology [70] Other studies reported that S cosmiodes was the most abundant species attackingBt soybean [71] and that development and reproduction of this species were not affected by theCry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the soybeancycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the populationabundance of the last two species was similar in Bt and non-Bt soybean In northwestern Argentinaa trial conducted to evaluate Bt soybean against different insect pest and natural predators foundthat this new technology provided good control of target pests such as A gemmatalis C includens

Insects 2018 9 93 8 of 13

and R nu The levels of leaf damage observed with Bt soybean were lowest and significantly differentto those obtained with non-Bt soybean [4] On the other hand bioassays and greenhouse studiesfound that S cosmiodes S eridania and S frugiperda exhibited low to no susceptibility to MON 87701 timesMON 89788 soybean containing the protein Cry1Ac and these species showed higher tolerance tothe Cry1Ac protein than other Lepidoptera species such as C includens C virescens and H zea [60]In the same study a moderate larval incidence of S eridania and S frugiperda on MON 87701 x MON89788 soybean and the respective near-isogenic negative check was found No significant differencesin larval incidence and defoliation by S eridania were found with Bt soybean and the near-isogenicnegative checks for both maturity groups Similarly larval incidence of S frugiperda on Bt soybeandid not differ significantly from the respective near-isogenic negative checks for both maturity groupsHowever defoliation by S frugiperda on Bt soybean was significantly lower than on the near-isogenicbeing the defoliation registered similar to those reported in this study in Bt soybean The defoliationrecorded for S eridania was different to those reported in greenhouse studies in Brazil [60] but in bothstudies defoliation was high in non-Bt soybean These differences could be due to the number oflarvae used to evaluate the defoliation per plants

The non-Bt soybean with seed treatment showed the lowest defoliation of S frugiperda S albulaS cosmiodes and S eridania These results are similar to another study [73] where diamides had goodpotential to control different lepidopteran pests such as S eridania S cosmiodes S albula A gemmatalisand S frugiperda

Considering the performance of each species using non-Bt soybean without seed treatmentH gelotopoeon showed the lowest defoliation This species is one of the most important pests insoybean crops but its larvae prefer the reproductive plant growth stages [5074] which explains thelow defoliation recorded in this study As mentioned Spodoptera spp are polyphagous but showpreferences to different host plants such as the preference of S frugiperda to corn (Zea mays L (Poaceae))over soybean and other crops [75] Spodoptera cosmiodes and S albula presented similar levels ofdefoliation in our test although S cosmiodes is the most frequent Spodoptera spp affecting soybeancrops during the vegetative and reproductive stages [5614162050] Another study suggested thatS cosmioides may be more adapted to chemical compounds of soybean and cotton (Gossypium hirsutumL (Malvaceae)) given their faster development and higher survival rates on these hosts [76] Larvaeof S albula feed on a wide variety of host plants and they also exhibit some preference for severalweeds (Boerhavia erecta (L) (Nyctaginaceae) Echinochloa colonum (L) Link (Poaceae) from whichthey can migrate to cultivated plants [2729] The highest defoliation damage was produced byS eridania This species had been cited as infesting a large number of crops in various regions ofthe Americas [497477] Additionally this species has been reported from outbreaks under differentconditions [151828] This species develops on weeds which generally constitute a primary source ofcultivated plant infestations such as those of soybean [152628] Considering the defoliation recordedin this study S eridania would represent a potential risk to soybean crops According to these resultsthis species may be more adapted to chemical compounds of soybean given their faster developmentand higher survival rates [76]

5 Conclusions

Our results suggest that H gelotopoeon S frugiperda and S albula were susceptible to the Cry1Acprotein However S eridania and S cosmiodes were not susceptible to the Cry1Ac protein in MON87701 times MON 89788 soybean when evaluated by greenhouse infestation supporting the idea that thelevel of activity of this protein against these species is low Consequently other control tactics such asseed treatment must be used in combination with MON 87701 times MON 89788 soybean in the field forthe efficient management of Spodoptera species

Our results contribute to determining the defoliation and potential risk of these pests in soybeancrops Considering the increasing importance of S cosmioides and S eridania in the region future studiesshould be focused toward understanding survival population dynamics and infestation of these

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 5 of 13

Helicoverpa gelotopoeon is another major pest of soybean Larvae of this species cause damage inthe vegetative and reproductive plant growth stages In Tucumaacuten and other provinces of Argentinathis species causes severe damage to soybean and chickpea (Cicer arietinum L (Fabaceae)) crops and canbe difficult to control with insecticides [50ndash53] Some other species of Helicoverpa such as H armigeraHuumlbner and H zea have also developed resistance to insecticides and Cry proteins [54ndash59]

Previous studies were conducted under field conditions considering the Helicoverpa genus ingeneral [7819] This has led to much speculation given the coexistence of H gelotopoeon and H armigerain soybean crops in northwestern Argentina [52] In this genus species can only be separated bymorphological characters of the adults [50] Thus the study of H gelotopoeon performance is importantto know the real potential of defoliation in soybean crops

The great potential for defoliation of soybean plants [1620] and damage to flowers and pods [14]by Spodoptera spp and H gelotopoeon [5152] requires the adoption of control tactics to prevent yield lossControl is achieved with insecticides often indirectly as result of sprays for A gemmatalis C includensand R nu [5ndash860]

The rapid adoption of Bt soybean in Argentina [2] and other countries in South America [61] hasincreased the need to know the behavior of nontarget and target pests of Bt soybean The objectiveof this study was to evaluate the performance of soybean expressing Cry1Ac against differentlepidopteran nontarget and target insect pests and to compare its performance with that of a non-Btsoybean with seed treatment We addressed this study by evaluating the defoliation produced bydifferent lepidopteran pests recorded at eight days after infestation

2 Materials and Methods

21 Larval Collection

Larvae of H gelotopoeon S albula S cosmiodes S eridania and S frugiperda were collected fromJanuary to March 2014 in commercial soybean fields in La Cocha (Dpto La Cocha) and Overo Pozo(Dpto Cruz Alta) counties in Tucumaacuten province (Argentina) A minimum of 250 larvae (from 3rd to6th instars) of each species were collected using a vertical beat sheet [62] Then each larva was placedin a glass tube (12 cm H and 15 cm D) with leaves of soybean and transported to our laboratoriesat the Estacioacuten Experimental Agroindustrial Obispo Colombres (EEAOC) The collected larvae wereplaced in growth chambers under controlled conditions (27 plusmn 2 C 70 plusmn 5 RH 1410 h LD) untiladult emergence Late larval instars and adults were examined using morphological characters bothto confirm the identity of species [47496364] and to establish pure cultures for each species in thelaboratory Voucher specimens for each species were deposited in the collection of Seccioacuten ZoologiacuteaAgriacutecola (EEAOC) Tucumaacuten Argentina

22 Insect Rearing

Each species colony was maintained in the same chamber under identically controlled conditionsat 27 plusmn 2 C 70 plusmn 5 RH 1410 h LD Colonies were reared according to the methodologydescribed by Muruacutea et al [65] and Herrero et al [53] Twenty-five pairs per cage and per species(25 females and 25 males) (N = 6) were used Adults were maintained in cylindrical ovipositioncages made out of plastic mesh (20 cm high and 15 cm in diameter) lined with polyethylene bagsas an oviposition substrate For aeration both ends of the cage were covered with a nylon clothThe food was provided via a cotton plug saturated with a mixture of honey and water (11 vv)which was replaced every day Cages were checked daily for oviposition and adult mortality Eggswere collected daily with a moistened brush and deposited in Petri dishes lined with moistenedfilter paper Once emerged neonate larvae were placed in 20-cm diameter 800-mL containerswith an artificial larval diet that included bean flour (Grandietreg Buenos Aires Argentina) wheatgerm (Grandietreg Buenos Aires Argentina) brewerrsquos yeast (Calsareg Tucumaacuten Argentina) vitaminC (Anedrareg Buenos Aires Argentina) sorbic acid (Anedrareg Buenos Aires Argentina) vitamin

Insects 2018 9 93 6 of 13

supplement amino acids (Ruminalreg Buenos Aires Argentina) and methylparaben (Todo DrogaregCoacuterdoba Argentina) Diet was replaced every five days As larvae pupated pupae were sexed andplaced in cup containers with moistened filter paper until adultrsquos emergence Adults were used toinitiate a new generation After establishing a colony for each species individuals from the 2ndgeneration (F2) were used for the evaluation of soybean Cry1Ac against different pest species ina greenhouse

23 Greenhouse Studies

Soybean seeds of maturity group 7 were used (recommended for cultivation in northwesternArgentina) The treatments evaluated were Bt soybean Cry1Ac (T1) non-Bt soybean plus seedtreatment (T2) (Fortenzareg diamide insecticide Syngenta Argentina) according to the doseraterecommended by the company (36 g ai100 Kgseed) and non-Bt soybean without seed treatmentas an untreated control (T3) The three treatments were planted in different pots (15 cm D 600 mL)using sterilized soil One seed per pot was planted and each plant was labeled to distinguish boththe species and treatment The plants were maintained under greenhouse conditions under ambientlighting at approximately 33 plusmn 4 C 80 plusmn 10 RH 1410 h LD

The experimental design was completely randomized with three replicates per treatmentwhere each replicate consisted of 20 soybean plants A total of 60 plants for each pest species (5)per treatment (3) were evaluated resulting in 900 plants

Each plant for each treatment was inoculated at the V1 stage [66] (approximately 14 days afterplanting) with 10 larvae (L1) of a pest species The evaluations of defoliation produced by each specieswere recorded at 8 days after inoculation (DAI) according the visual estimation of defoliation scaledescribed by Kogan and Turnipseed [67]

Expression of the Cry1Ac protein in the soybean plants was confirmed using qualitative ELISAQuickstix lateral flow detection strips (Envirologix Portland ME USA)

24 Data Analysis

To meet parametric assumptions percentage data on defoliation damage were transformed toarcsine square root prior to analysis [68] nevertheless untransformed means (plusmnSE) are shown in thefigure The percentage of defoliation damage produced by each species in the different treatments andthe performance of these species using non-Bt soybean without seed treatment were analyzed using aone-way ANOVA and means were separated using Tukeyrsquos tests (p lt 005) with InfoStat [69]

3 Results

All results are shown in Figure 1 Significant differences were found in the average defoliationdamage produced by H gelotopoeon among different treatments (F = 643 df = 2177 p lt 00001)Bt soybean (T1) and non-Bt soybean plus Fortenzareg (T2) presented similar values but significantdifferences were found when they were compared with the control (T3) The average defoliationdamage produced by S albula was lower in the Bt soybean and non-Bt soybean plus Fortenzareg

treatments compared to the control (Figure 1) (F = 1110 df = 2177 p lt 00001) For S cosmiodes lowerfeeding damage was recorded in the non-Bt soybean plus Fortenzareg treatment compared to the Btsoybean and control plants (F = 760 df = 2176 p lt 00001) The best control of S eridania was with thenon-Bt soybean plus Fortenzareg treatment registering a lower percentage of defoliation compared toBt soybean and the control plants (F = 2691 df = 2177 p lt 00001) Finally significant differences werefound in the percentage of defoliation produced by S frugiperda in the different treatments (F = 947df = 2177 p lt 00001) The lowest defoliation was obtained with non-Bt soybean plus Fortenzareg

(057 plusmn 012) whereas the control plants showed the highest defoliationA comparison of the potential risk of these species on untreated plants (non-Bt soybean without

seed treatment) showed significant differences (F = 1009 df = 4293 p lt 00001) The highest defoliation

Insects 2018 9 93 7 of 13

damage was produced by S eridania larvae (393 plusmn 189) followed by S albula (102 plusmn 097) S cosmiodes(91 plusmn 079) S frugiperda (67 plusmn 054) and H gelotopoeon (48 plusmn 043)Insects 2018 9 x FOR PEER REVIEW 7 of 13

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albula Spodoptera

cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae in different

soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Bt soybean

without seed treatment) Means plusmn SE within species accompanied by different letters indicate

significant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac against H

gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performance with that

of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On the other hand the

performance analysis made among the species using non-Bt soybean without seed treatment

showed which of these species would represent a potential risk for soybean crops For both analyses

the defoliation and potential risk were calculated considering the identity for each species in

greenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This

new technology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S

albula

Non-Bt soybean with seed treatment provided good control of the five species Nevertheless

this control will be only for the early plant growth stage when plants have more insecticide active

ingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in the

lowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and the

differences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and Argentina A

study of diversity composition and population dynamics of arthropods in non-Bt soybean and Bt

soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantly

controlled by Bt soybean However other species of the Spodoptera complex were not controlled by

this technology [70] Other studies reported that S cosmiodes was the most abundant species

attacking Bt soybean [71] and that development and reproduction of this species were not affected

by the Cry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the

soybean cycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the

population abundance of the last two species was similar in Bt and non-Bt soybean In northwestern

Argentina a trial conducted to evaluate Bt soybean against different insect pest and natural

predators found that this new technology provided good control of target pests such as A

gemmatalis C includens and R nu The levels of leaf damage observed with Bt soybean were lowest

and significantly different to those obtained with non-Bt soybean [4] On the other hand bioassays

and greenhouse studies found that S cosmiodes S eridania and S frugiperda exhibited low to no

susceptibility to MON 87701 times MON 89788 soybean containing the protein Cry1Ac and these species

showed higher tolerance to the Cry1Ac protein than other Lepidoptera species such as C includens

a a

b

b

ba a aa

a

b

b c

c

c

0

5

10

15

20

25

30

35

40

45

H gelotopoeon S albula S cosmiodes S eridania S frugiperda

Me

an

(plusmn

SE

) p

erc

en

tag

e o

f d

efo

lia

tio

n

T1 T2 T3

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albulaSpodoptera cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae indifferent soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Btsoybean without seed treatment) Means plusmn SE within species accompanied by different letters indicatesignificant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac againstH gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performancewith that of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On theother hand the performance analysis made among the species using non-Bt soybean without seedtreatment showed which of these species would represent a potential risk for soybean crops For bothanalyses the defoliation and potential risk were calculated considering the identity for each species ingreenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This newtechnology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S albula

Non-Bt soybean with seed treatment provided good control of the five species Neverthelessthis control will be only for the early plant growth stage when plants have more insecticide activeingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in thelowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and thedifferences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and ArgentinaA study of diversity composition and population dynamics of arthropods in non-Bt soybean andBt soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantlycontrolled by Bt soybean However other species of the Spodoptera complex were not controlled bythis technology [70] Other studies reported that S cosmiodes was the most abundant species attackingBt soybean [71] and that development and reproduction of this species were not affected by theCry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the soybeancycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the populationabundance of the last two species was similar in Bt and non-Bt soybean In northwestern Argentinaa trial conducted to evaluate Bt soybean against different insect pest and natural predators foundthat this new technology provided good control of target pests such as A gemmatalis C includens

Insects 2018 9 93 8 of 13

and R nu The levels of leaf damage observed with Bt soybean were lowest and significantly differentto those obtained with non-Bt soybean [4] On the other hand bioassays and greenhouse studiesfound that S cosmiodes S eridania and S frugiperda exhibited low to no susceptibility to MON 87701 timesMON 89788 soybean containing the protein Cry1Ac and these species showed higher tolerance tothe Cry1Ac protein than other Lepidoptera species such as C includens C virescens and H zea [60]In the same study a moderate larval incidence of S eridania and S frugiperda on MON 87701 x MON89788 soybean and the respective near-isogenic negative check was found No significant differencesin larval incidence and defoliation by S eridania were found with Bt soybean and the near-isogenicnegative checks for both maturity groups Similarly larval incidence of S frugiperda on Bt soybeandid not differ significantly from the respective near-isogenic negative checks for both maturity groupsHowever defoliation by S frugiperda on Bt soybean was significantly lower than on the near-isogenicbeing the defoliation registered similar to those reported in this study in Bt soybean The defoliationrecorded for S eridania was different to those reported in greenhouse studies in Brazil [60] but in bothstudies defoliation was high in non-Bt soybean These differences could be due to the number oflarvae used to evaluate the defoliation per plants

The non-Bt soybean with seed treatment showed the lowest defoliation of S frugiperda S albulaS cosmiodes and S eridania These results are similar to another study [73] where diamides had goodpotential to control different lepidopteran pests such as S eridania S cosmiodes S albula A gemmatalisand S frugiperda

Considering the performance of each species using non-Bt soybean without seed treatmentH gelotopoeon showed the lowest defoliation This species is one of the most important pests insoybean crops but its larvae prefer the reproductive plant growth stages [5074] which explains thelow defoliation recorded in this study As mentioned Spodoptera spp are polyphagous but showpreferences to different host plants such as the preference of S frugiperda to corn (Zea mays L (Poaceae))over soybean and other crops [75] Spodoptera cosmiodes and S albula presented similar levels ofdefoliation in our test although S cosmiodes is the most frequent Spodoptera spp affecting soybeancrops during the vegetative and reproductive stages [5614162050] Another study suggested thatS cosmioides may be more adapted to chemical compounds of soybean and cotton (Gossypium hirsutumL (Malvaceae)) given their faster development and higher survival rates on these hosts [76] Larvaeof S albula feed on a wide variety of host plants and they also exhibit some preference for severalweeds (Boerhavia erecta (L) (Nyctaginaceae) Echinochloa colonum (L) Link (Poaceae) from whichthey can migrate to cultivated plants [2729] The highest defoliation damage was produced byS eridania This species had been cited as infesting a large number of crops in various regions ofthe Americas [497477] Additionally this species has been reported from outbreaks under differentconditions [151828] This species develops on weeds which generally constitute a primary source ofcultivated plant infestations such as those of soybean [152628] Considering the defoliation recordedin this study S eridania would represent a potential risk to soybean crops According to these resultsthis species may be more adapted to chemical compounds of soybean given their faster developmentand higher survival rates [76]

5 Conclusions

Our results suggest that H gelotopoeon S frugiperda and S albula were susceptible to the Cry1Acprotein However S eridania and S cosmiodes were not susceptible to the Cry1Ac protein in MON87701 times MON 89788 soybean when evaluated by greenhouse infestation supporting the idea that thelevel of activity of this protein against these species is low Consequently other control tactics such asseed treatment must be used in combination with MON 87701 times MON 89788 soybean in the field forthe efficient management of Spodoptera species

Our results contribute to determining the defoliation and potential risk of these pests in soybeancrops Considering the increasing importance of S cosmioides and S eridania in the region future studiesshould be focused toward understanding survival population dynamics and infestation of these

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 6 of 13

supplement amino acids (Ruminalreg Buenos Aires Argentina) and methylparaben (Todo DrogaregCoacuterdoba Argentina) Diet was replaced every five days As larvae pupated pupae were sexed andplaced in cup containers with moistened filter paper until adultrsquos emergence Adults were used toinitiate a new generation After establishing a colony for each species individuals from the 2ndgeneration (F2) were used for the evaluation of soybean Cry1Ac against different pest species ina greenhouse

23 Greenhouse Studies

Soybean seeds of maturity group 7 were used (recommended for cultivation in northwesternArgentina) The treatments evaluated were Bt soybean Cry1Ac (T1) non-Bt soybean plus seedtreatment (T2) (Fortenzareg diamide insecticide Syngenta Argentina) according to the doseraterecommended by the company (36 g ai100 Kgseed) and non-Bt soybean without seed treatmentas an untreated control (T3) The three treatments were planted in different pots (15 cm D 600 mL)using sterilized soil One seed per pot was planted and each plant was labeled to distinguish boththe species and treatment The plants were maintained under greenhouse conditions under ambientlighting at approximately 33 plusmn 4 C 80 plusmn 10 RH 1410 h LD

The experimental design was completely randomized with three replicates per treatmentwhere each replicate consisted of 20 soybean plants A total of 60 plants for each pest species (5)per treatment (3) were evaluated resulting in 900 plants

Each plant for each treatment was inoculated at the V1 stage [66] (approximately 14 days afterplanting) with 10 larvae (L1) of a pest species The evaluations of defoliation produced by each specieswere recorded at 8 days after inoculation (DAI) according the visual estimation of defoliation scaledescribed by Kogan and Turnipseed [67]

Expression of the Cry1Ac protein in the soybean plants was confirmed using qualitative ELISAQuickstix lateral flow detection strips (Envirologix Portland ME USA)

24 Data Analysis

To meet parametric assumptions percentage data on defoliation damage were transformed toarcsine square root prior to analysis [68] nevertheless untransformed means (plusmnSE) are shown in thefigure The percentage of defoliation damage produced by each species in the different treatments andthe performance of these species using non-Bt soybean without seed treatment were analyzed using aone-way ANOVA and means were separated using Tukeyrsquos tests (p lt 005) with InfoStat [69]

3 Results

All results are shown in Figure 1 Significant differences were found in the average defoliationdamage produced by H gelotopoeon among different treatments (F = 643 df = 2177 p lt 00001)Bt soybean (T1) and non-Bt soybean plus Fortenzareg (T2) presented similar values but significantdifferences were found when they were compared with the control (T3) The average defoliationdamage produced by S albula was lower in the Bt soybean and non-Bt soybean plus Fortenzareg

treatments compared to the control (Figure 1) (F = 1110 df = 2177 p lt 00001) For S cosmiodes lowerfeeding damage was recorded in the non-Bt soybean plus Fortenzareg treatment compared to the Btsoybean and control plants (F = 760 df = 2176 p lt 00001) The best control of S eridania was with thenon-Bt soybean plus Fortenzareg treatment registering a lower percentage of defoliation compared toBt soybean and the control plants (F = 2691 df = 2177 p lt 00001) Finally significant differences werefound in the percentage of defoliation produced by S frugiperda in the different treatments (F = 947df = 2177 p lt 00001) The lowest defoliation was obtained with non-Bt soybean plus Fortenzareg

(057 plusmn 012) whereas the control plants showed the highest defoliationA comparison of the potential risk of these species on untreated plants (non-Bt soybean without

seed treatment) showed significant differences (F = 1009 df = 4293 p lt 00001) The highest defoliation

Insects 2018 9 93 7 of 13

damage was produced by S eridania larvae (393 plusmn 189) followed by S albula (102 plusmn 097) S cosmiodes(91 plusmn 079) S frugiperda (67 plusmn 054) and H gelotopoeon (48 plusmn 043)Insects 2018 9 x FOR PEER REVIEW 7 of 13

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albula Spodoptera

cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae in different

soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Bt soybean

without seed treatment) Means plusmn SE within species accompanied by different letters indicate

significant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac against H

gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performance with that

of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On the other hand the

performance analysis made among the species using non-Bt soybean without seed treatment

showed which of these species would represent a potential risk for soybean crops For both analyses

the defoliation and potential risk were calculated considering the identity for each species in

greenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This

new technology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S

albula

Non-Bt soybean with seed treatment provided good control of the five species Nevertheless

this control will be only for the early plant growth stage when plants have more insecticide active

ingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in the

lowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and the

differences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and Argentina A

study of diversity composition and population dynamics of arthropods in non-Bt soybean and Bt

soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantly

controlled by Bt soybean However other species of the Spodoptera complex were not controlled by

this technology [70] Other studies reported that S cosmiodes was the most abundant species

attacking Bt soybean [71] and that development and reproduction of this species were not affected

by the Cry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the

soybean cycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the

population abundance of the last two species was similar in Bt and non-Bt soybean In northwestern

Argentina a trial conducted to evaluate Bt soybean against different insect pest and natural

predators found that this new technology provided good control of target pests such as A

gemmatalis C includens and R nu The levels of leaf damage observed with Bt soybean were lowest

and significantly different to those obtained with non-Bt soybean [4] On the other hand bioassays

and greenhouse studies found that S cosmiodes S eridania and S frugiperda exhibited low to no

susceptibility to MON 87701 times MON 89788 soybean containing the protein Cry1Ac and these species

showed higher tolerance to the Cry1Ac protein than other Lepidoptera species such as C includens

a a

b

b

ba a aa

a

b

b c

c

c

0

5

10

15

20

25

30

35

40

45

H gelotopoeon S albula S cosmiodes S eridania S frugiperda

Me

an

(plusmn

SE

) p

erc

en

tag

e o

f d

efo

lia

tio

n

T1 T2 T3

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albulaSpodoptera cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae indifferent soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Btsoybean without seed treatment) Means plusmn SE within species accompanied by different letters indicatesignificant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac againstH gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performancewith that of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On theother hand the performance analysis made among the species using non-Bt soybean without seedtreatment showed which of these species would represent a potential risk for soybean crops For bothanalyses the defoliation and potential risk were calculated considering the identity for each species ingreenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This newtechnology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S albula

Non-Bt soybean with seed treatment provided good control of the five species Neverthelessthis control will be only for the early plant growth stage when plants have more insecticide activeingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in thelowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and thedifferences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and ArgentinaA study of diversity composition and population dynamics of arthropods in non-Bt soybean andBt soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantlycontrolled by Bt soybean However other species of the Spodoptera complex were not controlled bythis technology [70] Other studies reported that S cosmiodes was the most abundant species attackingBt soybean [71] and that development and reproduction of this species were not affected by theCry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the soybeancycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the populationabundance of the last two species was similar in Bt and non-Bt soybean In northwestern Argentinaa trial conducted to evaluate Bt soybean against different insect pest and natural predators foundthat this new technology provided good control of target pests such as A gemmatalis C includens

Insects 2018 9 93 8 of 13

and R nu The levels of leaf damage observed with Bt soybean were lowest and significantly differentto those obtained with non-Bt soybean [4] On the other hand bioassays and greenhouse studiesfound that S cosmiodes S eridania and S frugiperda exhibited low to no susceptibility to MON 87701 timesMON 89788 soybean containing the protein Cry1Ac and these species showed higher tolerance tothe Cry1Ac protein than other Lepidoptera species such as C includens C virescens and H zea [60]In the same study a moderate larval incidence of S eridania and S frugiperda on MON 87701 x MON89788 soybean and the respective near-isogenic negative check was found No significant differencesin larval incidence and defoliation by S eridania were found with Bt soybean and the near-isogenicnegative checks for both maturity groups Similarly larval incidence of S frugiperda on Bt soybeandid not differ significantly from the respective near-isogenic negative checks for both maturity groupsHowever defoliation by S frugiperda on Bt soybean was significantly lower than on the near-isogenicbeing the defoliation registered similar to those reported in this study in Bt soybean The defoliationrecorded for S eridania was different to those reported in greenhouse studies in Brazil [60] but in bothstudies defoliation was high in non-Bt soybean These differences could be due to the number oflarvae used to evaluate the defoliation per plants

The non-Bt soybean with seed treatment showed the lowest defoliation of S frugiperda S albulaS cosmiodes and S eridania These results are similar to another study [73] where diamides had goodpotential to control different lepidopteran pests such as S eridania S cosmiodes S albula A gemmatalisand S frugiperda

Considering the performance of each species using non-Bt soybean without seed treatmentH gelotopoeon showed the lowest defoliation This species is one of the most important pests insoybean crops but its larvae prefer the reproductive plant growth stages [5074] which explains thelow defoliation recorded in this study As mentioned Spodoptera spp are polyphagous but showpreferences to different host plants such as the preference of S frugiperda to corn (Zea mays L (Poaceae))over soybean and other crops [75] Spodoptera cosmiodes and S albula presented similar levels ofdefoliation in our test although S cosmiodes is the most frequent Spodoptera spp affecting soybeancrops during the vegetative and reproductive stages [5614162050] Another study suggested thatS cosmioides may be more adapted to chemical compounds of soybean and cotton (Gossypium hirsutumL (Malvaceae)) given their faster development and higher survival rates on these hosts [76] Larvaeof S albula feed on a wide variety of host plants and they also exhibit some preference for severalweeds (Boerhavia erecta (L) (Nyctaginaceae) Echinochloa colonum (L) Link (Poaceae) from whichthey can migrate to cultivated plants [2729] The highest defoliation damage was produced byS eridania This species had been cited as infesting a large number of crops in various regions ofthe Americas [497477] Additionally this species has been reported from outbreaks under differentconditions [151828] This species develops on weeds which generally constitute a primary source ofcultivated plant infestations such as those of soybean [152628] Considering the defoliation recordedin this study S eridania would represent a potential risk to soybean crops According to these resultsthis species may be more adapted to chemical compounds of soybean given their faster developmentand higher survival rates [76]

5 Conclusions

Our results suggest that H gelotopoeon S frugiperda and S albula were susceptible to the Cry1Acprotein However S eridania and S cosmiodes were not susceptible to the Cry1Ac protein in MON87701 times MON 89788 soybean when evaluated by greenhouse infestation supporting the idea that thelevel of activity of this protein against these species is low Consequently other control tactics such asseed treatment must be used in combination with MON 87701 times MON 89788 soybean in the field forthe efficient management of Spodoptera species

Our results contribute to determining the defoliation and potential risk of these pests in soybeancrops Considering the increasing importance of S cosmioides and S eridania in the region future studiesshould be focused toward understanding survival population dynamics and infestation of these

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 7 of 13

damage was produced by S eridania larvae (393 plusmn 189) followed by S albula (102 plusmn 097) S cosmiodes(91 plusmn 079) S frugiperda (67 plusmn 054) and H gelotopoeon (48 plusmn 043)Insects 2018 9 x FOR PEER REVIEW 7 of 13

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albula Spodoptera

cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae in different

soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Bt soybean

without seed treatment) Means plusmn SE within species accompanied by different letters indicate

significant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac against H

gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performance with that

of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On the other hand the

performance analysis made among the species using non-Bt soybean without seed treatment

showed which of these species would represent a potential risk for soybean crops For both analyses

the defoliation and potential risk were calculated considering the identity for each species in

greenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This

new technology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S

albula

Non-Bt soybean with seed treatment provided good control of the five species Nevertheless

this control will be only for the early plant growth stage when plants have more insecticide active

ingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in the

lowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and the

differences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and Argentina A

study of diversity composition and population dynamics of arthropods in non-Bt soybean and Bt

soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantly

controlled by Bt soybean However other species of the Spodoptera complex were not controlled by

this technology [70] Other studies reported that S cosmiodes was the most abundant species

attacking Bt soybean [71] and that development and reproduction of this species were not affected

by the Cry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the

soybean cycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the

population abundance of the last two species was similar in Bt and non-Bt soybean In northwestern

Argentina a trial conducted to evaluate Bt soybean against different insect pest and natural

predators found that this new technology provided good control of target pests such as A

gemmatalis C includens and R nu The levels of leaf damage observed with Bt soybean were lowest

and significantly different to those obtained with non-Bt soybean [4] On the other hand bioassays

and greenhouse studies found that S cosmiodes S eridania and S frugiperda exhibited low to no

susceptibility to MON 87701 times MON 89788 soybean containing the protein Cry1Ac and these species

showed higher tolerance to the Cry1Ac protein than other Lepidoptera species such as C includens

a a

b

b

ba a aa

a

b

b c

c

c

0

5

10

15

20

25

30

35

40

45

H gelotopoeon S albula S cosmiodes S eridania S frugiperda

Me

an

(plusmn

SE

) p

erc

en

tag

e o

f d

efo

lia

tio

n

T1 T2 T3

Figure 1 Percentage of defoliation produced by Helicoverpa gelotopoeon Spodoptera albulaSpodoptera cosmiodes Spodoptera eridania and Spodoptera frugiperda (Lepidoptera Noctuidae) larvae indifferent soybean treatments (T1 Bt soybean T2 non-Bt soybean with seed treatment T3 non-Btsoybean without seed treatment) Means plusmn SE within species accompanied by different letters indicatesignificant differences (Tukey test p lt 005)

4 Discussion

This study was conducted to characterize the efficacy of soybean expressing Cry1Ac againstH gelotopoeon S albula S cosmiodes S eridania and S frugiperda and compare its performancewith that of a non-Bt soybean with seed treatment by assessing defoliation (Figure 1) On theother hand the performance analysis made among the species using non-Bt soybean without seedtreatment showed which of these species would represent a potential risk for soybean crops For bothanalyses the defoliation and potential risk were calculated considering the identity for each species ingreenhouse conditions (Table 1)

Our results showed that Bt soybean provided variable control of some pests evaluated This newtechnology had the best control of H gelotopoeon and a suppressive effect on S frugiperda and S albula

Non-Bt soybean with seed treatment provided good control of the five species Neverthelessthis control will be only for the early plant growth stage when plants have more insecticide activeingredient in their system S cosmiodes S eridania S frugiperda and S albula feeding resulted in thelowest percentage of defoliation compared with the other treatments

In the case of S albula the defoliation recorded in T1 was similar to that recorded in T2 and thedifferences were not significant

These results are consistent with field studies evaluating Bt soybean in Brazil and ArgentinaA study of diversity composition and population dynamics of arthropods in non-Bt soybean andBt soybean showed that A gemmatalis C includens C virescens and S frugiperda were significantlycontrolled by Bt soybean However other species of the Spodoptera complex were not controlled bythis technology [70] Other studies reported that S cosmiodes was the most abundant species attackingBt soybean [71] and that development and reproduction of this species were not affected by theCry1Ac protein [20] A field study showed that the lepidopteran pests recorded during the soybeancycle were R nu A gemmatalis H gelotopoeon S frugiperda and S cosmioides [72] and the populationabundance of the last two species was similar in Bt and non-Bt soybean In northwestern Argentinaa trial conducted to evaluate Bt soybean against different insect pest and natural predators foundthat this new technology provided good control of target pests such as A gemmatalis C includens

Insects 2018 9 93 8 of 13

and R nu The levels of leaf damage observed with Bt soybean were lowest and significantly differentto those obtained with non-Bt soybean [4] On the other hand bioassays and greenhouse studiesfound that S cosmiodes S eridania and S frugiperda exhibited low to no susceptibility to MON 87701 timesMON 89788 soybean containing the protein Cry1Ac and these species showed higher tolerance tothe Cry1Ac protein than other Lepidoptera species such as C includens C virescens and H zea [60]In the same study a moderate larval incidence of S eridania and S frugiperda on MON 87701 x MON89788 soybean and the respective near-isogenic negative check was found No significant differencesin larval incidence and defoliation by S eridania were found with Bt soybean and the near-isogenicnegative checks for both maturity groups Similarly larval incidence of S frugiperda on Bt soybeandid not differ significantly from the respective near-isogenic negative checks for both maturity groupsHowever defoliation by S frugiperda on Bt soybean was significantly lower than on the near-isogenicbeing the defoliation registered similar to those reported in this study in Bt soybean The defoliationrecorded for S eridania was different to those reported in greenhouse studies in Brazil [60] but in bothstudies defoliation was high in non-Bt soybean These differences could be due to the number oflarvae used to evaluate the defoliation per plants

The non-Bt soybean with seed treatment showed the lowest defoliation of S frugiperda S albulaS cosmiodes and S eridania These results are similar to another study [73] where diamides had goodpotential to control different lepidopteran pests such as S eridania S cosmiodes S albula A gemmatalisand S frugiperda

Considering the performance of each species using non-Bt soybean without seed treatmentH gelotopoeon showed the lowest defoliation This species is one of the most important pests insoybean crops but its larvae prefer the reproductive plant growth stages [5074] which explains thelow defoliation recorded in this study As mentioned Spodoptera spp are polyphagous but showpreferences to different host plants such as the preference of S frugiperda to corn (Zea mays L (Poaceae))over soybean and other crops [75] Spodoptera cosmiodes and S albula presented similar levels ofdefoliation in our test although S cosmiodes is the most frequent Spodoptera spp affecting soybeancrops during the vegetative and reproductive stages [5614162050] Another study suggested thatS cosmioides may be more adapted to chemical compounds of soybean and cotton (Gossypium hirsutumL (Malvaceae)) given their faster development and higher survival rates on these hosts [76] Larvaeof S albula feed on a wide variety of host plants and they also exhibit some preference for severalweeds (Boerhavia erecta (L) (Nyctaginaceae) Echinochloa colonum (L) Link (Poaceae) from whichthey can migrate to cultivated plants [2729] The highest defoliation damage was produced byS eridania This species had been cited as infesting a large number of crops in various regions ofthe Americas [497477] Additionally this species has been reported from outbreaks under differentconditions [151828] This species develops on weeds which generally constitute a primary source ofcultivated plant infestations such as those of soybean [152628] Considering the defoliation recordedin this study S eridania would represent a potential risk to soybean crops According to these resultsthis species may be more adapted to chemical compounds of soybean given their faster developmentand higher survival rates [76]

5 Conclusions

Our results suggest that H gelotopoeon S frugiperda and S albula were susceptible to the Cry1Acprotein However S eridania and S cosmiodes were not susceptible to the Cry1Ac protein in MON87701 times MON 89788 soybean when evaluated by greenhouse infestation supporting the idea that thelevel of activity of this protein against these species is low Consequently other control tactics such asseed treatment must be used in combination with MON 87701 times MON 89788 soybean in the field forthe efficient management of Spodoptera species

Our results contribute to determining the defoliation and potential risk of these pests in soybeancrops Considering the increasing importance of S cosmioides and S eridania in the region future studiesshould be focused toward understanding survival population dynamics and infestation of these

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 8 of 13

and R nu The levels of leaf damage observed with Bt soybean were lowest and significantly differentto those obtained with non-Bt soybean [4] On the other hand bioassays and greenhouse studiesfound that S cosmiodes S eridania and S frugiperda exhibited low to no susceptibility to MON 87701 timesMON 89788 soybean containing the protein Cry1Ac and these species showed higher tolerance tothe Cry1Ac protein than other Lepidoptera species such as C includens C virescens and H zea [60]In the same study a moderate larval incidence of S eridania and S frugiperda on MON 87701 x MON89788 soybean and the respective near-isogenic negative check was found No significant differencesin larval incidence and defoliation by S eridania were found with Bt soybean and the near-isogenicnegative checks for both maturity groups Similarly larval incidence of S frugiperda on Bt soybeandid not differ significantly from the respective near-isogenic negative checks for both maturity groupsHowever defoliation by S frugiperda on Bt soybean was significantly lower than on the near-isogenicbeing the defoliation registered similar to those reported in this study in Bt soybean The defoliationrecorded for S eridania was different to those reported in greenhouse studies in Brazil [60] but in bothstudies defoliation was high in non-Bt soybean These differences could be due to the number oflarvae used to evaluate the defoliation per plants

The non-Bt soybean with seed treatment showed the lowest defoliation of S frugiperda S albulaS cosmiodes and S eridania These results are similar to another study [73] where diamides had goodpotential to control different lepidopteran pests such as S eridania S cosmiodes S albula A gemmatalisand S frugiperda

Considering the performance of each species using non-Bt soybean without seed treatmentH gelotopoeon showed the lowest defoliation This species is one of the most important pests insoybean crops but its larvae prefer the reproductive plant growth stages [5074] which explains thelow defoliation recorded in this study As mentioned Spodoptera spp are polyphagous but showpreferences to different host plants such as the preference of S frugiperda to corn (Zea mays L (Poaceae))over soybean and other crops [75] Spodoptera cosmiodes and S albula presented similar levels ofdefoliation in our test although S cosmiodes is the most frequent Spodoptera spp affecting soybeancrops during the vegetative and reproductive stages [5614162050] Another study suggested thatS cosmioides may be more adapted to chemical compounds of soybean and cotton (Gossypium hirsutumL (Malvaceae)) given their faster development and higher survival rates on these hosts [76] Larvaeof S albula feed on a wide variety of host plants and they also exhibit some preference for severalweeds (Boerhavia erecta (L) (Nyctaginaceae) Echinochloa colonum (L) Link (Poaceae) from whichthey can migrate to cultivated plants [2729] The highest defoliation damage was produced byS eridania This species had been cited as infesting a large number of crops in various regions ofthe Americas [497477] Additionally this species has been reported from outbreaks under differentconditions [151828] This species develops on weeds which generally constitute a primary source ofcultivated plant infestations such as those of soybean [152628] Considering the defoliation recordedin this study S eridania would represent a potential risk to soybean crops According to these resultsthis species may be more adapted to chemical compounds of soybean given their faster developmentand higher survival rates [76]

5 Conclusions

Our results suggest that H gelotopoeon S frugiperda and S albula were susceptible to the Cry1Acprotein However S eridania and S cosmiodes were not susceptible to the Cry1Ac protein in MON87701 times MON 89788 soybean when evaluated by greenhouse infestation supporting the idea that thelevel of activity of this protein against these species is low Consequently other control tactics such asseed treatment must be used in combination with MON 87701 times MON 89788 soybean in the field forthe efficient management of Spodoptera species

Our results contribute to determining the defoliation and potential risk of these pests in soybeancrops Considering the increasing importance of S cosmioides and S eridania in the region future studiesshould be focused toward understanding survival population dynamics and infestation of these

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 9 of 13

species during all growth stages of soybean plants and their biology including host adaptation On theother hand determination of the combined action of Bt with the seed treatment in the defoliationin the field will be important like other control tactics Therefore the use of Bt soybean as a tool forintegrated pest management should be planned according to the major insect problems in each area

Author Contributions MGM and MAV conceived and designed the experiment MGM and MAVperformed the experiments MGM analyzed the data MIH SVF AM and MGM contributedreagentsmaterialsanalysis tools MGM and AM wrote the paper

Funding This research was funded by [Agencia Nacional de Promocioacuten Cientiacutefica de Argentina through theFondo Nacional de Ciencia y Tecnologiacutea Ministerio de Ciencia Tecnologiacutea e Innovacioacuten Productiva] grant number[PICTO 2016 EEAOC N0112 Preacutestamo BID]

Acknowledgments We thank David Gonzaacutelez and Joseacute Olmos at Estacioacuten Experimental Agroindustrial ObispoColombres for their assistance in the collection of material and excellent technical support in the greenhouse andlaboratory Lic Eduardo Willink (Estacioacuten Experimental Agroindustrial Obispo Colombres) for his constructivecomments on an earlier draft of the manuscript and Fernando Navarro (Consejo Nacional de InvestigacionesCientiacuteficas y Teacutecnicas Instituto Superior de Entomologiacutea Abraham Willink Facultad de Ciencias NaturalesUniversidad Nacional de Tucumaacuten) for the taxonomic identification of the Spodoptera complex and H gelotopoeonfor his unconditional support and for sharing memorable moments This study was supported by the AgenciaNacional de Promocioacuten Cientiacutefica de Argentina through the Fondo Nacional de Ciencia y Tecnologiacutea Ministeriode Ciencia Tecnologiacutea e Innovacioacuten Productiva Grant PICTO 2016 EEAOC N0112 Preacutestamo BID awarded toMGM and Consejo de Investigaciones de la Universidad Nacional de Tucumaacuten Grant CIUNT G6381

Conflicts of Interest The authors declare no conflict of interest

References

1 Silva GV Pasini A Bueno ADF Bortolotto OC Caselato Barbosa G Stopa Cruz YK No impact ofBt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera Pentatomidae)and its egg parasitoid Telenomus podisi (Hymenoptera Platygastridae) Rev Bras Entomol 2014 58 285ndash290[CrossRef]

2 Argenbio Graacutefico de Evolucioacuten de las Superficies Sembradas con OGM en la Argentina en PorcentajesAvailable online httpwwwargenbioorgadcuploadsimagenes_docplanta_stransgenicas1_Grafico_de_evolucion_de_superficie_cultivada_OGM_en_Arg_en_porcentajepdf (accessed on 22 May 2018)

3 Bolsa de Cereales Panorama Agriacutecola Semanal Estimaciones Agriacutecolas Relevamiento al 29032018Available online httpwwwbolsadecerealescomar (accessed on 22 May 2018)

4 Cazado LE Muruacutea MG Casmuz AS Sociacuteas MG Vera MT OacuteBrien CW Gastaminza GGeographical distribution and new associations of Rhyssomatus subtilis (Coleoptera Curculionidae) inArgentina Fla Entomol 2013 96 663ndash669 [CrossRef]

5 Casmuz AS Cazado LE Scalora FS Tuzza MF Fernaacutendez RA Fadda C Fadda LA Dami LColledani Toranzo A Goacutemez CH et al Evaluacioacuten de diferentes alternativas para el control del complejode plagas del cultivo de soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2013ndash2014 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50 EEAOC San Miguel de TucumaacutenArgentina 2014 pp 137ndash142 Available online httpwwweeaocorgarpublicacionescategoria1646110Plagashtml (accessed on 22 May 2018)

6 Casmuz AS Cazado LE Fadda LA Tuzza MF Fadda C Jadur A Merlini A Orce JD Vera AMariacuten MN et al Momento de aplicacioacuten de los insecticidas y su relacioacuten con el control ejercido sobre elcomplejo de orugas defoliadoras de la soja In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2014ndash2015Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 51 EEAOC San Miguelde Tucumaacuten Argentina 2015 pp 120ndash125 Available online httpwwweeaocorgarpublicacionescategoria1653962-Zoologia-621Defoliadorashtml (accessed on 22 May 2018)

7 Casmuz AS Fadda LA Tuzza MF Jadur A Fernaacutendez C Diacuteaz Arnijas G Vera MA Cazado LEOrce JD Muruacutea MG et al Manejo de plagas en soja Intacta y RR1 In El Cultivo de la Soja en elNoroeste Argentino Campantildea 2015ndash2016 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten EspecialSoja EEAOC Nordm 52 EEAOC San Miguel de Tucumaacuten Argentina 2016 pp 134ndash142 Available onlinehttpwwweeaocorgarpublicacionescategoria16645Capitulo-5html (accessed on 22 May 2018)

Insects 2018 9 93 10 of 13

8 Casmuz A Fadda L Vera MA Jadur A Diacuteaz Arnijas G Ramos L Tarulli L Bayos N FernaacutendezAlvarez C Muruacutea MG et al Estrategias para la prevencioacuten de la resistencia de insectos en soja Bt Manejode plagas en el refugio In El Cultivo de la Soja en el Noroeste Argentino Campantildea 2016ndash2017 Devani MRLedesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 53 EEAOC San Miguel de TucumaacutenArgentina 2017 pp 115ndash121 Available online httpwwweeaocorgarpublicacionescategoria16738Capitulo-5---2017html (accessed on 22 May 2018)

9 Wu K Um W Liang G Gou Y Regional reversion of insecticide resistance in Helicoverpa armigera(Lepidoptera Noctuidae) is associated with the use of Bt cotton in northern China Pest Manag Sci 2005 61491ndash498 [CrossRef] [PubMed]

10 Cazado LE Casmuz AS Riley DG Scalora FS Gastaminza GA Muruacutea MG Rhyssomatus subtilis(Coleoptera Curculionidae) impact in soybean plan stands J Entomol Sci 2016 51 69ndash78 [CrossRef]

11 Monsanto Available online httpwwwintactarr2procomar (accessed on 23 May 2018)12 Lu Y Wu K Jiang Y Xia B Li P Feng H Wyckhuys KAG Guo Y Mirid bug outbreaks in multiple

crops correlated with wide-scale adoption of Bt cotton in China Science 2010 328 1151ndash1154 [CrossRef][PubMed]

13 Catangui MA Berg RK Western bean cutworm Striacosta albicosta (Smith) (Lepidoptera Noctuidae) as apotential pest of transgenic Cry1Ab Bacillus thuringiensis corn hybrids in South Dakota Environ Entomol2006 35 1439ndash1452 [CrossRef]

14 Hoffmann-Campo CB Moscardi F Correcirca-Ferreira B Oliveira LJ Sosa-Goacutemez DR Panizzi ARCorso IC Gazzoni DL Oliveira EB Pragas da Soja no Brasil e seu Manejo Integrado Circular TeacutecnicaEmbrapa e Centro Nacional de Pesquisa de Soja Londrina Brazil 2000 Volume 30 p 70 ISSN 1516-7860

15 Santos KB Meneguim AM Neves PMOJ Biology and consumption of Spodoptera eridania (Cramer)(Lepidoptera Noctuidae) in different hosts Neotrop Entomol 2005 4 903ndash910 [CrossRef]

16 Bueno RCOF Bueno AF Moscardi F Parra JRP Hoffmann-Campo CB Lepidopteran larvaconsumption of soybean foliage Basis for developing multiple-species economic thresholds for pestmanagement decisions Pest Manag Sci 2011 67 170ndash174 [CrossRef] [PubMed]

17 Sosa-Goacutemez DR Correa-Ferreira BS Hoffmann-Campo CB Corso IC Oliveira LJ Moscardi FPanizzi AR de Freitas Bueno A Hirose E Roggia S Manual de Identificaccedilatildeo de Insetos e Outros Invertebradosda Cultura de Soja Embrapa Soja Londrina Brazil 2014 p 100 ISSN 1516-781X

18 Favetti BM Butnariu AR Foerster LA Biology and reproductive capacity of Spodoptera eridania (Cramer)(Lepidoptera Noctuidae) in different soybean cultivars Rev Bras Entomol 2015 59 89ndash95 [CrossRef]

19 Cazado LE Casmuz AS Scalora FS Fadda C Fernaacutendez RA Tuzza MF Fadda LA Dami LColledani Toranzo A Jadur A et al Comportamiento de la soja Bt frente a las principales plagasinsectiles y depredadores en el Noroeste Argentino (NOA) In El Cultivo de la Soja en el Noroeste ArgentinoCampantildea 2013ndash2014 Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial Soja EEAOC Nordm 50EEAOC San Miguel de Tucumaacuten Argentina 2014 pp 153ndash161 Available online httpwwweeaocorgarpublicacionescategoria1646312Plagas-vs-Bthtml (accessed on 22 May 2018)

20 Silva VG Bueno FA Bortolottoa CO Santos CA Fernandes PA Biological characteristics of blackarmyworm Spodoptera cosmioides on genetically modified soybean and corn crops that express insecticideCry proteins Rev Bras Entomol 2016 60 255ndash259 [CrossRef]

21 Bentancourt CM Scatoni IB Lepidoacutepteros de importancia econoacutemica In Reconocimiento Biologiacutea y Dantildeosde las Plagas Agriacutecolas y Forestales Hemisferio Sur Montevideo Uruguay 1996 p 129 ISBN 9974-556-96-6

22 Casmuz A Juaacuterez ML Sociacuteas MG Muruacutea MG Prieto S Medina S Willink E Gastaminza GRevisioacuten de los hospederos del gusano cogollero del maiacutez Spodoptera frugiperda (Lepidoptera Noctuidae)Rev Soc Entomol Argent 2010 69 209ndash231

23 Nagoshi RN Meagher RL Behavior and distribution of the two fall armyworm host strains in FloridaFla Entomol 2004 87 440ndash449 [CrossRef]

24 Muruacutea MG Vera MT Abraham S Juareacutez ML Prieto S Head GP Willink E Fitness and matingcompatibility of Spodoptera frugiperda (Smith) (Lepidoptera Noctuidae) populations from different host plantspecies and regions in Argentina Entomol Soc Am 2008 101 639ndash649 [CrossRef]

25 Nagoshi RN Muruacutea MG Hay-Roe M Juaacuterez ML Willink E Meagher RL Genetic characterizationof fall armyworm (Lepidoptera Noctuidae) host strains in Argentina J Econ Entomol 2012 105 418ndash428[CrossRef] [PubMed]

Insects 2018 9 93 11 of 13

26 Montezano DG Specht A Sosa-Goacutemez DR Roque-Specht VF Barros NM Biotic potential andreproductive parameters of Spodoptera eridania (Stoll) (Lepidoptera Noctuidae) in the laboratory Rev BrasEntomol 2013 57 340ndash345 [CrossRef]

27 Montezano DG Specht A Sosa-Goacutemez DR Roque-Specht VF Bortolin TM Fronza E Pezzi PLuz PC Barros NM Immature stages of Spodoptera albula (Walker) (Lepidoptera Noctuidae)Developmental parameters and host plants An Acad Bras Cienc 2013 85 271ndash284 [CrossRef] [PubMed]

28 Montezano DG Specht A Sosa-Goacutemez DR Roque-Specht VF Barros NM Immature stages ofSpodoptera eridania (Lepidoptera Noctuidae) Developmental parameters and host plants J Insect Sci 201414 1ndash11 [CrossRef] [PubMed]

29 Montezano DG Specht A Sosa-Goacutemez DR Roque-Specht VF Bortolin TM Fronza E Pezzi PLuz PC Barros NM Biotic potential fertility and life table of Spodoptera albula (Walker) (LepidopteraNoctuidae) under controlled conditions An Acad Bras Cienc 2014 86 723ndash732 [CrossRef]

30 Specht A Roque-Specht VF Immature stages of Spodoptera cosmiodes (Lepidoptera Noctuidae)Developmental parameters and host plants Zoologia 2016 [CrossRef]

31 Specht A Montezano DG Sosa-Goacutemez DR Paula-Moraes SV Roque-Specht VF Barros NMReproductive potential of Spodoptera eridania (Stoll) (Lepidoptera Noctuidae) in the laboratory Effect ofmultiple couples and the size Braz J Biol 2016 76 526ndash530 [CrossRef] [PubMed]

32 Luttrell RG Wan L Knighten K Variation in susceptibility of Noctuid (Lepidoptera) larvae attackingcotton and soybean to purified endotoxin proteins and commercial formulations of Bacillus thuringiensisJ Econ Entomol 1999 92 21ndash32 [CrossRef]

33 Sivasupramaniam S Moar WJ Ruschke LG Osborn JA Jiang C Sebaugh JL Brown GRShappley ZW Oppenhuizen ME Mullins JW et al Toxicity and characterization of cotton expressingBacillus thuringiensis Cry1Ac and Cry2Ab2 proteins for control of lepidopteran pests J Econ Entomol 2008101 546ndash554 [CrossRef] [PubMed]

34 Yano SAC Santana GKS Neiva MM Moscardi F Martinelli S Sosa Goacutemez DR Toleracircncia deAnticarsia gemmatalis Huumlbner Pseudoplusia includens (Walker) e Rachiplusia nu (Gueneacutee) agrave proteiacutena Cry1AcIn Proceedings of the 6th Congresso Brasileiro de Soja Cuiabaacute Brazil 11ndash14 June 2012 pp 1ndash5

35 Sosa-Goacutemez D Omoto C Resistencia a insecticidas e otros agentes de controle em artroacutepodes asociadosa cultura da soja In Soja Manejo Integrado de Insetos e Outros Artoacutepodes-Praga Hoffmann-Campo CBCorrea-Ferreira BS Moscardi F Eds Embrapa Press Brasilia Brazil 2012 pp 673ndash724ISBN 978-85-7035-139-5

36 Storer NP Babcock JM Schlenz M Meade T Thompson GD Bing JW Huckaba RM Discoveryand characterization of field resistance to Bt maize Spodoptera frugiperda (Lepidoptera Noctuidae) in PuertoRico J Econ Entomol 2010 103 1031ndash1038 [CrossRef] [PubMed]

37 Farias JR Andow DA Horikoshi RJ Sorgatto RJ Fresia P Dos Santos AC Omoto C Field evolvedresistance to Cry1F maize by Spodoptera frugiperda (Lepidoptera Noctuidae) in Brazil Crop Prot 2014 64150ndash158 [CrossRef]

38 Chandrasena D Signorini A Abratti G Storer NP Lopez Olaciregui M Alves AP Pilcher CDCharacterization of field-evolved resistance to Bacillus thuringiensis- derived Cry1F δ-endotoxin in Spodopterafrugiperda populations from Argentina Pest Manag Sci 2017 [CrossRef] [PubMed]

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41 Aguilera PA Vasquez CH Prueba de laboratorio con 30 insecticidas en larvas de Prodenia eridania (Cramer)(Lepidoptera Noctuidae) en alfalfa Idesia 1974 3 133ndash140

42 Gloria BR Control quiacutemico del gusano ejercito Prodenia sunia (G) en tomateira Rev Peru Entomol 1975 18120ndash123

43 Campos LE Toxicidad de cuatro insecticidas contra Spodoptera frugiperda (JE Smith) y Prodenia eridania(Cram) del Valle de Lluta Chile Idesia 1982 6 13ndash19

44 Savoie KL Alimentacioacuten selectiva por especies de Spodoptera (Lepidoptera Noctuidae) en un campo defrijol con labranza miacutenima Turrialba 1988 38 67ndash70

Insects 2018 9 93 12 of 13

45 Zenner de Polaniacutea I Aacutelvarez Rodriguez JA Areacutevalo Maldonado HA Mejiacutea Cruz R Bayona MASusceptibilidad de cuatro noctuidos plaga (Lepidoptera) al gene Cry1Ac del Bacillus thuringiensis incorporadoal algodonero Rev Colomb Entomol 2008 34 41ndash50

46 Santos-Amaya O Delgado-Restrepo O Arguumlelles J Aguilera-Garramuntildeo E Evaluacioacuten delcomportamiento del complejo Spodoptera con la introduccioacuten de algodoacuten transgeacutenico al Tolima ColombiaCorpoica cienc Tecnol Agropecu 2009 10 24ndash32 [CrossRef]

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50 Navarro FR Saini ED Leiva PD Clave pictoacuterica de polillas de intereacutes agriacutecola agrupadas por relacioacuten desemejanza INTA-EEA Pergamino Buenos Aires Argentina 2009 p 100 ISBN 978-987-521-344-9

51 Scalora F Casmuz A Cazado L Sociacuteas G Tolosa G Aralde M Guchea MA Fadda L Goacutemez MGoacutemez H et al Evaluacioacuten de diferentes insecticidas para el control de la oruga bolillera Helicoverpagelotopoeon Dyar (Lepidoptera Noctuidae) In El Cultivo de la Soja en el Noroeste Argentino Campantildea 20112012Devani MR Ledesma F Saacutenchez JR Eds Publicacioacuten Especial EEAOC nordm 45 EEAOC San Miguel deTucumaacuten Argentina 2012 pp 147ndash151 Available online httpwwweeaocorgaruploadpublicacionesarchivos28620121122085717000000pdf (accessed on 25 April 2018)

52 Muruacutea MG Cazado LE Casmuz A Herrero MI Villagraacuten ME Vera A Sosa Goacutemez DGastaminza G Species from the Heliothinae complex (Lepidoptera Noctuidae) in Tucumaacuten Argentina andupdate of geographical distribution of Helicoverpa armigera J Insect Sci 2016 16 1ndash7 [CrossRef] [PubMed]

53 Herrero MI Fogliata SV Vera A Casmuz A Sosa Goacutemez D Castagnaro AP Gastaminza GMuruacutea MG Biological characterization and mating compatibility of Helicoverpa gelotopoeon (D) (LepidopteraNoctuidae) populations from different regions in Argentina Bull Entomol Res 2018 [CrossRef] [PubMed]

54 Pietrantonio PV Junek TA Parker R Mott D Siders K Troxclair N Vargas-Camplis J Westbrook JKVassiliou VA Detection and evolution of resistance to the pyrethroid cypermethrin in Helicoverpa zea(Lepidoptera Noctuidae) populations in Texas Environ Entomol 2007 36 1174ndash1188 [CrossRef]

55 Gao Y Wu K Gould F Shen Z Cry2Ab tolerance response of Helicoverpa armigera (LepidopteraNoctuidae) populations from Cry1Ac cotton planting region J Econ Entomol 2009 102 1217ndash1223[CrossRef] [PubMed]

56 Liu F Xu Z Zhu YC Huang F Wang Y Li H Gao C Zhou W Shen J Evidence of field-evolvedresistance to Cry1Ac-expressing Bt cotton in Helicoverpa armigera (Lepidoptera Noctuidae) in northernChina Pest Manag Sci 2010 66 155ndash161 [PubMed]

57 Bird LJ Downes SJ Toxicity and cross-resistance of insecticides to Cry2Ab-resistant and Cry2Ab-susceptibleHelicoverpa armigera and Helicoverpa punctigera (Lepidoptera Noctuidae) J Econ Entomol 2014 107 1923ndash1930[CrossRef] [PubMed]

58 Breacutevault T Tabashnik BE Carriegravere Y A seed mixture increases dominance of resistance to Bt cotton inHelicoverpa zea Sci Rep 2015 5 9807 [CrossRef] [PubMed]

59 Reisig DD Reay-Jones FPF Inhibition of Helicoverpa zea (Lepidoptera Noctuidae) growth by transgeniccorn expressing Bt toxins and development of resistance to Cry1Ab Environ Entomol 2015 44 1275ndash1285[CrossRef] [PubMed]

60 Bernardi O Sorgatto RJ Barbosa AD Domingues FA Dourado PM Carvalho RA Martinelli SHead GP Omoto C Low susceptibility of Spodoptera cosmiodes Spodoptera eridania and Spodoptera frugiperda(Lepidoptera Noctuidae) to genetically-modified soybean expressing Cry1Ac protein Crop Prot 2014 5833ndash40 [CrossRef]

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62 Drees BM Rice ME The vertical beat sheet A new device for sampling soybeans insects J Econ Entomol1985 78 1507ndash1510 [CrossRef]

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63 Velasco de Estacul M Barral JM Orfila RN Taxonomiacutea especificidad y caracteres bioloacutegicosdiferenciados del complejo de especies denominadas ldquooruga del capullordquo del algodoacuten ldquooruga de la espigardquodel maiacutez ldquooruga del broterdquo del tabaco y ldquobolillerardquo del lino Rev Invest Agropec Ser Patol Veg 1969 619ndash68

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66 Fehr WR Caviness CE Burmood DT Pennington JS Stage of development descriptions for soybeansGlycine max (L) Merrill Crop Sci 1971 11 929ndash931 [CrossRef]

67 Kogan M Turnipseed SG Soybean growth and assessment of damage by arthropods In Sampling Methodsin Soybean Entomology Kogan M Herzog DC Eds Springer Press New York NY USA 1980 p 17 ISBN978-1-4613-8069-6

68 Zar JH Biostatistical Analysis Prentice Hall Upper Saddle River NJ USA 1999 p 750 ISBN-13978-0321656865

69 Di Rienzo JA Casanoves F Balzarini MG Gonzaacutelez L Tablada M Robledo CW InfoStat Versioacuten2008 Grupo InfoStat FCA Universidad Nacional de Coacuterdoba Coacuterdoba Argentina 2008

70 Justiniano W Fernandes MG Tigre Pereira Viana CL Diversity composition and population dynamicsof arthropods in the genetically modified soybeans Roundup ReadyregRR1 (GT 40-3-2) and Intacta RR2PROreg(MON87701 x MON89788) J Agric Sci 2014 6 33ndash44 [CrossRef]

71 Massoni FA Schlie G Frana JE Cultivo de soja Bt (RR2 PRO) y convencional (RR1) expuestos apoblaciones naturales de organismos plaga y depredadores Informacioacuten Teacutecnica de Cultivos de VeranoCampantildea 20132014 INTA-Estacioacuten Experimental Agropecuaria Rafaela Argentina Publ Misc 2015130 98ndash103 Available online httpwwwaapresidorgarwp-contentuploads201501Soja-Bt-vs-convencional-expuestos-a-organismos-plaga-y-depredadores_MASSONI_F-4pdf (accessed on 22 May2018)

72 Perotti E Russo R Loacutepez R Zari F Pradolini E Sanmarti N Maccari G Boero LGamundi J Evaluacioacuten de estrategias de manejo de refugios asociados a cultivos de soja Bt sobreplagas blanco no blanco y sus depredadores Para Mejorar Produccioacuten Cultivos Estivales 2014 52 177ndash182Available online httpintagobarsitesdefaultfilesscript-tmp-inta-evaluacin-estrategias-manejo-refugios-asociados-pdf (accessed on 22 May 2018)

73 Forti LA Sosa-Goacutemez DR Suscetibilidade relativa de Spodoptera frugiperda S eridania S albula S cosmiodese Anticarsia gemmatalis a os inseticidas chlorantraniliprole e flubendiamida In Proceedings of the 9th JornadaAcadecircmica da Embrapa Soja Londrina Brazil 12 June 2014 pp 126ndash129 Available online httpsainfocnptiaembrapabrdigitalbitstreamitem1058241JORN2014pdf (accessed on 22 May 2018)

74 Pastrana JA Los Lepidoacutepteros Argentinos Sus Plantas Hospedadoras y Otros Sustratos Alimenticios SociedadEntomoloacutegica Argentina Buenos Aires Argentina 2004 p 334 ISBN 987-21319-0-2

75 Sparks A A review of the biology of the fall armyworm Fla Entomol 1979 62 82ndash87 [CrossRef]76 Silva MD Bueno FA Stecca SC Andrade K Neves JOMP Oliveira NMC Biology of Spodoptera

eridania and Spodoptera cosmioides (Lepidoptera Noctuidae) on different host plants Fla Entomol 2017 100752ndash760 [CrossRef]

77 Angulo AO Olivares TS Weigert GTH Estados Inmaduros de Lepidoacutepteros Noctuiacutedos de ImportanciaAgriacutecola y Forestal en Chile y Claves Para su Identificacioacuten (Lepidoptera Noctuidae) Universidad de ConcepcioacutenConcepcioacuten Chile 2008 p 114

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