Proceedinqe of the 7th Iniernatumol Working Conference on Stored-product Protection - Volume 1

Control of stored product pests with Vlkane" gas fumigant(sulfuryl fluoride)

Bnan M. Schneider' and Preston L. Hartse1l2

Abstract

Vikane'" gas fumigant (sulfuryl fluonde) has been marketedfor over 35 years for control of structure mfesting msects,pnmanly drywood termites (Kalotemutidae) Vikane IS anIdeal fumigant for structural fumigation: however, effectivedosages for stored product pests have been determmed foronly a few species and lmuted temperatures ThIS paperpresents lethal dosage results reported as CT products(Concentration of Furrngant x Exposure TIme) m mg-h/Lfor the egg stage of several stored product msect pestsTolerance to VIkane mcreased as Plodui interpunctellaeggs aged. The P. interpunctella eggs were moresusceptible to Vikane than the three beetle species tested,with 98.4% control achieved at 238 mg- hlL. Troxxiermaixiriainle was the most tolerant species, at 2YC, a CT of619 mg 0 hlL was necessary to achieve 96 9% egg kill. ACT of 484 mg 0 hlL resulted m 95.1 % kill of Triboltumcasianeum. eggs, and a CT of 490 mg 0 hlL resulted in99 .5% kill of Trtboltwm confu.sum eggs The beetlespecies exhibited a flat dose response at higher dosagesAdditional tnals with refined dosages, shorter exposurepenods, and varying temperatures are necessary todetermine effective dosages across the range of expectedfield-use condrtions.

Introduction

Vikane'" gas fumigant (sulfuryl fluoride) has been marketedfor over 35 years for control of structure-mfesting msects,primanly drywood termites (Kaloterrmtidae ). Vikane IS anodorless, colorless fumigant composed of 99.8% SOzF1 ando .2% merts. Sulfuryl fluonde has a molecular weight of102.07, IS not very reactive, bolls at - 55. 2°C, has a vaporpressure of 13,442 mm Hg at 25°C, and IS soluble m waterto 750 ppm at 2YC (Dow AgroSCIences LLC, 1997).

1 Dow AgroSCIencesLLC, 9330 ZlonsVIlleRoad, Indlanapohs, IN46268 USA

2 DFA of Cahforma, 1850 S Van Nes..'lAve, Fresno, CA 93721USA

Because of these qualities, Vikane IS an Ideal Iurrugant forstructural funuganon: however, effective dosages for storedproduct pests, especially the egg stage, are only presentlybeing defined ThIS paper presents mtenm results oflaboratory chamber tnals conducted at the Dried Fruit andTree Nut Association of Cahforma (DFA) in Fresno, CA todetermine. 1) the lethal dosage of Vikane for the egg stageof several key stored product msect pests at 25°C, and 2)determme the relative susceptibihty of 1, 2, and 3-day-oldPlodui interpunctella eggs

Materials and Methods

Insect Preparation

Test msects were from cultures mamtamed at DFA fromstock origmally obtamed from USDA, ARS, Fresno, CA.Adult Indian Meal Moth, Plodm interpunctella, Red FlourBeetle, Tribolium. caetaneum , Confused Flour Beetle,Tribolium. confusum , and Warehouse Beetle (WE),Trogoderma vanabile were prepared for egg collection underenvironmental conditions of 28°C and 65% rh with aphotophase of 16 8 hours. Only eggs were fumigated.Previous research has shown this hfe stage to be the mosttolerant to Vikane (Kenaga , 1957; Thoms and Scheffrahn,1994) .Plodia interpunctella eggs were collected by placmg

adults m a 2 quart laying jar Stnps of paper towel (5.08 emx 15.24 em) for an adult resting SIte were taped to theinside bottom of the Jar (on top when inverted). The lid wascompnsed of a screen placed Just below a piece of 9 em filterpaper When the Jar was mverted the screen allowed theeggs to drop through to the filter paper. Eggs were thenwashed with water, and when pipetted, naturally stuck tothe filter paper The filter paper was cut mto piecescontammg ca. 200 eggs In some trials, egg age cohorts of1, 2, and 3 days + 12 h were created by removmgzreplacmgthe filter paper and addmg fresh adults daily.Active beetle adults (200 - 400) were placed m PetrI

dIshes contammg pre-SIfted (lOO-mesh) flour and held in anmcubator for 1, 2, or 3 days to ensure that eggs 1 - 3 daysold were present Beetle eggs were collected by passmgflour contaming eggs through 30, 50, and 60 mesh SIeves.The quantity of eggs per treatment were estimated based on

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Proceedings oj the 7 th Internatumal WorkLng Conference on Stored-product Protection - Volume 1

the number of eggs hatched in the controls Duringtreatment, plastic weigh boats (4.4 em square x 0.8 cmhigh) containing eggs and a small quantity of flour weretaped to the bottom of open Petn dishes. A hght coating ofrmneral oil was placed around the edges of the Petn dish toprevent neonate larvae from escaping.

Fumigation

Fumigations were conducted m 28.31 fiberglass chambersm a temperature controlled walk-m chamberConcentrations of Vikane were determmed dunng exposurem a manner similar to that descnbed by Tebbets et al( 1983) and Hartsell et al. (1986) except thermoconductrvitywas used for gas detection. Exposure durations were 48 hDosages were measured as CT products (Concentration ofFumigant x Exposure Time) expressed m mg • h/L(Munro, 1969).After an ~2h aeration period, the open Petn dishes WIth

eggs were placed m an incubator at ~ 28°C and 65 - 70%rho Egg hatch was recorded at least two times weekly posttreatment for a maximum of 4 weeks Percent mortality foreach treatment (dosage) was calculated as: :# treated eggshatched / :# control eggs hatched

Results and Discussion

Lethal dosages for these stored product pests were generallyconsistent WIth dosages reported for the egg stage of otherstored product pests (Bell, 1997 ; C Reichmuth,unpublished data; M. Scholler, unpublished data; Thomsand Scheffrahn, 1994).Exposure of Indian Meal Moth eggs to Vikane in aged (24

h) cohorts showed that 3-day-old eggs were more tolerant toVikane than 1 and 2-day-old eggs (Table 1) Bell (1997)and C. Reichmuth (unpublIshed data) reported thatMediterranean Flour Moth (Ephestia kuehsuella ) eggsusceptibility was also dependent on ageThe P. uiterpumctetlo. eggs were more susceptible to

Vikane than the beetle species tested, WIth 98.4% controlachieved at a CT of 238 mg·hlL (Tables 2 & 3).T sxiriainle was the most tolerant of the species tested,

With 96.9% control achieved at a CT of 619 mg· h/L (Table3)

A CT of 484 mg· h/L or less achieved at least 95.1 % killof T confusum. and T. castaneum eggs (Table 3).For T. confusum, 100% kill was achieved WIth a CT of

941 mg· h/L. The highest CT tested for T. casianeum ,1157 mg-h/L, achieved 99.8% kill The highest CT testedfor T. varuibile , 1195 mg-h-L, achieved 98% kill (Table3)

Vananon in susceptibility to Vikane across speCIes ISassumed to be dependent on dIfferences m egg shellpenetratIon, due to dIfferent sulfuryl fluonde bmdmg rates

in the egg shell and embryomc membranes (Outram, 1967).Add; nonal tnals WIth refmed dosages, shorter exposure

penods, and varying temperatures are necessary todetermme effective dosages across the range of expectedfield-use condrtions.

Table 1. Percent Mortality of 1, 2 and 3-Day-Old Ploduimierpunctetui Eggs Fumigated Separately with

Vikane® for 48 h at 30°C.

Concentration CT Product(rng/L) (rng- hlL)

Egg Age Percent

(days") Mortality"

1 100

2 98.6

3 73.7

1 98.7

2 97.8

3 86.9

1 100

2 100

3 97.5

1 100

2 100

3 98.0

1 100

2 100

3 98.0

5 227

10 525

15 640

20 1043

25 1180

aEgg ages: 1 day = 12h± 12h; 2 day = 36h± 12h; 3 day = 60h±12hb Mortahty based on the number of eggs hatched III the controls

Table 2. Percent Mortahty of Plodui mterpunctella Mixed-Age (1 to 3-Day-Old) Eggs Following Fumigation

WIth Vikane'" at 25°C.

CT Producta (rng- h/L) Percent Mortality

115

213

238

374

453

538

653

814

854

17.0

50.0

98.4

99.0

98.0

99.3

99.7

100

99.0

aAll fumIgatIOnexposures were 48 hr

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Proceedings of the 7 th International Working Conference on Stored-product Protection - Youome 1

Table 3. Percent Mortality of Triboluim. confusum ,Tribolium castaneum and Trogodermavariabile Mixed-Age (1 to 3-Day-Old) Eggs

Followmg Fumigation WIth Vikane® at 25'C .

CT Product":" TriboliumPercent Mortality

(mg-h/L) confusum Tribolium Trogodermacastaneum varwbile

233, 233, 238 60.6 83.9 13.8

490, 484, 514 99.5 95.1 31.3

624, 621, 619 99.5 98.9 96.9

792, 758, 814 99.7 98.9 96.9

941,910,950 100 99.8 97.4

1178,1157,1195 100 99.8 98.0

a First CT product for T. confusum , second for T castaneum ,third for T. mnafnlebAll fumigation exposure tunes were 48 hr.

References

Bell, C. C. 1997 The toxicity of Vikane (sulfuryl fluoride)to eggs of the mill moth (Ephestia kuehniella). Proc.1997 Annual International Research Conference on MethylBromide Alternatives and Emissions Reductions. San

DIego, CA Nov. 3 - 5.Dow AgroSciences LLC. 1997. Vikane Gas Fumigant -Structural Fumigation Manual. Dow AgroSciences LLC,Indianapolis, IN.Hartsell, P. 1., H D. Nelson, J. C. Tebetts and P. V.Vail. 1986. Methyl bromide fumigation treatments forpistachio nuts to decrease residues and control navelorangeworm, Amyelois transitella (Lepidoptera:Pyralidae). Journal of Economic Entomology. 70: 1 - 6.Kenaga, E. E. 1957. Some biological, chemical, andphysical properties of sulfuryl fluonde as an insecticidalfumigant. Journal of Economic Entomology. 50: 1 - 6.Munro, H. A. U. 1969. Manual of fumigation for insectcontrol, 2nd edition, pp 25 - 30. In FAO Agnc. Stud. 79.Outram, I. 1967. Factors affecting the resistance of insecteggs to sulphuryl fluonde - II: The distribution ofsulphuryl-P S fluonde in msect eggs after fumigationJournal of Stored Products Research. 3: 353 - 358.Tebbets, J. S., P.1. Hartsell, H. D. Nelson, and J. C.Tebbetts. 1983. Methyl bromide fumigation of tree fruitsfor control of the Mediterranean fruit fly: concentrations,sorption, and residues. Journal of Agricultural and FoodChemistry. 31 :247 - 249.Thoms, E. M. and R. H. Scheffrahn. 1994. Control ofpests by fumigation with Vikane gas fumigant (sulfuryl

fluoride). Down To Earth® . 49(2) :23 - 30.

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