MONTANASTATELIBRARY 31I0II861^*Hi0l0l0II9I119I2I0I1III9 MontanaDepartmentofAgriculture AgriculturalSciencesDivision TechnicalServicesBureau Helena,Montana 59620 AFIELDEVALUATIONOFZINCPHOSPHIDEOATBAIT FORCONTROLLINGBLACK-TAILEDPRAIRIEDOGSAND RICHARDSONANDCOLUMBIANGROUNDSOUIRRELS by MontySullinsandDanielSullivan STATEDOCUMENTSCOLLECTION FEB ?- 1397 MONTANASTATELIBRARY HELEN1A5,15MEO.N6TtAhNAAVE5.9620 ABSTRACT Fieldtrialswereconductedtodeterminetheefficacyofzincphosphideoatbaitsasa controlforblack-tailedprairiedogs{Cynomysludovicianus)andRichardson {Spermophilusrichardsoni)andColumbian(Spermopliiluscolumbiamis)groundsquirrels inMontana. Efficacywascomparedwhenzincphosphideoatbaitwasappliedwithand withoutanapplicationofnontoxicoatsasprebait. Zincphosphideefficacywasgreater than90percentontheprairiedogandRichardsongroundsquirrelwithprebaiting. Efficacywithoutprebaitingwasnotjudgedacceptable. Trialswithandwithouttheuseof prebaitpriortoapplicationofzincphosphideoatbaitforcontroloftheColumbian groundsquirrelwasnotfoundtobeefficacious. I , TechnicalReport95-02 July1995 I . ::\ - , L; '•-4*M1^^4 •":. *.•!»J•>>Vi.-'A4-(l^'.\'2-v-.’'^.^’^ ‘ ,' Si,’ '-iir’-.v/i •r' -v/, c ' , ' : #>>•’' ^i%•Aw’^4-^«,VL-^.~ ..*.• V^iv» V.-*5".‘-T*;'-V;••••^ >.^ • . ’-vi_‘ •-y'^.C-"'.’.r*-'V:..i«n.^?' *'5'-f-i’-•ht-.’V 4^ >^V. •«a.4> -r"^- i•*Vvs•r•}.'•'»;•;..'-; -.'<- V-^V Cir“ V* '' jrI'-s::'"''* J <'if•.' 'v\, i>* ".v•”? v\ w rj,- ,y7’ --,•-..t. -.>.'!,(t-..'¥;•.:.r'-''-'•'-&•-•..'. .'>* - .'•-AV""-":,, V •(. a -•*:-'.^. ^r.:^. ^.-'...W. AV...JT..^f§ .' ;i«v.«.-. .. w INTRODUCTION TheU.S.EnvironmentalProtectionAgencyhascanceledthepreviouslyandwidelyused fieldrodenticidessodiummonofluoroacetate(Compound1080)andstrychnineforabove grounduses. InMontana,onlytworodenticidesformulatedongrainbaitscontinuetobe registeredthatareeconomicalforlargeacreageapplication,zincphosphideand chlorphacinone. Zincphosphidehasbeenregisteredasafieldrodenticidesincethe 1940’sandhasbeenavailableinMontanatocontrolprairiedogsandgroundsquirrels. Zincphosphidebaitshavealonghistoryofpooracceptanceanderraticefficacy. Prebaitingzincphosphidebaitswithclean,nontoxicoatshasbeenalongrecommended practicetoincreaseefficacy,butthissignificantlyincreaseslaborandcostinitsuse. Asa result,zincphosphidebaitshavehadpooracceptanceamongusersoffieldrodenticides andhasnotbeenwidelyusedinMontana. HACCO,Inc.iscurrentlymarketingazincphosphidebaitthatisformulatedondehulled, rolledoatsthathavebeenbakedtoatemperatureof400°F. Thebakingprocess preventsgerminationoftheoatsandotherunwantedseedsthatmaycontaminatethe bait. Thecookingalterstheflavoroftheoats,reportedlyincreasingacceptanceand eliminatingorreducingtheneedtoprebaitbeforeapplication. Thefieldtrialsreportedoninthisstudywereconductedtotestthisclaim. OBJECTIVES Theobjectivesweretocomparetheefficacyofprebaitedandnon-prebaitedapplications ofHaccoroastedoatzincphosphidegrainbaitontheblack-tailedprairiedogandthe RichardsonandColumbiangroundsquirrels. STUDYAREAS PrairieDog: StudyplotswereestablishedonrangelandpasturelocatednearMoltapproximately25 milesnorthwestofBillings,Montana. ThefieldtrialwasconductedApril1-7,1995. RichardsonGroundSquirrel: Studyplotswereestablishedindryland,grasshayfieldsnearSheridanandWilsall, Montana. ThefieldtrialatSheridanwasconductedApril13-23,1995 Thefieldtrialat Wilsallwasconducted April 19-May5, 1995. ColumbianGroundSquirrel: StudyplotswereestablishedingrasshayfieldsnearDeerLodge,Montanaandfieldtrials wereconductedMay11-26,1995. 1 Vegetationoneachofthestudysiteshadbrokendormancyandwasgrowingresultingin anabundanceofgreenvegetationpresentateachsite. Theprairiedogsandground squirrelswereactivelyforagingonthegrowingvegetation. Noseedproductionwas occurringatanysitewhichprovidednopredispositionfortheprairiedogsorground squirrelstoforageongrains. METHODS Treatmentplotsandonecontrolplotwasestablishedateachstudysite. Abufferarea, surroundingeachbaitedplot,largeenoughtopreventimmediateimmigrationofthetest rodentsontothestudyplot,wasestablished. Thenumberoftestplotsestablishedvaried antonetaocxhicsirtoe.astAetdmoiatnsitmwuomdaatyseapcrhiosritteowaapsp:li1c.a)taiotnroefatHmeAnCtCplOotzpirnecbpahiotesdphwiidtehocalteabna,it (2%activeingredient); 2.) asecondplottreatedwiththezincphosphideoatbaitonly and; 3.) acontrolplotthatwasnotbaited. Baitandprebaitwerescatteredonbareor sparselyvegetatedgroundonthesurfaceneareachburrowentrancewithineachplotand itsassociatedbufferarea.Prebaitandbaitwereappliedbyhandusingcalibrateddippers toapplyoneteaspoon(5grams)ofbaitperburrowopening. Priortoapplicationofanybaitatthestudysites,baitacceptancetestwereconductedat eachstudysite. Baitacceptancetestswereconductedbyflagging20to30burrows spacedatleast25feetapart. Oneteaspoonofnontoxicoatswasscatteredina6inch baitspotbyeachmarkedburrow. Consumptionofthebaitwascheckedaftertwodays. Baitconsumptionoflessthan80percentwouldresultinpostponementofbait applicationuntiladditionalbaitacceptancetestsatdifferentburrowsresultedin acceptanceofbaitexceeding80percentwithintwodaysofplacement. Prairiedogandgroundsquirrelactivitywasmonitoredateachsiteandonallplotsby visualcountsusingbinoculars. Threecountsweremadefromthesamepointateach plotoneachoftwotothreedaysbeforeandaftertreatment. Thehighestnumberof eachofthepretreatmentandposttreatmentcountsprovidedaveragepretreatmentand posttreatmentactivityindices(AI). Percentreductioninactivityforeachplotwas calculatedusingtheformula: PretreatmentAI-PosttreatmentAI x 100 PercentReduction= PretreatmentAI Amountofbaitappliedandtimerequiredforapplicationwasrecordedforeachplot. RESULTS PrairieDog: Percentreductioninprairiedogactivityontwoplotsthatwereprebaitedwas90.5 percentand94.4percent. Thiscomparesto65.2percentand8^2percentreductionin activityontwoplotsthatwerenotprebaited(Table1). 2 Table1. Efficacyofzincphosphideoatbaitforcontrolofblack-tailedprairiedog andColumbianandRichardsongroundsquirrels. % Man Lbs.Bait Species Date Treatment Change Hours Used BillingsArea PrairieDog 4/5/95 w/prebait -94.4 3 6 PrairieDog 4/5/95 w/prebait -90.5 3.6 8 PrairieDog 4/5/95 w/oprebait -88.2 2.5 17.25 PrairieDog 4/5/95 w/oprebait -65.2 1.5 7 PrairieDog 4/5/95 Control -f9.0 - - SheridanArea RichardsonGdSq 4/21/95 w/prebait -96.3 7 9 RichardsonGdSq 4/21/95 w/oprebait -63.0 12 29 RichardsonGdSq 4/21/95 Control -2.5 - - WilsallArea RichardsonGdSq 5/1/95 w/prebait -95.6 8 24 RichardsonGdSq 5/1/95 w/oprebait -59.3 6 11 RichardsonGdSq 5/1/95 Control -3.9 - - DeerLodge ColumbianGdSq 5/19/95 w/prebait -58.4 4.5 12 ColumbianGdSq 5/19/95 w/prebait -48.1 6 10 ColumbianGdSq 5/19/95 w/oprebait -13.0 1.8 9 ColumbianGdSq 5/19/95 Control -t-5.0 - - RichardsonGroundSquirrel: Percentreductioninsquirrelactivityattwositesthatwereprebaitedwas96.3percent (Sheridan)and95.6percent(Wilsall). Zincphosphideappliedwithoutprebaitresulted inareductioninsquirrelactivityof63.0percent(Sheridan)and59.3percent(Wilsall). 3 ColumbianGroundSquirrel: PercentreductioninsquirrelactivityontwoplotsthatwereprebaitedattheDeerLodge studysitewas48.1percentand58.4percent. Thiscomparestoa 13.0percentreduction ( inactivityononeplotthatwasnotprebaited. ControlPlots-AllSites: Prairiedogandgroundsquirrelactivitydidnotsignificantlychangeonanyofthecontrol plotsduringthestudyperiods. Heavyrainoccurredattheprairiedogstudysite18hoursafterbaitapplication. Actual timethatthebaitwasavailabletotheprairiedogsduringtheiractivehourspriortothe rainfallwasabout6to8hours. Nosignificantrainoccurredonanyoftheground squirrelstudysiteswithinthreedaysafterapplicationofthezincphosphideoatbait. DISCUSSION Previousstudies(SullinsandSullivan,1990;Sullins,1980)haveshownthatzinc phosphidegrainbaitscanobtain90percentandgreaterefficacyonprairiedogsand Richardsongroundsquirrelswhenappliedwithprebaitandintheabsenceofgreen vegetation. Thesestudieshavealsoshownthatzincphosphidegrainbaitapplicationfor controlofprairiedogsandRichardsongroundsquirrelswhengreenvegetationispresent isoftenlessthan70percentcontrol. BecauseoftheColumbiangroundsquirrel’s hibernationbiology,itisseldomactivewhengreenvegetationisnotpresent. Efficacy trialswithzincphosphideontheColumbianhavebeenconsistentlyineffective. TheresultsoftheefficacytrialsconductedwithHACCOzincphosphideoatbaitwhen prebaitwasappliedresultedingreaterthan90percentcontrolofprairiedogand Richardsongroundsquirrelinthepresenceofgreenvegetation. Thislevelofefficacyis generallyconsideredexcellentwhencontrollingthesespeciestoreduceagriculturalcrop damagebeloweconomicthresholds. Theseresults,basedonthelimitednumberofreplicationsconductinthisstudy,show thatthisbaitcanbeefficaciousinthepresenceofgreenvegetationwiththeapplication ofprebaitforcontrolofprairiedogsandRichardsongroundsquirrels. Thesetrialswere conductedinthepresenceofgreenvegetation,butbeforetherewassubstantialgrowth. BaitapplicationduringlateMay,JuneandearlyJulywhenthereis significantlymorevegetationmaybelessefficacious. TheresultsintheRichardson groundsquirreltrialsindicatefairlydramaticallythatapplicationofprebaitisnecessary foracceptableresults. Theresultsintheprairiedogtrialswhereprebaitwasnotappliedaredifficultto interpretbutareconsistentwiththeerraticnatureofzincphosphideillustratedbyother studies. Rangelandsitesaregenerallylesslushthancropareasperhapsprovidingless competitionwiththebaitwhichmayimproveefficacy. Thisprobablydependsonvarying vegetationcharacteristicsofeachsite. Itisunknownwhateffecttherainsosoonafter 4 treatmentmayhavehadonefficacyattheprairiedogstudysite. ThetrialsconductedontheColumbiangroundsquirreldidnotshowacceptableefficacy. Thisillustratesthateachspecies,despitehowsimilartheymayappear,areuniqueand mustbestudiedseparately. Onehallmarkofagoodpesticideisthatwhenappliedaccordingtolabeldirectionsitwill achievegoodresultsconsistently. Webelievethatprebaitingandcarefultimingofthe baitapplicationwillbeveryimportantinobtainingconsistentandefficaciousresultsin mostsituations,particularlyifgreenvegetationispresent. Userswhoshortcut proceduresbynotprebaitingorwhodelaybaitapplicationtolaterintheseasonare likelytoexperienceerraticandlessthanefficaciousresults. Additionally,thereseemsto becertainunquantifiablevariables,bothbiologicalorenvironmental,thatdecreasethe efficacyofzincphosphideandthatarebeyondtheuser’scontrol. RECOMMENDATIONS 1. Zincphosphideoatbaitappliedwhengreenvegetationispresentshouldbe prebaited. 2. Baitapplicationshouldbeconductedearlyintheseasonwhencontrollingthe Richardsongroundsquirrelbutonlyaftertheentirepopulationofsquirrelsinthe controlareahaveemergedfromhibernation. 3. Adeterminationifthisbaitcanbeeffectivewithoutapplicationofprebaitwhen greenvegetationisnotpresentisneeded. Anecdotalreportsfortheprairiedog andRichardsongroundsquirrelindicatethatgoodresultsareobtainedwhenthe baitisusedindryconditionswithlittleornogreenvegetationpresentwithout prebaiting. Wehadhopedtotestuseintheseconditionsthisyearbutpersistent snowandrainduringearlyspringpreventedgettingintothefieldsooner. 4. Thesetrialsdonotprovideinformationtodetermineifthecookedoatsusedin theformulationofthisbaitresultsinbetteracceptancethatthesameoatsleft uncooked. Itwouldbeusefultodetermineifcookingtheoatsisacriticalfactor intheefficacyofthisbait. Thiscouldbedonebytestingefficacyofbait formulatedwithcookedoatsagainstbaitformulatedwithuncookedoats. Althoughcookingalsohasanimportantfunctionsinstoppingseedgermination, thisknowledgecouldhaveimportantapplicationsintheformulationofother rodenticidebaits. 5. Useofthisproductorotherzincphosphidebaitsisnotrecommendedforusedin controloftheColumbiangroundsquirrelifgreenvegetationispresent. LandownerusingzincphosphidebaitontheColumbianshouldbeadvisedto makeapplicationinaridsitesoraftercropshavebeenharvestedandthestubble isdryorinthecaseofforagecrops,beforeregrowthoccurs. 5 ACKNOWLEDGEMENTS WethanklandownersLeeLane(Molt),MelvinGoeffna(Wilsall),ChrisKoonce-Cal CreekRanch(Sheridan),JoeLaunderville-Grant-KohrsRanchNPS(DeerLodge)for usedoftheirproperties. MaxMerenz,MelvinGoeffnaandstaffofCalCreekRanch andGrant-KohrsRanchassistedwithbaitapplication. HACCO,Inc.providedthezinc phosphideoatbaitandfinancialassistancefortravelandperdiemexpenses. LITERATURECITED Sullins,M.andSullivan,D.1991. Afieldevaluationofzincphosphidebaitsfor controllingRichardsonandColumbiangroundsquirrels. MontanaDepartmentof Agriculture,TechnicalReport91-01. 7pp. Sullins,M.1980. Efficacyofstrychnineandzincphosphidebaitsforcontrolling Black-tailed PrairieDogs. MontanaDepartmentofLivestockReport. 3pp. 00172\vert\tr9502.dds 6