SEMINAR IN-CHARGE

Dr. S.K. Shrivastava

Head of the Deptt.

Department of Entomology

PRESENTED BY

R. S. Marabi

Ph.D. (Ag.) Scholar

Roll No.:188

Credit seminar

on

Bemisia tabaci : An obnoxious insect pest

Department of Entomology

College of Agriculture, JNKVV, Jabalpur- 482 004 (M.P.)

Introduction

Whitefliesare Hemipteran insects which belong to family Aleyrodidae.They are small and typically feed on the undersides of plant leaves and suck the cell sap. It was first reported as a pest in 1919 in India (Hussain and Trehan, 1933). Since then, it has been recognized as a pest of crops in tropical and subtropical countries.

C.N.: Whitefly S. N.: Bemisia tabaci (Gennadius,1989)

Cont.

To date more than 1200 species of whiteflies have been identified .The genus Bemisia contains 37 species and is thought to have originated from Asia (Mound & Halsey, 1978). B. tabaci have wide host range of 506 species in 74 plant families (Greathead, 1986). It transmit over 200 different plant viruses belonging to the genus Begomovirus.So far about 6 biotypes of B. tabaci have been detected worldwide by molecular methods (Hilje, 2003).

Taxonomic position of Bemisia tabaci

Kingdom Animal

Phylum Arthropoda

Class Insecta

Division Pterygota

Sub-division Exopterygota

Order Hemiptera

Sub order-Homoptera

Family Aleyrodidae

Genus Bemisia Species tabaci

Geographical distribution

The B. tabaci is not genetically uniform. Based on mitochondrial DNA markers, the B. tabaci complex (comprising B and non-B type variants) can be placed into five major groups according to their geographical origin:

(1) New World (US, Mexico, Puerto Rico),

(2) Southeast Asia (Thailand, Malaysia),

(3) Mediterranean basin (Southwest Europe, North Africa, Middle East),

(4) Indian subcontinent (India, Pakistan, Nepal),

(5) Equatorial Africa (Cameroon, Mozambique, Uganda, and Zambia) (Frohlich et al.1999).

Species of whiteflies

Hilje (2003) reported that 1200 species of whiteflies worldwide and only three are recognized as a vectors of plant viruses:Cotton whitefly (Bemisia tabaci Genn.)Greenhouse whitefly (Trialeurodes vaporariorum West.)Silverleaf whitefly (B. argentifolii Bellows & Perring) Of this number, B. tabaci is considered the most important of the whitefly vectors of plant virus and the only species transmitting geminiviruses (Duffus 1987 and Harrison, 1985).

Behavior & population biology

Dispersal

Whitefly tend to remain in groups until the population becomes dense.

This means infestations stay concentrated in a few places, especially during the earlier stages of the crop.

Later as temperatures rise, they become more active and spread widely over the whole crop.

Adults are the most important dispersal stage.

Distribution

Only the first nymph (crawler) stage of whitefly is capable of movement, and this is limited to short distances, usually on the same leaf on which it hatched.

Adults of greenhouse whitefly only lay eggs on the young leaves at the top of the plant, so as the plant grows, younger nymphs are found on the upper parts of the plant and older ones are found lower down.

In contrast, sweet potato whitefly adults tend to lay eggs over the entire plant, so all life cycle stages can be found on the same leaf.

Morphology and marks of identification

Egg:

Adult females lay their elongated oval eggs on the undersides of the youngest leaves towards the shoot tips with the help of a short stalk.

Females may produce up to 300 eggs in their lifetime.

They are about 0.25 mm long and oval in shape.

For the first couple of days the eggs are transparent to pale cream-yellow, then after a day or two they begin to turn brown-black.

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Egg

Egg

Egg

Crawler (1st nymphal stage):

The egg hatches into the first instar which is mobile and called crawler stage.It is flat, oval, almost transparent and only 0.3 mm long with tiny legs that allow it to move across the leaf surface. It remains at this location until it turns into an adult. A modified alimentary system concentrates sugar in the interior midgut while the excess fluid is passed on to the midgut and excreted outside the body as honeydew.

Scale (2nd 4th nymphal stages):

When the crawler moults, it turns into a legless, 0.30.4 mm long, scale-like creature that is fixed to the leaf surface. The body is oval and almost transparent, although some yellow internal organs may be visible.

There are longer hairs on top of the body. It remains immobile, feeding off sap and moulting between nymphal stages (Reddy & Rao, 1989).

Cont

Pupa:

An oval, white case with a fringe of white threads projecting outwards around the body.The fourth nymphal stage starts off flat and oval. At the end of this stage it stops feeding, swells, becomes denser and forms waxy, spiny rods over its bodyAs a result it becomes creamy white in appearance and about 0.7 mm long.Shortly before it emerges parts of the adult, especially its eyes, can be seen through the pupa skin.

Cont

Adult:

The males are about 0.9 mm and females are about 1.1 mm long with a pale yellow body which remains covered with pairs of tent like white wings of uniform size. At rest, the wings are held in an inverted V position. Adult emergence usually takes place from their pupal case (pseudo-pupa) in the morning. Compound eyes of the adult are red colour.

Adult B. tabaci

Life cycle of B. tabaci

4-7 days

4-7days

2-3 days

2-4days

2-3 days

Inc. Metamorphosis

TLC- 15-18 days

(Temp. 25-32C)

Generation-11-15/year

Pupa

300 eggs

Weather factors

The availability of favourable weather (dry and humid) in recent years has paved the way for build up of whitefly population (Singh et al., 1998).The mild winter conditions in North India during the last two decades are known to trigger further carryover of whitefly.

Host plants of B. tabaci

S.No.Host plantsBotanical nameVegetable crops1TomatoLycopersicon esculentum2PotatoSolanum tuberosum3OkraAbelmoschus esculentus4RadishRaphanus sativus5CabbageB. oleracea var. capitata 6BroccoliB. oleracea var. italica 7CauliflowerB. oleracea var. botrytis8EggplantSolanum melongena9LettuceLactuca sativa

Cont

S.No.Host plantsBotanical nameCucurbits1MelonCucumis melo2WatermelonCitrullus lanatus3CucumberCucumis sativus4AyoteCucurbita moschataOilseed crops1SoybeanGlycine max2SunflowerHelianthus annuus3SesameSesamum indicumPulses1Common beanPhaseolus vulgaris2BlackgramVigna mungo3MungbeanVigna radiata

Cont

S.No.Host plantsBotanical nameTuber crops 1Sweet potatoIpomoea batatas2CassavaManihot esculentaFruits crops1PapayaCarica papaya2GuavaPsidium guajavaSpices crops1ChilliCapsicum annuum2Hot pepperCapsicum frutescens

Cont

(Devid, 2003)

S.No.Host plantsBotanical nameFiber crop1CottonGossypium hirsutumOther/forage/weeds 1TobaccoNicotiana tabacum2Alfalfa Medicago sativa3SidaSida rhombifolia

Nature of Damage

Whiteflies cause damage to the plant by two ways: Direct feeding: Introducing toxic saliva and decreasing the plants' overall turgor pressure. Both nymph and adult whitefly cause direct damage when they suck plant juices. As a result, infestations of whitefly can give plants a yellow, mottled look, stunting their growth, causing wilting and defoliation and thereby seriously reducing crop yield.

Cont

Nymphs of sweet potato whitefly inject enzymes that cause changes in the plants chemistry. The result can be irregular ripening of fruit which remain hard and sour tasting, with retarded internal colour.

SPFMV/SPFMV.htm

2. Indirect damage:

I. Sooty mold growth: encouraged by the honeydew secretion that block photosynthesis.

Leaves and fruits of tomato infected by honeydew of whiteflies

Cont

Cont

II. As a vector of plant viruses:

Transmission of plant viral diseases through adult whiteflies have the potential to cause crop losses indirectly by transmitting plant viruses.

Bean calico mosaic virus Arizona 1998

The ability of whiteflies to carry and spread disease is the widest impact on global food production viz; TYLcV, MYMV etc.

In the tropics and subtropics regions, whiteflies have become one of the most serious crop protection problems. Economic losses are estimated in hundreds to millions of dollars. Bemisia tabaciandB. argentifolii, transmitAfrican cassava mosaic, bean golden mosaic, bean dwarf mosaic,bean calico mosaic, tomato yellow leaf curl, tomato mottle, and otherBegomoviruses, in the familyGeminiviridae.

Cont

The worldwide spread of emerging biotypes, such asB. tabacibiotype B, also known as 'B. argentifolii', and a new biotype Q, continue to cause severe crop losses which will likely continue to increase, resulting in higher pesticide use on many crops (tomato, beans, cassava, cotton, cucurbits, potato, sweet potato, etc.).

Cont

Plant

Virus

(Astier et al., 2001)

Plant virus transmitted by insect vectors

55%11%11%9%7%5%2%

Plant virus transmitted by Bemisia tabaci

S.N.Host plantName of diseaseReference1Cassava (Manihot esculenta)African cassava mosaic virus (ACMV)Briddon et al.19902Potato Potato yellow mosaic virus (PYMV)Lazarowitz & Lazdins, 19913Tobacco Tobacco leaf curl virus (TLCV)Osaki & Inouye, 19814Cotton cotton leaf curl virus (CLCuV) Kapur et al. 19945Tomato Tomato yellow leaf curl virus (TYLCV) Tomato golden mosaic virus (TGMV), TLCV, TLCrVNoris et al.1998, Dry et al.19936Chilli chilli mosaic virus (ChLCV)Venkatesh, 19987Sweet potato Sweet potatoveinmosaic virus(SPVMV)Valverde, 2003

Cont

S.N.Host plantName of diseaseReference8Courgettes (Cucurbita pepo Squash leaf curl virus (SqLCV)Lazarowitz & Lazdins, 19919Beansbean golden mosaic (BGMV) viruses, MYMIVAzam et al.199410Poinsettia (Euphorbia pulcherrima)Euphorbia mosaic virus (EuMV)Martinez, 200011Gerbera (Gerbera sp.)Gerbera mosaic virus (GMV)Visalakshy, 200113OkraBhindi yellow vein mosaic virus (BYVMV)Briddon et al. 200114Lettuces (Lactuca sativa)Lettuce infectious yellows virus(LIYV)Martelli et al. 200216SoybeanSoybean crinkle leaf virus (SCLV) MYMIVBiswas and Varma ,200117CucumbersCucumbervein yellowingvirus(CVYV)Morris, 2006

Symptoms of plant virus caused by Bemisia

Cabbage leaf curl virus

Cotton leaf crumple virus

Tomato leaf curl virus

Potato leaf curl virus

www.apsnet.org

Cucumber mosaic virus

galleryhip.com

Bhindi yellow vein mosaic virus

Cassava yellows virus

www.apsnet.org

About 1200 whitefly species have been described (Anon., 2001, Mound and Halsey 1978), but relatively few transmit plant viruses. Economic losses which is caused by whiteflies are estimated in hundreds to millions of dollars. Only whiteflies in the Bemisia and Trialeurodes genera are virus vectors. B. tabaci has been of increasing importance as a pest and vector of virus diseases of plants since the early 1980s.

Pest status & economic importance

This has been due to the emergence of the B biotype and its rapid expansion in geographic distribution and host range. The whitefly transmit plant viruses in many region of tropical, subtropical arid and Mediterranean climates e.g. cassava, cotton, cowpea, cucurbits, crucifers, tobacco, tomatoes, potato, soybean, sweet potato, okra, lettuce, pea, bean, pepper, poinsettia and chrysanthemum are some of those crops that are vulnerable. In addition to outdoor crops, B. tabaci is also a serious pest protected environments, which enable it to survive during the winter in temperate climates in North America and Europe (De Barro, 1995).

Cont.

The global spread of the polyphagous B. tabaci biotype B as a "hitch hiker" on traded plant material is a major factor in the world wide increase in whitefly transmitted diseases. Changes in agronomic practices: Irrigated crops being grown for longer overlapping periods, monoculture, Resistance against injudicious use of insecticides have also been given as reasons for B. tabaci and its associated virus becoming major problems. (De Barro, 1995).

Cont.

Percentage of plant virus transmitted B. tabaci

(David, 2003)

Over 75% of plant viruses are transmitted by insects vectors (Hogenhout et al. 2008).Begomoviruses and whiteflies (9%) are a complex of viruses and vectors which threaten many crops worldwide. The specific cells of the whitefly, primary salivary glands control viral transmission specificity and that virion transport in the glands follows specific paths to reach secretory cells in the central region and then to reach the salivary duct.

Mechanism of plant virus transmission by Insect vectors

Results indicate that the secretory cells in the central region of primary salivary glands determine the recognition and transmission of Begomoviruses. These findings set a foundation for future research on circulative plant virus transmitted by arthropod vectors.

Cont

View of adult B. tabaci

Fig.: Showing the digestive system in a nongravid individual and the location of one primary salivary gland in the prothorax. Note: In gravid females the midgut was sometimes found in the thorax pressed against the primary salivary glands. AM- Ascending midgut; CA-Caeca; CC- Connecting chamber; CIB-Cibarium; DM-Descending midgut; EE- External esophagus; FC-Filter chamber; HG- Hindgut; PSG- Primary salivary gland; PSGD-Primary salivary gland duct; RS-Rectal sac; SEG- Subesophageal ganglion; TAGM-Thoracic abdominal ganglionic mass.

Typical feeding mechanism of sucking pests

Model of the ingestion-salivation mechanism of noncirculative, nonpersistent transmission.

Plasmalemma

Stylet

Cell wall

Stylet sheath

Virus

Ingestion from protoplast

Salivation into protoplast

Virus is ingested into the food canal (right), along with the cytoplasm. Virus adheres to the epicuticular lining of the food canal and the common duct at the very distal tip of the stylet, which is shared with the salivary canal. When the aphid first probes a cell after acquiring virus (left), saliva is injected into the cell. The watery salivary secretions will release virus from the cuticle lining the common duct, but virus farther inside the food canal would not be released by this mechanism.

Begomovirus s genomic organization

Mechanism of plant virus transmission

Bowdoin, 2013

Mechanism of feeding

Fig.: Showing the digestive system in a nongravid individual psg-primary salivary gland; e-esophagus; fc-filter chamber; mg-mid gut and hg-hind gut

Tomato yellow leaf curl virus

Management strategies of B. tabaci

Pyramid of IPM Tactics

Insecticides

Predators, parasites, microbials

Monitoring, Traps, barriers etc.

Field sanitation, plant variety, crop rotations etc.

Host plant resistance

*

Cultural Control

Clean cultivation:

Destruction of off-season host plants of whitefly.The removal of weed flora in/around the fields during the crop season e.g. Lantana sp., Solanum sp., Euphorbia sp., Datura sp. and Hibiscus sp. etc.

Barrier /Mulching:

Mulching with yellow polythene sheets delayed of tomato leaf curl virus (Cohen and Madjar, 1978).

Intercropping :

Cucumber planting in alternate rows 30 days before tomato, delay infection of TLCV (Al-Musa, 1982)

Mechanical control

Removal and destruction of first appeared plant with virus infection.Installation of yellow sticky traps.

ag.arizona.edu

Installation of yellow sticky traps in field

Monitoring of B. tabaci

Yellow sticky trap

Regular monitoring of B.tabaci apopulation should be done from the early stage of the crop. Yellow sticky traps can be use monitoring the pest population.

Fig.A) An adult big-eyed bug, Geocoris punctipes, B) Green lacewing larva, Chrysoperla sp., C) Pirate bug, Orius insidiosus feeding on preying on whitefly nymphs (http://en.wikipedia.org/wiki/Whitefly)

Biological control

Whitefly Parasites (Encarsia formosa Gahan-3rd) are the most cost nymphal and pupal effective biological control agent to control whiteflies. It is a aggressive, non-stinging parasitic wasp, which attract to its host by the actual smell of the honeydew produced by the pest, detecting this from several feet distance. Adult parasites will feed on this honeydew but also on pest body fluids through a hole made in the whitefly larvae.

Cont

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Botanical insecticides

Botanicals DosageRemarksReferenceNeemguard0.03%Moderate controlPuri et al. 1998; Dhawan, 1998, 1999, Mann et al. 2001NSKE5%--do--Neem oil 5%Rakshak Gold 1%0.5 lit./haEconeem 1%0.5 lit./haNimbecidine 0.003%5.0 Lit./haVery effectiveAchook 0.15%3.0 Lit./haVery effective

Chemical control

InsecticideDosageRemarksReferencesSeed treatmentImidacloprid 17.8 SL3.5 g/kg seedEffective only where WF is serious as early season pestRao et al. 1990; Jayswal and Sundaramurthy, 1992; Puri et al. 1998; Dhawan, 2000, Butter and Dhawan, 2001Thiomethoxam 70WS4.2 g/kg seed--do--Foliar sprayImidacloprid 17.8 SL0.5 ml/lit.Effective but Comparatively very costlyThiomethoxam 25 WG1000g/haEffectiveTrizophos 40EC600ml/haVery effective Ethion 50EC1000ml/ha

Resistance crop varieties against B.tabaci

CropCrop varietyReferenceCottonLK 861, Amravathi, Kanchan, Supriya and LPS 141Dhawan 1999 and Sharma, 2002,MungbeanML 337, ML 5, Mh 85-61 and Ml 325 BrinjalPusa purpleChilliHC 144Soybean JS 93-05, JS 97-52, JS 95-60SunflowerEC 93442Basappa and Sriharan, 1999

Biophysical bases of resistance against B. tabaci

CropResponseReferenceCotton Thinner and smooth glabrous leavesReduce host searching ability of parasitoidsNatrajan, 1990 and Rao et al., 1990Hairs and nongladular leavesLarge quantity of honeydew in hairs impede the parasitoidsLamina thickness Reduce feeding and oviposition abilitySponge tissue--do--Narrow leaves ResistanceCucumberNon grandular leavesResistance El Khidir, 1965

Cont.

CropResponseReferencePoinsettia Non grandular leavesResistanceBilderbac and Mattson, 1977TomatoGlandular leavesResistanceKishna, 1984SoybeanGlabrous leaves and hairsResistanceMcAuslane, 1996CabbageNon waxy leavesResistanceThompson, 1963

Biochemical bases of resistance against B. tabaci

CropNutrients/AllelochemicalEffect on insectReferenceCotton K,P, Mg, Gossypol, tannins, total sugars, flavonols, phenolsResistanceRao et al.1990MungbeanSugar amino acids ResistanceChhabra et al. 1988

Insecticide resistance management

The indiscriminate and non judicious use of insecticides particularly synthetic pyrethroids like cypermethrin, fenvalerate, deltamethrin and alpha-cypermethrin induces the resurgence of whitefly population due to increased fecundity and growth rate (Anonymous. 1989)The excessive use of insecticides like Acephate in late season also flares up the whitefly population beyond manageable limits (Dhawan et al. 2000).

As a result of development of resistance to different insecticides, the farmers apply several round of insecticides to obtain potential yield, which further led to the build up of whitefly population (Singh et al., 1999). Lack of appropriate spray technology for whitefly is also being considered as one of the important factors for giving further momentum in population build up of this notorious pest.

Cont

Alternative insecticide classes: To avoid or reduce the development of insecticide resistance in whitefly, different classes of insecticides should of apply. Integration of chemical tactics with other tactics. Timely application of insecticides.Insecticides also kill beneficial organisms: Only selective insecticides should be applied. Frequently and repeated spraying of insecticides from same chemical group should be avoided.

IRM strategies

Preserve susceptible genes: Preserve susceptible individuals within the target population by providing a haven for susceptible insects like: Such as unsprayed areas within treated fields, adjacent "refuge" fields, or habitat attractions within a treated field that facilitate immigration. These susceptible individuals may outcompete and interbreed with resistant individuals, diluting the resistant genes and therefore the impact of resistance.

Consider crop residue options:Destroying crop residue can deprive insects of food and overwintering sites. This cultural practice will kill insecticide-resistant pests (as well as susceptible ones) and prevent them from producing resistant offspring for the next season.

Classical findings against plant viruses

Cotton:

Cotton crop damage caused by CLCuV which is transmitted by whitefly.

Table: Economic threshold levels for cotton whitefly in India:

Threshold levelAreaReference20 nymphs/leafPunjabButter and Kular, 19866-8 adults/leafPunjabSukhija et al., 1986Appearance of honeydew symptoms on 50 % plantsPunjabDhawan, 199910 adults/leafAndhra PradeshReddy and Krishnamurthy, 19898-10 adults/leafTamil NaduSundaramurthy, 1992

Activity of whitefly in cotton zones in India

Northern Zone

Activity Period

May to November

Max. Activity Period

Sept. to Oct.

Central Zone

Activity Period

January to November

Max. Activity Period

Sept. to Dec.

Southern Zone

Activity Period

February to September

Max. Activity Period

Sept. to Jan.

(Dhawan et al., 2007)

Fig. Distribution of whitefly stages on canopy leaves

Canopy leaves

(Dhawan et al., 2007)

Population

Classical findings .

Soybean:

Yellow mosaic virus:

Causal organism- Mungbean Yellow Mosaic Virus (MYMV)

Alternative hosts: Vigna radiata, Alternanthera sessilis, Sida rhombifolia

Symptoms:

Disease first appears on young leaves with mottling of the leaves with an intense contrast between the yellow and the green areas.Yellow area are either scattered or produced in indefinite bands along the major veins. Rusty necrotic spots appears in the yellow area as the leaves mature.Under severe condition plants produces shriveled and lightweight seeds or sometimes fail to form flowers and pods.

Symptoms of virus transmission

Infected with Yellow vein mosaic virus

Management strategies of B.tabaci

MechanicalpracticesResistance /Tolerance var.Seed TreatmentSpray of InsecticidesDestruction of weed hostsJS 97-52, JS 93-05, JS 95-60Thiamethoxam (70 WS) 3.0g/kg seedMetasystox 25 EC 1.0 ml OR Imidacloprid 0.5 ml/liter water ORThiamethoxam (25WG) 100 g/ ha after 35 days of sowing.Removal of infected plants and burn them.

References

Dhawan A.K. (1999). Major insect pests of cotton and their integrated management. In: R.K. Updadhyay, G.K. Mukerji and R.L. Rajak (eds). IPM System in Agriculture Vol.6-cash Crops. Aditya Books Pvt. Ltd., New Delhi, pp.165-255.

Greathead,A. H. (1986). Host plants. In Bemisia tabaci-A literature Survey. M. J. W. Cock (Ed.), CAB International Institute of Biological Control, Silwood Park, Ascot, Berks.,UK, pp. 17 - 25.

Husain M.A., and Trehan K. N. (1993). Observations on the life-history, bionomics and control of white-fly of cotton (Bemisia gossypiperda M.& L.). Indian Journal of Agricultural Science 3: 701 - 753.

Natarajan K. (1990). Natural enemies of Bemisia tabaci Gennadius and effect of insecticides on their activity. J. Biol. Cont. 4(2):86-88.

Rao N.V. Reddy A.S. and Reddy P.S. (1990). Relative efficiency of some new insecticides to cotton whitefly, Bemisia tabaci Genn. Indian J.Pl. Prot. 18(1):53-58.

References

Dhawan A.K. (1999). Major insect pests of cotton and their integrated management. In: R.K. Updadhyay, G.K. Mukerji and R.L. Rajak (eds). IPM System in Agriculture Vol.6-cash Crops. Aditya Books Pvt. Ltd., New Delhi, pp.165-255.

Greathead,A. H. (1986). Host plants. In Bemisia tabaci-A literature Survey. M. J. W. Cock (Ed.), CAB International Institute of Biological Control, Silwood Park, Ascot, Berks.,UK, pp. 17 25..