The Varroa Bee Mite

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Title:
The Varroa Bee Mite
Physical Description:
Fact sheet
Creator:
Sanford, Malcolm T.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

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Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"November, 1992"
General Note:
"ENY-127"

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Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
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IR00004413:00001


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TheVarroaBeeMite1 TheInstituteofFoodandAgriculturalSciencesisanEqualOpportunity/AffirmativeActionEmployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,ornationalorigin. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/JohnT.Woeste,DeanMalcolmT.SanfordandH.L.Cromroy2Varroajacobsoni ispotentiallythemostserious pestevertothreatenworldbeekeeping.Reports fromotherareaswherethemitehasbeenintroduced showthatgreatlossesofcolonieshaveoccurred.The samehasbeentrueintheUnitedStates. Itisimportanttoensurethat Varroa isnot confusedwiththehoneybeetrachealmite( Acarapis woodi).Therehasbeenandcontinuestobeagreat dealofcontroversyaboutthelattermitewhichlives inthebreathingtubesofbees.Thetrachealmiteis difficulttofindandthedamageitinflictsoncolonies isamatterofgreatdebate.The Varroa miteshould alsonotbeconfusedwiththebeelouse, Braulacoeca, whichhassixlegsthatextendfromthebody(Figure 1). The Varroa mite,bycontrast,isanexternal parasiteofthehoneybee.Itisvisibletothenaked eye(Figure2),reddishbrownwithacharacteristic ovalshapeandhaseightlegstuckedunderashell (Figure3). Somegeneralizationsconcerningthe Varroa mite whichhavebeentrueinotherinfestedareasofthe worldare: 1.RussianandEuropeanexperiencesrevealan infestationisusuallyfataltocoloniesofEuropean bees(Apismellifera)withinthreetosevenyears. 2.Lowlevelsofinfestationareextremelydifficultto detect.Figure1.Beelouse.(SEMphotobyH.L.Cromroyand W.C.Carpenter.)3.Itisa7-10yearprocesstogetchemicals registered,aprocessoftencostingmillionsofdollars. 4.Manyofthe140orsochemicalsusedworldwide forVarroamitecontrolaretoxictobeesand beekeepersandtheiruseriskscontaminationof honeyandwax. 5.The Varroa mitedevelopsresistancetochemicals inashorttime.Thisisespeciallytruewhenthe chemicalsarenotusedproperlyand/ordosagerates havenotbeenadequatelyinvestigated. 1.ThisdocumentwaspublishedNovember,1992asENY-127,andsupercedesHintsfortheHiveNo.127 ,FloridaCooperativeExtensionService. Formoreinformation,contactyourcountyCooperativeExtensionServiceoffice. 2.Professor,DepartmentofEntomologyandNematology,CooperativeExtensionService,InstituteofFoodandAgriculturalSciences,University ofFlorida,Gainesville.

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TheVarroaBeeMite Page2Figure2.Adultfemale,ventralanddorsalviews,comparingsizewithhindlegofworkerhoneybee.(SEM photobyH.L.CromroyandW.C.Carpenter.)Basedontheaboveinformation,severalthings areapparent.The Varroa miteisaseriouspest leadingtodeathofEuropeanbeesinmostcases. Mitepopulationsaredifficulttodetectinincipient stages,andmaytakeyearstobuilduptolevelswhere colonydeathisimminent.LIFECYCLEOFVARROANumerousstudieshavepiecedtogetherthelife cycleofthe Varroa mite(Figure4),butithasyetto beculturedartificiallyandmanyaspectsofits complicatedbiologyareunknown.Theadultfemale leavesthebroodcellandattachestoanadultworker ordronewhereshebeginstofeedbycuttingaholein theintersegmentalmembraneofthebee'shardouter skeleton.Littleisknownaboutthelengthoftime requiredforthisphase.Next,thewell-fedfemale dropsofftheadultintoabroodcellandhidesinthe broodfood(jelly). Normally,oncethebroodfoodisconsumedby thehost,thefemalethenbeginstofeedonthelarvae itselfbypiercingitsdelicateskin.Shethenlaysa numberofeggsofbothsexeswhichhatchintosixleggedlarvae.After48hours,thesebecomeeightleggedprotonymphswhich,afterfeedingonthebee larva,moltintoadeutonymph.Threedayslater,the lastmolttoanadultoccurs.Approximatelytwentyfourhourslaterthemitesmateinsidethecapped honeybeebroodcell.Themalesdieaftercopulation inthebroodcellandthefemalemitesemergeto beginthecycleagain. Thefemalemitedoesnotlayitseggsallatonce, butatprescribedintervals(SeeFigure4).This meansthatthelongerthebroodcycle,themoretime thereisforsubsequentmitestodevelop.Itisthought thatdronesarepreferentiallyparasitizedbecause theirdevelopmentalcycleislonger(24days)thanthat oftheworker(21days).Itisalsobelievedthatbees withshorterdevelopmentaltimes[ Apismellifera scutella,theAfricanhoneybee,andtheAsianbee, Apiscerana(Indica) ]aremoreresistantto Varroa becausemitepopulationsdonotdevelopasquicklyas intheEuropeanraces.CONTROLSTRATEGIESControlofthe Varroa mitemustbeaccomplished usingseveralstrategiesinconcertwitheachother, similartointegratedpestmanagementtechniques commonlyusedinmuchofagriculture.Dr.W.Ritter oftheGermanFederalRepublicin" Varroa Disease oftheHoneybee Apismellifera," BeeWorld,Vol.62,

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TheVarroaBeeMite Page3Figure3.Adultfemale,showingcurvatureofbodyandlegscoveredbytheshell.(SEMphotobyH.L.Cromroy andW.C.CarpenterNo.4,1981,pp.141-153)suggestsacombinationof thefollowing: 1.Developandusemoreeffectivetreatment methods. 2.Controlimportationofallspeciesofhoneybees. 3.Diagnoseinfestationsinthelatentstage(before damageisseen). 4.Isolateinfestedcoloniesandthoseinthe immediatearea. 5.Controlandcoordinatetreatmentofinfested colonies. AccordingtoDr.Ritter,theaimintheGerman FederalRepublichasbeentoisolatethesourceof infestationanderadicatethemiteinspecificlocalities. However,whereithasbeenspreadoverawidearea, infestationcanatbestonlybereduced,particularly wherethereareferalcolonies. Healsostatesthatunsuitablehighlytoxic substancesarecomingintouseandtheirimproper applicationcancontaminatehoney.Frequent underdosingcanalsoresultinresistantstrainsof mites,alreadyobservedinJapanwithphenothiazine. Frequentuseofchemicalscanalsomakebeekeeping unprofitable,saysDr.Ritter,andabiologicalcontrol shouldbeafirstpriorityinresearchforalong-range answerto Varroa control.CHEMICALCONTROLUsingchemicalstoreducemitepopulationscan innowaybecomparedtoexperiencesbybeekeepers withTerramycintocontrolAmericanfoulbrood. Therefore,beekeepersareurgednottousechemicals formitecontrolunlesstheyareregistered.Notonly isthepracticeofusingunregisteredpesticidesillegal, butitcanalsocreateundesirableeffects.Among thesearechemically-resistantmites,contaminatedwax andhoney,andsusceptiblelinesofbeeswhichare morepronetoparasitization.

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TheVarroaBeeMite Page4Figure4.LifeCycleof Varroa BeeMite. Again,itisemphasizedthatUSEofany unregisteredchemicalsbybeekeepersispotentially HARMFULtothebeekeepingindustry.Itshouldbe rememberedthatchemicalcontrolcanonlybe consideredashortrangeobjective--morelong-range researchwillberequiredtofindsuitablebiological controland/orresistantstrainsofbees.HONEYCONTAMINATIONAlthoughpesticideusemaybeimpermanent,or atbest,changingasmoreandmorechemicalsare usedformitecontrol,itisacertaintythatmoreand morehoneywillbescreenedforchemical contaminationinthefuture.Shouldpesticide contaminationbefound,theresultingadverse publicitycouldseverelydamagethehoneyindustry. Witnesstheuseofaldicarbonwatermelonsandthe Alar scareonapples.Ifthereisatradeoffbetween mitecontrolandcontaminationofhoney,thebias mustbeforprotectingthenameandreputationof honeyinthedecision-makingprocess.CONTROLBYMANAGEMENT/ MANIPULATIONExperiencehasshownthat Varroa mitecontrolis possiblebyreducingthemitepopulationsthrough management/manipulation.Becausethemiteneeds accesstobroodtocompleteitslifecycle,beescanbe removedfrombrood(broodlesstimesincoldclimates

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TheVarroaBeeMite Page5 mayalsobetakenadvantageof)foraperiodofdays byplacingtheminpackagesoremptyboxes. Adultbeesremovedfrominfestedcoloniescanbe establishedonfoundationorbroodlesscombthathas beenstoredforafewdaysandisfreeofmites. Othermanipulationsincludingtheuseofdrone combsas Varroa trapsandheattreatmentofinfested combsmaybeusefulforsmall-scalebeekeepers.SAMPLINGFORMITESBeekeepersareencouragedtoregularlysample theirownbeecoloniesforpresenceof Varroa inan efforttomonitormitepopulation.Thevideotape, VarroaMiteDetection,VT249isavailableonrequest bysendingablankVHStapetoExtension Apiculturist,POBox110620,Bldg.970,Gainesville, FL32611-0620. Adultfemalemitesarepaletoreddishbrownand measureabout1.1millimeterslongby1.5millimeters wide.Thefollowingmethodsarerecommendedfor detecting Varroa inacolony: 1.Examinationofhivedebris: Collectdebrisfromhivefloorwithbrushanddustpan andexamineonasheetofwhitepaper.Atleastone commercialbrandofmitedetectionboardisonthe market. 2.Examinationofadultbees: a.Collect50to100beesfromopenBROOD COMB.Placeinwashingsolution-gasoline,25% ethanolorisopropylalcohol,detergent-watermixture orhotwater,andshakevigorouslyfor1to10 minutes.Recovermitesbystrainingthroughfine screenmesh. b.Collect100livebeesfromopenBROODCOMB. Placeinsmallcagewithwiremeshbottomonwhite paper.Placeinovenat46-47degreesC.(114-120F.) for10to15minutesandexaminewhitepaper. c.Putabout1.3pint(200-300)oflivebeesfrom openBROODCOMBinaglassjar,addaonesecondsquirtofetherandalcohol(commercial enginestartingfluidscanbeused),shakeandroll beesaroundinjar.Lookformitesonsideofglass jar.Mitesarereddishincoloranduniformlyshaped. Itisemphasizedthatforalltestslistedabove,bees samplesMUSTCOMEfromthebroodnest,NOT theentrance. 3.Examinationofbroodcellsandcombs: a.Uncapbrood(dronebroodispreferredbythe mites,buttheycanalsobefoundonworkerlarvae) andremovewhitepupaewithforceps.Thedark coloredadultmitesareeasilyseenagainstthebee larvaeand/orpupaewhichareglisteningwhite.SANITATIONAlthoughthepossibilityof Varroa being transferredfromonehivetoanotherbyhumansis consideredslight,itcannotbetotallydiscounted. Adultmiteshavealsobeenfoundonotherinsects, butarenotthoughttobeabletoreproduceexceptin honeybeecolonies.Mitescannotliveifseparated fromhoneybeesformorethanfourdays.Mite infestedclothingstoredawayfromcontactwithbee coloniesthatlongwillnotcontaminateothercolonies.DAMAGEANDSYMPTOMSBeesintemperateclimateswithharshwinters appeartobemoreatrisk(i.e.dyingfromharsh conditions--winterloss)thanpopulationsinother climaticzones.Inhotclimates,wherebroodisreared yeararound,mitepopulationsreachtheirzenith soonerthanincoolerclimates.InFlorida,under idealconditionscolonydeathcanoccurwithin6-9 months.MostauthoritiesagreethatallEuropean bees(Apismellifera)thatbecomeinfestedwith Varroa mustbeconsideredinextremejeopardy. Itisemphasizedthatitmaytakealongtimefor themitepopulationtobuildtolevelswhereextensive damageisseen.Themostobservedsymptomofthe diseaseisdeformedlarvae,pupaeandadultbees, whichareoftenthrownfromthecolonyandcanbe seenneartheentrance. Thisinformationwasdevelopedbyaspecial Varroa MiteTaskForce,DivisionofPlantIndustry, FloridaAgricultureandConsumerServices.Itis beingmadeavailableelectronicallyandinprintbythe InstituteofFoodandAgriculturalSciences, UniversityofFlorida.