Irradiation Control of Insect Pests

IrradiationControl of InsectPests

-ffisearcrrror of Dried Fruitsand Walnuts

nonchemical commodity

Scope of the Probtem Worldwide,approximately 1.2 million metric :il::::"-,,M ":,::;t*:r*i:rY.,H'*'*tons of raisinsand prunesand 574,000metric identified as an ozone dqrleter by the Montreal tons of walnuts(UNER 1994)are produced each driedfruits and Protocol (UNEB 1992).The resulting phaseout year.The U.S.is the largestsingle producer of dried fruits and walnuts, annually producing of this fumigant has encouragedfood procesmrs walnutsto consider more than 750,000metric tons worth more than to place more emphasis on alternative methods. $700million (USDA, i997). Most of this produc- inadiationas an Irradiation is one potential alternatirrc for dried tion is centeredin California. Significant production of raisins and prunes also occurs in Chile, fruit and nuts. Dornestic to alternative applications France,Australia, Greece,Mexico, South A-frica, disinfest newly harvested product or control and Turkey.Several thousand tons of &ied fus stor€e insects, as well as quarantine treatments and datesare produced in Middle Easternand Mediterranean countries. Walnut production is for orported product, have been considered. roughlythe samein China and the U.S.,with these In general,irradiation useselectromagnetic two countriesaccounting for about 75oloof the radiation of energylwels sufficignt to causedisin- worldt production (USDA, 1997).Other coun- festation of treated product without causingin- tries with significant wdnut production are Chile, duced radioactivity. It is rapid and efficaciousand France,India, Italy, and Turkey. ,UDYJOHNSON leavesno product residue.Ionizing radiation for Postharvestinsects cause losses to dried fruit AND MICH€LL€ usein food processingis produced by radioactive and walnut processorsthrough direct damageand HARCOTTE isotopes,machine-generated x-rays, or electron product contamination and by creating favorable accelerators.The sourceused most commonly in conditions for mold growth and product degrada- food irradiation is cobalt@.CesiumrsT and x-ray ir- tion. In the caseof walnuts, infestation by quaran- radiators havealso been usedto treat food, al- tined insectsmay also hinder international trade. though electron acceleratorsmay be a more likely Although it is difficult to accuratelyestimate in- alternative to cobale. dustry-wide costsfrom insect-relatedproduct loss Dried fruit and nut processorsin the United and control measures,they amount to millions of Statesare using phosphine fumigation irs a re- dollars eachyear in the U.S.alone. Currently, pro- . placement for methyl bromide wherever it is lo- cessorsuse fumigants to disinfest large volumes of gistically and economically feasible.New fumi- incoming product during harvest,as well as to gants,such as sulfi.rryl fluoride, methyl iodide, and control storageinfesations Methl bromide has carbonyl sulfde, may also prove usefirl. If so,radi- the advantagesof rapid treatment times, rdative ation is unlikely to be usedas a generalalternative. easeof use,and low cost. For an alternative to be However,should fumigant usebecome more reg- immediately acceptableto industry, it should have ulated or pestsdevelop resistanc€, other altema- all of the abovequalities. tives,including irradiation, may be considered-In other countries, and for applications such aspack- agedproducts or quarantine treatments where €fficocu of Rodiotlon Agoinst lnseets phosphine will not be acceptable,irradiation Extensivework has been done on the general could provide reliable pest control and reduce effectsof ionizing radiation on insects(Tilton and methyl bromide emissions. Brower, 1983).Insect responseto radiation de-

46 FOODTECHNOLOGY JUNEl9S). V01.53.N0.6 pends on the applied doseand the insect age.Navel orangeworm is also found in stageand speciesbeing treated.Undiffer- figs and occasionallyraisins. ln Califor- entiated,mitotically active tissuesare nia, newly harvestedwalnuts are fumi- most sensitiveto ionizing radiation. gatedto prwent further damageby feed- Consequently,eggs are normaliy the ing navel orangeworm larvae.An addi- mostsusceptible life stage,and adultsare tional fumigation is required as a quar- the most tolerant.Because insect gonads antine treatment against codling moth and midgut, both containing mitotically for walnuts going to ]apan. Husseinyand active tissues,are highly susceptibleto Madsen (1964) found that dosagesof radiationdamage, irradiated insects are 300 Gy applied to navel orangeworm often sterile and stop feeding soon after eggsor larvae prwented emergenceof treatment. Irradiated larvae may delay viable adults, but that 500 Gy applied to development,and may not die until they pupaewas neededto obtain sterile approachtheir next molt, resulting in in- adults.Johnson and Vail (1988,1989) sectssurviving for sometime after treat- showedthat feeding and damagecaused ment.The high dosesneeded to cause by navel orangeworm larvae could be re- immediatedeath of all insectstages are duced by as much as 78% with dosages rarely practical becauseproduct quality of300 Gy. suffers.For this reason,radiation treat- Researchon useofradiation against ments are designedto reduce product codling moth hasconcentrated on the de- damageby inhibiting insectfeeding and velopment of quarantine treatments.Bur- developmentand preventingpest popu- ditt and Moffitt (1985) showedthat non- lation growth by sterilizing adults. diapausingcodling moth larvaewere . Most insectsresponsible for signifi- Navel orangeworni larva more tolerant than diapausinglarvae, arrd cantpostharvest losses in dried fruits recommendeda doseof 145Gy asan ade- and nuts canbe separatedinto thoseat- quatequarantine treatment for apples. tackingproduct in the field andthose at- Burditt (1986)determined that 156Gy tackingproduct in storage.Although preventedemergence of normal adults most field pestsdo not continueto re-. from nondiapausinglanze in walnuts.A producein storage,they must be con- doseof 230 Gy wasnecessary to com- trolled in raw productcoming into pro- pietelyprevent emergenceof adults. cessingplants to preventadditional feed- Becauseof prolongedsurvival of in- ing damage.A few field pestsmay have secbafter radiation teatmslt, a major quarantinesignifi cance, requiring specif- considerationfor its useas a quarantine ic treatmentof the productbefore ex- treatrnentis the possibilityof live insects port. The most seriouspests are storage beingfound during inspectionsby the im- pests;their populationsare capable of porting counry. Currendy,there is no sim- continualincrease, and they aremost fruits, and may causeproblems in stor- ple method to determinethat an insecthas likely to be discoveredby consumers. agesituations. Papadopoulou (1964) beenin-adiated- This issueis being ad- The major pestsofpostharvest dried usedhigh doses(1.0-1.5 kGy) to obtain &essedand must be resolvedto make fruits,walnuts, and other commodi- immediate mortality in larvae and adult quarantineirradiation teatnents viable.It ties-the Indianmealmoth (Plodiainter- driedfr uit beede,Carp ophilus hemipterus. shouldalso be of concernfor domestic punaella) and the closelyreiated almond Broweret al. (1973)prevented adult de- treatrnert if it increasesthe dranceofthe moth (Cadra caurella)-infest product velopment from eggsand larvae of the consumer'sfinding a live insect. in storage.Generally, minimal dosagesof corn sap beede,Carpophilus dimidians, 200-250Gy havebeen suggested to pre- with dosesas low as 50 Gy. Iohnson Effectson Food Quotitg vent population development(Brower ( 1987) found that C. hemipteruswas Tastepanel studieson irradiated rai- and Tilton, 1970,1972;Ahmed, 1981), controlled readily with radiation doses sins and prunes after acceleratedstorage althoughto reducepost-treatment lon- of 300Gy. (Rhodes,1986) found that dosesofup to gevity a doseof 300 Gy may be more The sawtoothedgra n beetJe(Oryzne- 900 Gy did not causedeterioration in practical(Johnson and Vail, 1987; phil* suinamercis) often attacksdried quality, but some results were inconsis- Ahmed, 1981).This dosewill nor com- fruits in storage,and can be a severeprob- tent. Wahid et al. ( I 987) found that a pletely prevent feeding of late-stageIndi- lem in stored raisins.Brower and Tilton doseof 250 Gy had no significant effect anmealmoth larvae(lohnson andVail, (1970,1972)found that a doseof 200Gy on tasteof dried fruits evenafter 12 mo 1988),but it doesreduce product dam- preventedproduction of a secondgenera- of storage.They also found that radia- age(lohnson and Vail, 19E9).Wahid et tion. Papadopoulou(1964) obained tion significantly reduced ascorbicacid al. ( 1987)found that 250 Gy wasinsuffi- qui& control ofboth larvaeand adults of levelsin dried fruits, but noted that these cient to preventdevelopment of almond O. surinamensiswith 150Gy. changeswere not necessarilyof any nu- moth populationsin figs,unless coupled Infestations ofwalnuts by navel or- tritional signifi cance. with post-treatmentstorage at 20oc. angeworm (Amyelok transitella) an'dthe Auda and Al-Wandawi ( 1980) noted Nitidulid beetlesin the genusCa4po- codling moth (Cydiapomonella) otigi- that very high radiationdoses (l-10 philusare common field pestsof drying natein the field and arecarried into stor- kGy) causedsome significant amino acid

V01.53.N0.6.JUNE1999 FOODTECHNOLOGY47 phytosanitary or quarantine treatment of time, smaller on-site irradiators or re- Irradiation may be required, with the severity ofthe mote contract irradiators could be effec- treatment dependingon the require- tively usedfor outgoing packagedprod- Control ments of the importing country. uct. kradiation also has promise for use TTNUED Product handling methods wili dic- as phytosanitary and quarantine treat- Oor,r tate how easilyand for which applica- ments, becausea single treatment of out- tions irradiation may be used,Dried going product is sufhcient. Need for this fruits arrive at the processorin Iarge treatment would be limited to product lossesin dates,but the iosseswere great- biru, and most remain in thesebins exported to certain countries, and the ly reducedwhen the dateswere stored at throughout storage.Fumigants are ap- amount of treated product would be re- 0"C. However,dates are not usually a plied to &ied fruits, either to covered duced. Here, processorswould be unlike- valuablesource of amino acidin rnost stacksof bins in fumigation chambersor ly to use on-site irradiators; units located diets.Khan et al. ( 1985)found that radi- to entire warehouseor processingareas. at ports or contract irradiators would be ation generallyhad little effect on total Walnuts are often stored in bulk in large more efficient. acidity, color, or sugarlevels for several silos, although they may be kept for dried fruits, but that higher doses(0.5 some time in bins. Fumigants are applied Problemof Retreotment and 1.0kGy) adverselyaffected ascorbic to walnuts in silos,warehouse areas, or Under the storageprocedures cur- acid levels. fumigation chambers. rently usedby the industry reinfestation Commoditiessuch as walnuts, con- If irradiation is being consideredfor of the product by storagepests is likely. taining high levelsof unsaturatedlipids, disinfesting incoming product, facilities However,reirradiating the product poses are more likely than dried fruits to suffer must be capableof handling all harvest- logistical,economic, quality, and regula- oxidation,resulting in increasedrancidi- ed product within a short period of time. tory problems.Because product cannot ty and decreasedproduct quality. Taste Within California,product volumeis be irradiated while in storage,retreating panelstudies reported by Rhodes(1986) considerable,and would require individ- product would require moving the prod- found that radiation dosesof up to 900 ual units at eachprocessor, or one or uct bacJ<.through the irradiator. This Gy did not causeimmediate deteriora- more large, centrally located irradiators. would be particularly difficuit for walnuts tion in quaiity ofwalnuts, but that, with Use of remote irradiators to disinfest in- stored in silos.Retreatment would be even storage,some quality damageoccurred coming product is unlikely, however,be- lesslikely if product must be uansported at 600and 900Gy. Rhodes ( 1986)rec- causeof possiblereinfesation during to and from a remote irradiator. ommended that walnuts be irradiated at transport. The most-cost-effectivemetl- Given the barriers to reirradiation, lessthan 600Gy, preferably 300-450 Gy. od for handling incoming product might improving storagefacilities or combin- ]an * al. ( I 988)ev"aluated changes in be to treat a thin stream of product with ing irradiation with preventivetreat- iipids in walnutsirradiated at dosesof 0.5 an electron beam irradiator. This may ments would be necessary.TemPeratures and I 0 kGy and found no radiation-in- not be practical for dried fruits, asit re-

48 FOODTECHNOLOGY ( 1936).Although this report is 13 years try. Given problemsassociated with re- Irradiation old and cos* for irradiation and other irradiation, its usebecomes practical only treatmentshave changed,the work is when coupledwith sometype of protec- Control still interesting becauseit comParescosts tive measuredesigned to Preventteinfes- of alternative methods and combination tation, such ascontrolled atmospheres. TtNUED treatments.Costs for radiation varied Where rapid treatment is not critical, @otrt alone might be a with plant size,with Per-ton estimates controlled atmospheres being lower for larger plants. Control more economicaldternative for product developing countries, it would seemthat costsusing methyl bromide for walnuts' in storage,particularly in coveredstacks. theseoperational and safetyissues are raisins,or pruneswas $0.46-1.54lton/ When rapid treatment of relativelysmall manageable. year,regardless of plant size.Costs of us- amouns ofproduct is desired'particu- Of more concern maYbe accePtance ing radiation asa substitute for methyl larly of outgoing pa&aged product or by the consumer.Wthin the U.S" a small bromide on walnuts were estimatedat product needinga phytosanitarytreat- but vocal number of consumer advocary $8.32-71.89/ton/year.An alternative ment, irradiation may be a viable option. and environmentalgroups have ex- plan combining radiation with con- ln both cases,contract irradiators may be oressedconcern over the issueof controlled atmospherewas estimatedto cost the most costeffective. sumersafety (Sapp, 1995). While safety t6.52-66.96| totlyear. Costsof radiation are unfounded,the fear of pub- asa preshipmenttreatment for raisins REFERENCES concerns 1981.lnvestigations oninsect disinfes' (after Aimed,M.SH. lic outcry has causedthe food industry and prunes controlled-atmo- tationof dried dates by using radiation-A review. to be reluctant to adopt irradiation as a spheretreatment ofyard stacksand re- DatePalm J.1(1): 107-116. processingtechnique. Nevertheless, irra- frigeration during final processing)were AECL.1996. lrradiation otdried lruil and nJts as an al' diated produce is currently soid in about estimatedat $3.1i-19.93and $4.80- ternatvet0mew bromide.Application note. Atomic CanadaLtd., Nov Mississauga, Canada in the U.S.Midwest. The ap- 34.67 | tonl year,t espectively.Costs for Enemvof 80 stores lrLOa,tl. ano ru-wanoarvl, H.1980. Efiecl of 'v inadiation proval of irradiation in the U.S. for red controlled atmospherealone were and$orage mrdnions 0namino aciC mmpositjon of meat and a growing understanding $4.28-10.97,$4.214.88, and $3.90- somelaqidates JAgric tuod. Chem 26: 516-518 about food safety risks may lead to more 4.80/ton/year for walnuts, raisins, and Brower,J.H,, Miller, G.1., and Edenfield, JE 1973 com9p beetle, consumerand industry acceptanceof ir- prunes,repectively. Gammaradiation sensitivity 0fthe dinid@tus(Coleoplera: Nutidulidae) J and commodi- Canophilus radiation. Radiation equipment GeorgiaEntomol. Soc, 8{1): 55'58 Consumer acceptancestudies indi- ty processinghave changedsince the ErowelJ.H. and Tilton, E.W 1970. Insect disinfe$ation cate that the majority of conzumerswill abovestudy. Additionai analysisshould ofdrjed fruit by using gamma radiatjon. Food Inadia- eventually acceptirradiated foods. Mar- be done on the basisof current commer- tion11(1-2)i 10-'14. llfton,E.W 1972. Insed disinfestalion ket testsof irradiated foods worldwide cial practicesand fumigation costs,in- Brower,J.H. and ofshelled pecanq almonds and Mlnuts by gamma ra- have all been successfiI,and in numer- vestigatingoptions for irradiation at dif- 65:222'224. diation.J.Econ.'1995. Entomol. ous consumerresearch studies, the atti- ferent stagesof Product storageand Bruhn,Cl,/. Consumeraftitudes andmarl€t re- tudesof the majority of consumersare marketing and including scenariosfor sponsetoinadiated food. J. Food Protect. 58(2)l 175-181. often positive(Marcotte, 1995). Other improved storageto Prevent leinfesta- '1986. Burditt,A.K. Jr 1 lradialionasa quarantjnet%t- work indicatesthat accePtanceincreases tion. Comparison of radiation costs mofE(Lepi- mentfor walnub lnfesled wifi codling '1577-1579 when consumersare provided with in- with use of phosphine should be includ- dopb":Torticidae).J.Econ. Entomol, 79: formation about specific advantagesof ed, aswell as the use of contract irradia- Burdin,A.K. Jr. and Mofftt, H.R. l985 lnadiationasa the process(Bruhn, 1995;Resurreccion tors. quaantinefeatrnent for fruit subject toinfeshtion by larvae.In"Radiation Disiniestation 0f and Galvez,1999; Lusk et al., 1999). codlingmo$ Foodand Aoricultutal Products," edJ.H Moy, pp.87' Potentiot for lrlodiotion 97.Univ. otHawaii Press, Honolulu. €conomics When applied to dried fruits and Huss€iny,M.M. and Madsen, H.F. i 964, Sterilizatjon 0f Irradiation equipment caPableof walnuts, irradiation is a safeand effec- lhena!/el oangwortr.' Paranyelois tansitelk Wdk' processinglarge volumes of commodi- tive treatment method resulting in a e0,by gamma nadiation. Hilgardia 36(3): 113-137. Jan,[/., Lanqerak, DL., Wolters, lG., Falkas, J.,Kamo as dried fruits is caPital inten- product without chemical ties such high-quality H.J.,and. llluuse, B,G. 1988.]le effect of pacl€ging sive,with turnkey facility costsin the residues.An additional advantageto the andstorage condilions onthe keeping quality of wal- range of $4-7 million (leemhorst, method is its speedof application. Fu- nubtreated wih disinfestation doses 0l gammarays I 993). The costsof treating dried fruit migants typically take one or more days ActaAlimenbria 17(1): 13-31, oflaMe, pupae, and with acceleratorequipment or x-rays for complete application, and con- Johnson,J.A. 1987. Sensitivity adulbot tE driedftuitbeetle (Coleoptera: Nitidulidae) have been calculatedto be $ I .40/ton if trolled-atmospheretreatments take even togamma radiation. J.Econ. Entomol. 80:1302- all California commodities were irradiat- longer. However,tle advantagesof irra- 1305. ed at one plant, and $t-I0/ton if 5-r0 diation may be offset by difficulties inte- JohNon,J.A. and !hil, PV 1987. Adult emergence and facilitieswere built (AECI. 1995);the as- grating it into current industry sterilityofIndianmeal moths (Lepidoptela: ryralidae) ir- Practic- indried fruib and nuts J. Econ. En' increasein handling costswas are popular, in part be- radiatedasoupae sociated es,Fumigants tomol.80:497-501. not included in the anal)6is.Irradiation causetley cenoften be used to teat Johnson.J.A. and Vail, PV 1 988. Posttreafnent survlv- is more expensivethan fumigation, but product in place,in either covered al,development, andfeeding ofinadiated Indianmeal given the high value of dried fruit, irradi- stack, storagesilos, or warehouses, mothand navel orangeworm larvae (Lepidoptera: 376'380 ation costsmight not be prohibitive. making retreatment a simple matter. tonlidae).J.Econ, Entomol. 81: J.A.and Vail, PV 1989 Damage toraisins' al- would Joh'nson, An economic analysisof the use of h is unlikely that irradiation monds,and walnuls by inadiated Indianmeal moh and radiation specifically for California dried everbe a completesubstitute for fumiga- navelorangsworm larvae (Lepidoptera: ryralidae). J. fruits and nuts was done by Rhodes tion within the dried fruit and nut indus- Econ.Entomol. 82:1391-1394.

o 50 FOODTECHNOLOGY JUNE1999 V01.53,N0.6 Johnson,J,A,, Sode$trorn, E.1.,Curtis, CE., andVail, PV1995. Beyond metryl bromide: Non-chemical controlmethods for oostharvest 0ests 0f walnub, Aus- t'alianNutgrower 9(2): 19-20, Khan,1., Jan, M., Wahid, M., Neelofai Atta, S, Akhtar,I, andAhmad, A.198i . Radiationpreservation ofdrled fruitsin Pakistan. In"Seminar onFood lnadiation for DevelopingCountries inAsia and the Paciic, Tolqo,' pp.1-17. Food and Agric. Org./lnt. Atomic Energy Agenry,Vienna, Khan,1., Satbr, A., Wahid, M., and Jan, M. 1985, Radia, tiondisinfeshtion 0tdry fruits ln 'Radhton Disinfeslatjon ofFood and Aoricultural Producb,' ed. J.H. Moy, pp. 207-221. University ofHawaii Press, Honolulu, Hawaii. Leemhorst,J.G. 1993, Role of contract inadiators infood irradiation.h "Cost-Benefit Aspects ofFood lnadiation Processing,'Symp. Proceedings Int.Atomic Energy Agenry,Aix-en-Provence, March, Lusk,JL., fux, J.A., and Mcllvain, CL. 1999, Consumer acceptanceofinadiated meat. Food Tecfnol. 53(3): 56-59. Nlarcotte,M.1995, What Mve we learned aboul con- sumeracceptance ofiradiated f0ods? Nordion Inter- national,Kanata, Ontario, Canada. Papadopoulou,CP1964. Disinfeshtion ofdried figs by gammaradiation. InProceedings ofBadialion and Ra- dioisotopesApplied tolnsects ofAgricuftural lmpor tance,Athens, pp. 485-491, Intl. Alomic EnergyAgen. cy,Vienna, Austria. Resureccion,A,VA. and Galvez. ECF. 1999. Vvill comum- ersbuy inadiated beep food Tedrnol. 53(3): 52-55. Bhodes,A.A. 1986. lnadiation disinfestation ofdried fruitsand nuts. Afinal reporl. U.S. Dept. ofAgriculture, Agric.Res. Service and Econ. Res. Seruice. Washing- ton,D.C. Sapp,S.G. 1995. Consumer accephnce ofinadhted foods.,n"Food kradiation:A Sourcebook.," ed.E.A. Murano,pp.89-1 10. lowa State Univ. Press, Ames. Soderstrom,E.1.,Gardner, PD., Earitelle, J.1., de Loza- no,K.N., and Brandl, DG. 1984. Econornic costeval!, atjonof a generatedlow-oxygen atmosphere asan al, ternativefumigant inthe bulk storage ofraisins J.Ec0n. Entomol.77:457-461 Tilton,E.W and Brower, J.H. 1983. Badiation effects on alhropods.Chpt. 7 in'Preservation ofFood by lonizing Radialon,Vol. ll,"ed. E.S. Josephson andM.S. Peter son,pp. 269-316. CBC Press, Boca Baton, Fla. UNEP1992. Fourh meeling ofthe padies tohe N,,lont realProtocol on substances thatdeplete the ozone lay- Nations er.United '1994 Environment Program, Copenhagen. UNEP1994. Reportofthe Lilefiyl Bromide Tech- nicaiOptions Comminee forthe 1995 Assessment ol theUNEP Montreal Protocol onSubstances ttatDe- pletethe Ozone Layer United Natjons Environment Program,Nairobi, Kenya. USDA.1997. Agricultural sbtistics 1997. U.S Dept. of Agriculture,Natl, Agricultural Statistics Service, Wash- ington,D.C Wahid,lV., Sattat A,, Neelofar, Atta,S., Khan, 1.,and ' Ehiermann,D.A.E. 1987. Radiation disinfestation and quality0fdried fi-uits. Acta Alimentaria 16(2): '159- too. Wilson-Kakashita,G.,Gerdes, DL,, and Hall, W8. 1995. Theeffect of gamma inadiation onhe qualityofEn- glishwalnuF (Jugbns reglt?). Lebensm. Wiss, u. Tech- nol.2811)t17-29.

Theaukors kank Pat V Vail(USDUABS Fresno, Catif.), DonDerr Glen Burnie ltld.), and Guy Ha nan (USDA/ ARSWeslaco, Tex.) fot reviewinghis ma ,sdipt.

Edibd by ileil H, Memehtein, Seni6 Edibf O

VOL53. N0.6 . JUNE1999