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The Sunflower Production Guide
INSECTS Thefollowingsectionsprovidecurrentinformationonmanagementofinsects,diseases,weedsandbirds.BelowisagrowingseasoncalendarthatshowsthemajorsunflowerpestproblemsandtimeofoccurrenceinthenorthernGreatPlainsproductionarea(Figure3).
Figure 3. A growing season calendar indicating time of occurrence of major sunflower pests. (J. Knodel, NDSU).
14|IntegratedPestManagement
APRIL MAY JUNE JULY AUGUST SEPTEMBER OCTOBER
Crop Stages
Weed Control
Insects
Diseases
Birds
Emergence Vegetative Bud Flowering Mature
CutwormsPalestriped Flea Beetle Budworm Moth Budworm – 2nd Generation Longhorned Beetle (Dectes) Stem Weevil Sunflower Beetle Adults Larvae Adults Sunflower Maggot Adults Larvae Sunflower Moth Adults Larvae Banded Sunflower Moth Adults Larvae Seed Weevil Lygus Bug Head Clipping Weevil Sunflower Midge Grasshoppers
Blackbirds
Downy Mildew White Mold, Rust, Verticillum Wilt Apical Chlorosis Phoma Black Stem Head Rot Alternaria Leaf and Stem Spot Premature Ripening
Preplant and Preemergence Post Emergence Final Weed Survey
CONTROL TIPS Iftheriskofwirewormdamageishigh,seedscanbetreatedwithanapprovedinsecticideforprotectionofgerminatingseedsandseedlings.ConsultthecurrentGuidetoCropProtection.Norescuetreatmentsareavailableforcontrollingwirewormsafterplanting.
Figure 4. Wireworm larvae
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The Sunflower Production Guide
SEEDLING AND ROOT FEEDERSWireworms
Wirewormlarvaefeedongerminatingseedsoryoungseedlings.Infestationsaremorelikelytodevelopwheregrasses,particularlyperennialgrasses,havebeengrowing.Stemsofyoungseedlingsmayemergeshreddedanddamagedplantsmaysoonwiltanddieresultinginthinstands.
Host Crops
Grasses,corn,carrots,potatoes,wheat,barley,pulsecrops,sunflowers,andmanyothercrops.
Biology
Wirewormlarvae(Figure4)areslender,smoothandhard-bodiedwire-likeworms varyingfrom1.5to2inches(38-50mm)inlengthwhenmature.Theyhave3pairsoflegsbehindthehead,areyellowishwhitetoacopperycolorandthelastabdominalsectionisflattenedandnotched.Itusuallytakes3to4yearsforwirewormstodevelopfromaneggtoanadultbeetle.Mostofthistimeisspentasa larva.
Boththewirewormadultsandlarvaoverwinterdeepinthesoil.Larvaemoveupanddowninthesoilprofileinresponsetotemperatureandmoisture.Aftersoiltemperatureswarmto50°F(10°C),larvaefeedwithin6inches(15cm)ofthesoilsurface.FromlateMaythroughJunethefemalebeetleslay200to1400eggsinloosesoilandunderlumpsofsoil.Whensoiltemperaturesbecometoohot(>80°F,27°C)ordry,larvaewillmovedeeperintothesoiltoseekmorefavorableconditions.Duetothis,wirewormsinflictmostoftheirdamageinearlyspringwhentheyarenearthesoilsurface.
Scouting Techniques
Soilsamplescanbecollectedandsievedinthespringtofindwirewormspresentinthefield.Soilshouldbesampledtoadepthof15cm(6inches)andrepeatedindifferentareasofthefieldtodeterminetheaveragenumberoflarvaepersquaremeter.Baitscanalsobeusedtoattractwirewormstoanareaformonitoring.Thepasthistoryofafieldisagoodindicator,especiallyifwirewormshavebeenaprobleminpreviousseasons.Croprotationmayimpactpopulationlevels.
Insects|15
The Sunflower Production Guide
Cutworms
Cutwormscanbeaseriousprobleminmanyfieldcrops.Therearemanydifferentspeciesinvolved,butthemostcommonaretheredbacked,darksidedanddingy cutworms.
Host Crops
Theredbackedcutwormfeedsinmostfieldcrops,vegetablesandhomegardenplants.Itisbestknownforfeedingoncereals,flax,canolaandmustard.
Biology
Cutwormlarvae(Figure5)havefoursetsofabdominalprolegsandcurlupwhendisturbed.Redbackedcutworms(Euxoa ochragaster)havetwobroadredorreddish-brownstripesthatextendstheentirelengthofthebody.Thetop-stripesaredividedbyadarklinewithwhiteinthecentre.Theheadisyellowish-brown.
Darksidedcutworm(Euxoa messoria)larvaearewhiteontheventralsidesandpalebrowndorsally.Theyhavenumerousindistinctstripes.Dingycutworm(Feltia jaculifera)larvaearedullbrown,withamottlecreamcolor.Thedorsalareaispalewithtracesofobliqueshading.
Cutwormmothsmaylayseveralhundredeggsinoronthesoil.Aftertheeggshatch,thelarvaefeedonthehostplants.Larvaenormallyhave6instarstages.Theymoultseveraltimes,eventuallyreachingaboutfivecentimeters(2inches)inlength.Thelarvaetunnelintothesoiltoformearthencellswheretheypupate andnewlyemergedmothsexitusingtheoldlarvaltunnels.Somespeciesoverwinteraseggs(e.g.theredbackedcutworm)oraslarvaeorpupae.StillothersdonotoverwinterinthePrairiesbutratherre-invadeannuallyfromtheU.S.,aidedbysoutherlywinds.Onegenerationofthisspeciesisproduced peryear.
Scouting Techniques
Cutwormsarenocturnal,feedingatnightandhidingduringthedaymakingthemhardtodetect.Oncethecrophasemerged,continuescoutingonaweeklybasisfrommid-Maytomid-June.Feedingbycutwormsresultsinnotched,wilted,deadandcut-offplants(weedsorcropseedlings).Plantsmaybemissingfromrowsandbarepatchesmayappearinfieldsasaresultofcutwormfeeding.Usingasmallgardentrowelandasoilsifter,cutwormscanoftenbefoundinthesoilaroundplantstheyhaverecentlydamaged.Cutwormsmaybe founddowntoabout5cm(2inches)belowthesoilsurface.Thesmall,worm-likelarvaecurluporattempttohideinthedebris.Pupaemayalsobecollectedinthisway.
16|Insects
Figure 5. Different species of cutworm larvae.
CONTROL TIPS Bestresultsoccurifinsecticideapplicationsaremadeintheevening.Sometimesitismosteconomicaltojusttreatinfestedpatchesandnottheentirefieldastherearedifferencesinsusceptibilitytoinsecticidesbetweenspeciesofcutworms.ConsultthecurrenteditionofGuidetoCropProductionforregisteredinsecticides.
Youngcutwormlarvaemaybestarvedbeforespringseedingbyallowingvolunteergrowthtoreach3to5cm(1.2to2inches),cultivatingandthenseeding10to14dayslater.Manypredaceousinsects,parasitesandbirdspreyuponcutwormsandreducetheirpopulations.
The Sunflower Production Guide
Economic Thresholds
Treatmentiswarrantedwhencutwormdensitiesexceed1cutwormpersquarefoot(30cmx30cm)orifthereisa25to30%standreduction.
Sunflower Beetle
Feedingbyadultbeetlesandlarvamayresultinpoorseedset,seedfilling,reducedyieldsanddelayedmaturity.
Host Crops
Sunflowerbeetlesfeedonnativeandcultivatedsunflowers.
Biology
Adultsunflowerbeetlesthorax(areabehindthehead)isapalecream-coloratthetopwithareddish-brownpatchatthebase.Eachwing-coverhasthreedark-brownstripesthatextendthelengthoftheback.Thefourthstripeendsatthemiddleofthewinginasmalldotthatresemblesanexclamationpoint.Sunflowerbeetlelarvae(Figure7)areyellowishgreenwithabrownheadcapsuleandhumpbackedinappearance.Newlyhatchedlarvaeareabout1.5to1.75mm(1/16inch)longandwillgrowtoabout8to10mm(underhalfaninch)whenfullydeveloped.
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Insects|17
Figure 6. Adult – Sunflower beetle
Figure 7. Larva – Sunflower beetle7
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The Sunflower Production Guide
Biology (Continued)
Sunflowerbeetlesoverwinterasadultsinthesoil.Usually,theiremergencefromthesoilinthespringcoincideswiththetimethatsunflowerseedlingsbegintoappearinlateMay.Thebeetlesfeedthroughoutthedayontheemergingseedlings.Eggshatchaboutaweekaftertheyarelaidandtheyounglarvaefeedontheleavesatnight.Theyhideamongthebractsoftheflowerbudandintheaxilsoftheleavesduringtheday.Thelarvaefeedforabouttwoweeks,butbecauseofthelongegglayingperiod,larvaemaybepresentinthefieldforaboutsixweeks.Thematurelarvaedroptotheground,enterthesoil,andpupateinearthencells.Thepupalstagelastsabouttwoweeks.AdultsofthenewgenerationemergeandfeedforashortperiodinlateAugustandearlySeptember.Theyfeedontheuppermostleavesorbractsoftheplantbeforere-enteringthesoiltooverwinter.
Scouting Techniques
Noticeabledamageisoftenfirstseenonplantsnearthemarginsofsunflowerfields.Whenplantsareseedlings,scouttodeterminetheaveragenumberofadultbeetlesperplant.Forlargerplants,determinetheaveragenumberoflarvaeperplantandpercentdefoliationbysampling20plantsat5sitesalonganXpatternforatotalof100plants.
Economic Thresholds
Thethresholdis1to2adultbeetlesperseedlingatthetwotosixleafstageor10to15larvaeperplantduringthesummer.Severeleafdamagemayoccurtoplantsinthetwotosixleafstageswhenadultbeetlesarenumerous.Controlmaybenecessaryifdefoliationcausedbyeithertheadultsorthelarvaereaches25to30percent,especiallyifmoredefoliationisexpected.Ifthemajorityofthelarvaehavereachedmaturityatabout25percentdefoliation,controlshouldnotbenecessary.
18|Insects
CONTROL TIPS Naturalcontrolsusuallykeepsunflowerbeetlepopulationsbelowdamaginglevels.Sunflowerbeetleeggsareeatenbythethirteenspottedladybeetleandtheconvergentladybeetle.Larvaeofthecommongreenlacewingconsumebotheggsandlarvae.Damselbugsandthetwospottedstinkbugmayalsopreyonlarvaeofsunflowerbeetles.Parasitoidsattacksunflowerbeetleeggs,larvae andadults.Insecticidesareavailabletocontrolsunflowerbeetle.ConsultthecurrenteditionoftheGuidetoCropProtectionforregisteredinsecticidesthatcontrolsunflowerbeetle.
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9
CONTROL TIPS Insecticideusehasnotbeenwarantedforcontrolofthistlecaterpillar.
Figure 8. Thistle caterpillar
Figure 9. Painted lady butterfly
The Sunflower Production Guide
Thistle Caterpillar
Thistlecaterpillar(Vanessa cardui)hasbeenanoccasionalpestofsunflowers.Localizeddamageofsunflowercropshasoccurredduringsporadicyearsofhighpopulations.
Host Crops
OnCanadathistle,larvae(Figure8)feedselectivelyonfoliage,leavingonlythestemandmidrib.
Biology
Adults,commonlyknownaspaintedladybutterflies(Figure9),arriveonthePrairiesduringearlyJune,dependingonspeedandpatternofmigration,fromoverwinteringsitesintropicalandsubtropicalareas.Thereisnoevidencethattheycansurviveourcoldwinters.ThisbutterflylayseggsonCanadathistleandabroadrangeofhostplants.Larvaefeedontheleavesproducingloosewebbing.Thelarvaeareupto30mm(1.25inches)longanddarkpurpletoblackincolor.Theyhavelongspinesoneachsegmentoftheabdomen.
Scouting Techniques
Ifpopulationsseemheavywhilescouting,sampleabout100scatteredplants,notingthepercentdefoliationoneach.Dividethetotalpercentdefoliationbythenumberofplantssampledtoobtainanestimateofpercentdefoliationforthe field.
Economic Threshold
Thethresholdis25percentdefoliationprovidedthatmostofthelarvaearestillunder3centimeters(11/4inches)long.Ifthemajorityoflarvaearefullygrown,mostofthefeedingdamagewillhavealreadyoccurred.
Insects|19
Figure 10. Adult Sunflower bud moth
Figure 11. Sunflower but moth larvae
Figure 12. Entrance hole of larva
Figure 13. Larva feeding results in deformations of the sunflower head, often a hole is formed.
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The Sunflower Production Guide
INSECTS IN THE STEM Sunflower Bud Moth
Highpopulationsofthispesthavebeenreportedinthepast.Despitehighpopulations,thesunflowerbudmothmaynotcausehighlevelsofeconomicloss.
Biology
Sunflowerbudmoths(Suleima helianthana)haveawingspreadofabout16to18millimeters(0.63 inches).Eachgray-brownforewinghastwodarktransversebands(Figure 10).Onebandextendsacrossthemiddleofthewing,andthesecondbandislocatednearthewingtip.Thelarva(Figure11)haveadarkheadcapsulewithasmooth,cream-coloredbody.
InManitoba,twogenerationsofsunflowerbudmothareproducedperyear.AdultsemergefromoverwinteringpupaeduringthelastweekofMaytomid-June.Afewdaysafteradultemergence,eggsaredepositedontheterminalsofimmaturesunflowersoronthereceptacleofmaturesunflowers.Eggsalsoaredepositedinleafaxils.Thehatchedlarvaebegintunnelingintothesunflowerplant.Theinitialinfestationinmid-Juneischaracterizedbyanentranceholesurroundedbyblackfrass(insectexcrement)(Figure12).Maturelarvaepupatewithinthesunflowerplant.Pupaemovetotheopeningoftheentranceholesformedinthestemorheadtissuesothatadultscanemergeeasily.ThesecondgenerationadultsappearinJulyandAugust.Infestationsbythesecondgenerationlarvaearenoteconomicallyimportant.
20|Insects
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The Sunflower Production Guide
Insects|21
Inearlyplantedsunflower,mostoftheinfestationsoccurinthestalks,whereasinlateplantedsunflower,mostinfestationsoccurinthepithareasofthehead.Theonlytimeyieldlossisnoticeableiswhenlarvaeburrowintounopenedbuds,preventingproperheaddevelopment.Thelarvaenormallydonotfeedondevelopingseeds,butconfinefeedingactivitiestothefleshlypartofthehead.Despiteminimaleconomiclosses,thelarvacausemalformationsinboththeheadandstalk(Figure13).
Scouting Techniques
Afieldmonitoringschemeforthisinsecthasnotbeenestablishedsinceitisnotofeconomicsignificance.
Economic Threshold – Nonehasbeendetermined.
CONTROL TIPS Insecticideusehasnotbeenwarrantedforcontrolofsunflowerbudmoth.
The Sunflower Production Guide
Sunflower Stem Weevil
Therearetwomainstemweevilsspecies,theSpottedSunflowerStemWeevilandtheBlackStemWeevil.
Biology
TheSpottedStemWeevil(Cylindrocopturus adspersus)adultsareabout4to5millimeters(3/16inch)longandgrayishbrownwithvaryingshapedwhitespotsonthewingcoversandbetweentheheadandabdomen.Thesnout,eyesandantennaeareblack.Thelarvaeare5to6mm(1/4inch)longatmaturityandcreamywhitewithasmall,brownheadcapsule.ThelarvaewillnormallybeinacurledorC-shapepositionwhenfoundinsunflowerstalktissue.ThespottedstemweeviladultsemergeinmidtolateJuneandfeedontheepidermaltissueofthesunflowerfoliageandstem.Thisfeedingdoesnotaffectplantvigor.Matingoccurssoonafteremergenceofadults.Justpriortoegglaying,femalesdescendtothelowerportionoftheplanttodepositeggsindividuallyintheepidermaltissueofthestem.Eggsareverysmall(0.51mmlongby0.33mmwide).UponhatchinginearlyJuly,thefirstinstar(larvalgrowthstage)larvaefeedonsub-epidermalandvasculartissue.Feedingisconcentratedinthepithtissueasthelarvaedeveloptothirdandforthinstars.
BythelastweekinAugust,thelarvaehavedescendedwhilefeedingtojustabovethesoilsurface.Arudimentarychamberisconstructedinthestem,andtheweevilsoverwinterinthischamberasfifthinstarlarvae.PupationoftheoverwinteringlarvaoccursthefollowingyearinearlyJune.Thereisonegenerationperyear.
TheBlackStemWeevil(Apion occidentale)adults(Figure14)areblackandonly2.5mm(0.1inches)longfromthetipofthesnouttothetipoftheabdomen.Thesnoutisverynarrowandprotrudesforwardfromthehead,whichissmallinrelationtotheratherlargebody.Thelarvaeareverysimilarinappearancetothespottedstemweevilexcepttheyareonly2.5to3mm(0.1to0.12inches)longatmaturityandyellowishincolor.
Theblackstemweeviloverwintersasadultsinsoil,plantresidue,sodandweedclusters.Uponemergence,theadultsfeedonvolunteersunflowersintheearlyseedlingstage.Adultfeedingoncultivatedsunflowerbeginsatthetwo-tofour-leafstage.Femalesdepositeggsundertheepidermisofthestem.Larvaeemergingfromtheseeggstunnelinthepithareaofthestem,pupateandemergeasadultsinearlyAugust.
LittleornoadultactivityisobservedforabouttwoweeksinlateJulyandearlyAugust.ApionadultsemerginginAugustalsofeedontheleavesandstemsoftheplant,butastheplantmaturesandtheleavesbegintodie,theadultsmoveunderthebractsofthesunflowerheadswheretheycanbeobservedfeedinguntiltheplantsareharvested.
22|Insects
The Sunflower Production Guide
Insects|23
ThesetwospeciesarehighlysuspectedinvectoringPhomablackstem,adiseaseinsunflowerfields.Theonlyspeciesofstemweevillarvathathasbeenfoundtocauseseriousstalkbreakageisthespottedstemweevil.Whenlarvalinfestationsofthisspeciesreach25to30ormoreperstalk,considerableweakeningofstemtissuecanresult,especiallywhentheselarvaebegintocreatetheiroverwinteringcellsinthebaseofthesunflowerstalks.Breakageismostlikelytooccurwhenplantsareunderdroughtstressand/orduringperiodsofhighwind.Thebreakagetypicallyoccursatorslightlyabovethesoilsurfaceincontrasttobreakageattributedtostalkdisease,whichnormallyoccursfartherupthestalks.
Scouting Techniques
LookforstemweevilswhenscoutingsunflowerfieldsinlateJuneandveryearlyJulyusingtheXpatternandexamining5plantsperstopforatotalof25plantsatthe8to14leafstage.Samplingsitesshouldbe75to100feetinfromthefieldmargins.Theaveragenumberofweevilsperplantcanthenbecalculated.
Whensurveyingforstemweevils,moveslowlytoavoidhavingtheadultstemweevilsdroptothesoiland‘playdead’.Adultfeedingbybothstemweevilspeciesisconsideredtocauseinsignificantmechanicalinjury.
Economic Thresholds
Theeconomicthresholdforthespottedsunflowerstemweevilisoneadultperthreeplants.
Figure 14. Adult Apion black sunflower stem weevil (NDSU).
14CONTROL TIPS NoinsecticidesarecurrentlyregisteredforcontrolofsunflowerstemweevilsinManitoba.DelayedplantingofsunfloweruntillateMayorearlyJunehasbeeneffectiveinreducingdensitiesoflarvaeinthestem.Falltillagepracticeswhicheitherburyorbreakupsunflowerstalkswillhelpincreasewintermortalityofstemweevillarvae.Naturalenemiesofthestemweevilincludethreespeciesoflarvalparasitoidsandoneeggparasitoid.Thesewaspshaveaccountedforapproximately30percentmortalityofthestemweevilsinthepast.
The Sunflower Production Guide
Sunflower Maggots
Therearethreemainspeciesthathavelarvalfeedingstagesthatcancauseseedsterilityorstalkbreakageunderhighpopulations.Damageisusuallynegligible.
Biology
Theadultformsofallthreesunflowermaggots(flies)havewingswithadistinctbrownoryellowish-brownpattern.Whileallthreeflyspeciesaresimilarinappearance,theydohavedistinguishingdifferences.
Sunflower receptacle maggot (Gymnocarena diffusa)
Thisspeciesisthelargestofthethreewithabodyabout10mm(0.4inches)longandawingspanofapproximately19mm(0.75inches).Theeyesofthisspeciesarebrightgreenandthewingshaveayellowish-brownandsomewhatmottledappearance.Sunflowerreceptaclemaggotlarvaeattainalengthofnearly8mm(0.31inches)atmaturity.Thelarvae(Figure15)taperfromthefronttotherearandareyellowish-whiteincolor.
AdultsofthesunflowerreceptaclemaggotemergeinlateJunetoearlyJulyaftersunflowerbudsreach5to10cm(2to4inches)indiameter.Eggsarelaidonthebractsofthedevelopingsunflowerheads.Egglayingoccursfrommid-JulythroughAugust.Thehatchedlarvaetunnelintothespongytissueofthereceptacle.Damagetotheheadisnegligible.After30days,thematurelarvaecutasmallemergenceholeontheundersideofthereceptacleanddropintothesoiltopupate.Overwinteringpupaearefoundabout19cm(7.5inches)deepinthesoilbyAugustorearlySeptember.Somelarvaewillpupateinthesunflowerhead.ThereisonlyonegenerationperyearinManitoba.
Sunflower maggot (Strauzia longipennis)
Adults(Figure16)ofthisspecieshaveawingspreadofabout13mm(0.5inches)andabody6mm(0.25inches)long.ThewingsbearbroaddarkbandsthatformafairlydistinctF-shapedmarknearthetips.Thelarvae(Figure15)ofsunflowermaggotarecreamywhite,headlessandlegless,asaretheothertwospecies.Theytaperslightlyatbothendsandattainalengthofabout7mm(0.28inches)atmaturity.
Sunflowermaggotshaveonegenerationperyear.Thisinsectoverwintersaslarvaeinplantdebrisinthesoil.PupationandadultemergencearecompletedinearlyJune.Femaleslayeggsinstemtissueofyoungsunflower,andlarvaefeedinthepithtissueformuchofthegrowingseason.
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The Sunflower Production Guide
Sunflower seed maggot (Neotephritis finalis)
Thissunflowermaggotisthesmallestofthethreespecieswiththeadulthavingabodylengthofabout6mm(0.25inches)andawingspanofapproximately7mm(0.28inches).Thewingshaveabrownlace-likeappearance.N. finalis larvaeattainalengthof4.5mm(0.19inches)atmaturity.
Unliketheothertwospeciesofsunflowermaggots,sunflowerseedmaggotscompletetwogenerationsperyear.Thefirstgenerationpupatesinthehead;thesecondgenerationoverwintersinthesoilaspupae.
Scouting Techniques
Scoutingtechniqueshavenotbeendevelopedforsunflowermaggotsbecausetheycausenegligibledamage.
Economic Threshold – Noneestablished.
Insects|25
CONTROL TIPS Insecticideshavenotbeenwarrantedforcontrolofthispest.
Figure 15. Sunflower maggot larva
Figure 16. Adult sunflower maggot
Figure 17. Sunflower maggot larval feeding causes deformations of the head.
The Sunflower Production Guide
INSECTS ON THE HEADSSunflower Midge
Midgelarvaecanaffectthegrowthofsunflowerheads.Heavily-damagedheadsbecomegnarledandcuppedinwardly,producingfewseeds.
Host Crops
Sunflowers
Biology
Thetiny,tan-colored,adultsunflowermidge(Contarinia schulzi)areonlyabout2mm(1/8inch)longwithawingspanofabout4mm(0.07inch).Thewingsaretransparentandvoidofmarkingsexceptfortheveins.Thefirstpeakoffirst-generationadultemergenceoccursinearly-tomid-July.Asecondpeakoccursabout7to10dayslater.Theadultsprefertolaytheireggsonsunflowerbudswithadiametergreaterthan1inch.Eggsarelaidindividuallyoringroupsindepressionsbetweenthebractsofthesunflowerbud.Themidgelarvaaretiny,beingonly3 mm(1/8inch)longwhenfull-grownandcreamtoyellowishorange.Thenewlyemergedlarvaemovetothebaseofdevelopingseedsorbracts.Presenceofthelarvaeisfrequentlydeterminedbynecroticareasatthebaseof,orbetween,bracts(Figure18).Theyusetheirraspingmouthpartstofeedontheplanttissuesintheselocations.Maturelarvaedropfromtheheadandburrowintothesoil.Ifconditionsarefavorable,theypupateandemergethesameseason.Otherwise,theyremaininthesoilandoverwinteraslarvaeincocoonsor,insomecases,aspupae.Thesecondgenerationadultslaytheireggsamongtheseeds.Usually,thelarvaepupateinthespring.TheadultsstarttoemergeinlateJune.Theadultmidgeonlylivefortwotothreedaysandaredifficulttofindinthefield.
Scouting Techniques
Althoughdamagemaybesevere,itisusuallysporadicandlocalized.Damagetoheadsisusuallyrestrictedtofieldmarginsbut,insevereinfestations,damageispresentthroughoutthefield.Whenmonitoringsunflowerheads,lookformidgelarvaeintheflowerhead,scarredbracts,andtwistedorgnarledflowers.Thelarvaemaybefoundatthebaseofthebractsorfeedinginthefloweratthebaseoftheflorets.A10xmagnifierhelpsinlocatingthetinylarvae.
Economic Threshold
Nothresholdhasbeenestablishedforthispestineitheroiltypeorconfection sunflowers.
26|Insects
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The Sunflower Production Guide
CONTROL TIPS Delayedplanting(untillateMay)mayavoidthefirstmajoremergenceoftheoverwinteringpopulation.However,laterinfestationscanstillbesevere.
Somecommercialhybridsaretoleranttosunflowermidge.Consultyourlocalseeddealerforinformationonthemostresistantvarieties.
Insecticidesdonotworkwellagainstthispest.Theyprovideinconsistentandinadequatecontroloftheadultsandlarvae.Becausethelarvaecrawlintothebudsoonafterhatching,theyareprotectedfromfoliarapplications.Insecticidescancontrolthesunflowermidgeonlyiftheyareappliedtothefoliagejustbeforetheadultsemerge.However,becausethisemergencecannotbeaccuratelypredicted,insecticideapplicationsareineffective.
Figure 18. Larvae feeding causes brown necrotic spots at the base of the bracts.
Figure 19. Severe midge damage causes over growth of the sunflower head.
Insects|27
The Sunflower Production Guide
Sunflower Seed Weevils
Larvaefeedonkernels,causingreducedseedweightandoilcontent.Oftenthekernelsareonlypartiallyfedupon,makingitdifficulttoseparatehealthyfromweevil-damagedseed.Thiscausesdowngradingofconfectionarysunflowerseed.
Host Crops
Sunflowers
Biology
TherearetwospeciesofSeedWeevilsthatcancausedamageinsunflowersinCanada;theredsunflowerseedweevil(Smicronyx fulvus)andthegraysunflowerseedweevil(Smicronyx sordidus).TheredsunflowerseedweevilisthemostcommonofthetwospeciesonthePrairies.Theadults(Figure20)are2.5to3.06mm(1/10to1/8inch),longandarecoveredwithreddish-orange,ovalscales.TheadultsappearduringlateJuneonvolunteersunflowersandfeedonthebractswheretheyformpinpointholes.Asthebuddevelopsandopens,adultsmovetotheinflorescenceandfeedonpollenproducedbythediskflowers.Femaleslaytheireggsinsidetheseedcoatofdevelopingseeds.Populationsarehighestonplantsat50%flowering.Theegglayingpatternfollowsseedfillingwhichprogressesfromtheoutsidetothecenterofthehead.Usually,aninfestedseedcontainsasinglelarva.Thelarvaearesmall,creamcolored,leglessandC-shaped.InlateAugust,thematurelarvaechewanexitholeintheseed,droptothegrounddirectlybeneaththesunflowerhead,andoverwinterinthesoil.
Thegraysunflowerseedweevilisnotascommonandisslightlylarger(3to3.5 mmor1/8inchlong)thantheredseedweevillarvae.Seedsinfestedbythelarvaeenlarge,protrudingabovethesurroundingseeds,andlackakernel.Thedamagecausedbyasinglelarvaofthisspeciesexceedsthatoftheredseedweevilbecauseofthelossoftheentirekernel.However,itusuallydoesnotcauseeconomicdamagetosunflowersusedforoilbecauseofitslowpopulationlevelandlowreproductiverate.
May June July August September
Larvae overwinter in soil
Larvae pupate, new adults feed on volunteer sunflowers
Females lay eggs in developing seeds, eggs hatch
Larval feeding, larvae move into soil
Larvae overwinter in soil
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CONTROL TIPS
The Sunflower Production Guide
Scouting Techniques
Beginscoutingforseedweevilsassoonastheyellowraypetalsappear.Continuecountsuntiltheeconomicthresholdlevelhasbeenreachedormostplantshavereached70%pollenshedatwhichtimeveryfewseedsaresuitableforegglaying.
Whensampling,followanXorZpatterninthefield.Initiatecountsmorethan100feetintothefieldascountstakenalongthefieldmarginwillleadtoabnormallyhighweevilcountsthatwillnotberepresentativeofthefield.Countthenumberofweevilson5plantsateachsiteforatotalof25plants.BrushthefaceoftheheadsvigorouslytobringtheweevilstothesurfaceorspraymosquitorepellentcontainingDEETonthehead.Thiswillforcetheweevilstomoveoutoftheirhidingspots.Careshouldbetakentonotconfuseotherinsectswhichmaybepresentonsunflowerheads,suchasminutepiratebugs(Figure21)forseedweevils.
Economic Thresholds
Inoilseedsunflowers,thethresholdis10to12weevilsperplant.Inconfectionsunflowersthethresholdis1to2weevilsperplant.
Figure 20. Adult Red Sunflower Seed Weevil
Figure 21. Sunflower seed weevils on top and the much smaller minute pirate bug nymphs below.
Insects|29
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Earlyplantinghelpsreduceseeddamage.Whenplantedearly,thesunflowersarecompletedanthesis(flowering)beforepeakweevilpopulationsandarenolongersusceptibletoegglaying.
Insecticides,sometimesincombinationwithtrapcropping,remainsthemajormanagementtool.Determinetheaveragesunflowerplantgrowthstagebeforeapplyinganinsecticide.TheweevildoesnotbegintolayeggsonsunflowerheadsbeforeR5.4(theouter40%offloretshaveopened).Iftreatmentisnecessary,insecticidesshouldbeappliedbeforethreeoutoftenplantsreach40%bloom.
The Sunflower Production Guide
Banded Sunflower Moth
Larvaefeedonsunflowerfloretsandseeds.
Host Crops
Commercialsunflowers.Severalspeciesofwildsunflowersarealsoknownhostsofbandedsunflowermoth.
Biology
Thebandedsunflowermoth(Cochylis hospes)isasmall,straw-coloredmothabout7mm(0.3inch)long(Figure22)withabrowntriangularareainthemiddleportionofthefrontwings.Newlyhatchedlarvaeareoff-whitewithadark-brownheadcapsuleandabout1.5mm(0.06inch)long.Asthelarvaegrow,thereisagradualcolorchangetolightpinkoryellow,thentoreddishorpurplishandfinallytogreenatmaturity(Figure23).Full-grownlarvaeareabout10mm(0.4inch)long.
Theadultmothsstartemergingfromthesoilinmid-Julyandarepresentthroughtomid-August.Mothsflyfromlastyear’ssunflowerfieldstothecurrentyear’ssunflowerfields.Adultmothsrestinvegetationalongfieldmarginsduringthedayandmoveintothefieldtolayeggsattwilight.Theylayeggsonthebractsofsunflowerheads.Eggshatchin5to8days.Larvaecanbepresentinsunflowerheadsfromaboutmid-Julytomid-September.Maturelarvaedroptothegroundandspincocoonsinthesoilwherewinterispassed.PupationtakesplaceinlateJuneorearlyJulythefollowingyear.
Newlyhatchedlarvaemovefromthebractstothefloretsofthesunflowerhead,wheretheyenteropenfloretstofeed.Ifeggshatchpriortotheopeningoftheflorets,larvaewillfeedonbracttissuebeforemovingtotheflorets.Larvaecontinuetofeedinthefloretsuntilthethirdinstar,reducingthetotalnumberofmatureseedsproduced.Duringlaterstagesofdevelopment,thelarvaetunnelthroughdevelopingseeds,usuallyenteringatthetopandleavingafterthecontentsareeaten.Eachlarvamaydestroy6to7matureseedsinadditiontothefloretseatenbytheearlierinstarlarvae.Sincetheseedkernelisentirelyconsumedbythelarva,theseedwillnormallypassthroughthecombine.
Thegreatestdamagebybandedsunflowermothlarvaehasbeenshowntooccurattheedgeofthefield.
Scouting Techniques
Fieldsshouldbemonitoredwhenplantsareinthelatebud(R-4)toearlybloomstage(R-5.1)ofdevelopment.
Monitorforadultmothsinearlyeveningorearlymorningwhenthemothsaremostactive.Samplingsitesshouldbeatleast75to100feet(23to30m)fromthefieldmargin.Countmothson20plantsfrom5differentsitesforatotalof100plants.
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CONTROL TIPS Iftreatmentiswarranted,itshouldbeappliedattheR5.1sunflowerplantgrowthstage.Insecticidesshouldbeappliedearlyinthemorningorlateinthedaytominimizetheadverseeffectonbeesandotherpollinators.Parasiticwaspsattackboththeeggsandlarvaeandgeneral
predatorsinthesunflowerfieldalsoconsumebothlarvaeandeggs.Minutepiratebugsfeedontheeggsandyounglarvae.Groundbeetlescandestroyabout40%ofoverwinteringlarvaeandpupae.Atleast4differentspeciesofparasitesattackthelarvaeofthebandedsunflowermoth.
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Figure 22. Banded sunflower moth adults are characterized by the dark band along the middle of the back.
Figure 23. Larva go through 5 instars and feed on the developing kernel within the seed.
Figure 24. Banded sunflower moth larva create a webbing on the face of sunflower heads.
The Sunflower Production Guide
Samplingstrategiesbasedonscoutingforadultmothsduringdaylighthoursandforeggshavealsobeendeveloped.
Economic Threshold
Ifmonitoringintheearlyeveningorearlymorning,onebandedsunflowermothpertwoplantsisareasonableeconomicthreshold.
NOTE:TheArthur’ssunflowermoth(Cochylis arthuri)isverysimilartothebandedsunflowermoth.TheArthur’ssunflowermothlarvaealsofedondevelopingseedsinthesunflowerheadcausingsimilardamagetothatofthebandedsunflowermoth.Theadultsalsohavedarkbandingacrossthewings,althoughtheycanbedistinguishedfrombandedsunflowermoth.Younglarvaearecreamcolored,mid-instarlarvaearelighttodarkpink,andlast-(fifth-)instarlarvaearelighttodarkgreen.
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The Sunflower Production Guide
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Lygus Bug
Feedingbylygusbugsondevelopingseedscancausekernelbrownspot,smallbrowntoblackspotsonthebluntordistalendofsunflowerseeds.
Host Crops
Lygusbugshavebeenrecordedonover385cropandweedspecies.
Biology
Adultlygusbugs(Figure25)areabout5mm(0.2inch)longand2.5mm(0.1 inch)wide.Theyvaryincolorfrompalegreentoreddish-brownandhaveadistincttriangleor“V”markonthewings.Firststagenymphsareverysmall,winglessandbrightgreen.Nymphs(Figure26)maylooksimilartoaphidsbutaremuchmoremobile.
Lygusbugsfeedonplantsbyinjectingplanttissuewithdigestiveenzymes,andthenextractingnutrientswiththeirneedle-likemouthparts.Lygusbugfeedingondevelopingsunflowerseedscancausescarringontheseeds,knownaskernelbrownspot.Whilebrownspotisnotknowntoaffectyield,thisqualityissuecanbesignificantinconfectionsunflowersbecauseprocessorsareonlyallowed0.5%damageinthefinishedproduct.Lygusbugfeedingcanalsoresultinabittertastetotheseeds.Whilebrownspotisvisibleondehulledkernels,thereisusuallynosignontheexteriorofthehullthatthekernelhasbrownspot.
Lygusbugsaremobileandcanbefoundonmanycrops.Lygusbugsprobablymovetosunflowersfromalfalfa,canolaorotherhostcropswhenthosecropshaveeitherbeenharvestedorsenesced.
Scouting Techniques
Scoutforadultsornymphsonthesunflowerheadsorfoliage.
Economic Thresholds
Lygusbugsarecapableofdamaging30to35seedsperheadperadult.Withtheindustrystandardallowingforamaximumof0.5%kernelbrownspot,theeconomicthresholdforlygusbugsonsunflowersislikelyabout1lygusbugper9heads.
Inresearchtrials,damagetosunflowerheadswasapproximatelytwiceasseverewheninfestationsoccurredatlatebudandearlybloomcomparedtostageswhenheadshadcompletedflowering.Thus,lygusbugmanagementshouldbeinitiatedpriortooratthebeginningoffloweringifadultdensitiesapproachtheeconomicthreshold.Fieldsshouldbemonitoredforlygusbugsuntilfloweringiscompletedtoreduceincidenceofkernelbrownspotdamageto confectionsunflowers.
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The Sunflower Production Guide
CONTROL TIPS
InsecticideapplicationismostbeneficialwhenappliedduringearlyfloweringattheR5.1stage.AsecondapplicationmaybewarrantedifLygusbugpopulationsarehighinneighboringfields,andpopulationsareexpectedtomigratetothesunflowerfield.ConsultthecurrentGuidetoCropProtectionforregisteredinsecticides.
Figure 25. Adult lygus bugs are characterized by a triangle across the wings.
Figure 26. Lygus bug nymphs resemble the adults but lack wings.
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The Sunflower Production Guide
BENEFICIAL INSECTS
34|Insects
Minute Pirate Bug
Bothnymphsandadultsfeedonavarietyofsunflowerpestsincludingaphidsandtheeggsandlarvaeofbandedsunflowermoth.
Green Lacewing
Adultsfeedonaphidhoneydew,plantpollenandplantnectar.
Green Lacewing Larvae
Predatortoavarietyofsunflowerpestsincludingaphids,sunflowerbeetleeggsandlarvae,andbandedsunflowermotheggsandlarvae.
Lady Beetles
Consumesunflowerbeetleeggs,aphids,andbandedsunflowermotheggsandlarvae.
Lady Beetles Larvae Damsel Bugs
Preyonsunflowerbeetlelarvae,andbandedsunflowermotheggsandlarvae.
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Two-Spotted Stink Bug
Preyonsunflowerbeetlelarvae.
Parasitic Wasps
Attackboththeeggsandyounglarvae ofbandedsunflowermoth,sunflowerseedweevilsandsunflowerstemweevils.
Ground Beetles (Carabid Beetles)
Candestroy40percentofoverwinteringlarvaeandpupaeofsunflowerbeetles.
Hover Fly
Increasescropyieldbyenhancingpollination.Feedson aphids.
Honey Bee
Increaseyieldinsunflowerbyenhancingpollination.
The Sunflower Production Guide
Pollination
Unlikenativesunflowers,currenthybridshavebeenselectedforandpossesshighlevelsofself-compatibility.Althoughself-compatiblesunflowerhybridsusuallyout-produceself-incompatiblecultivars,modernhybridscontinuetobenefitfrominsectpollination.Studieshaveshownthatinmostsunflowerhybridsseedset,yieldandoilquantityisincreasedwhenpollinators(suchasbees)arepresent.
Toachievemaximumyieldsandquality,oftentheuseofinsecticideisrequiredtoprotectthecropfrominsectcompetitors.Unfortunately,manyofthemajorinsectpestsofsunflowerattackthecropduringfloweringandinsecticideapplicationsharmthepollinatingbees.Belowaresomekeystrategiesthatcanhelpprotectthepollinators.
Key strategies:
� Scoutfieldsandapplyinsecticideonlywhenneeded.� ApplyInsecticideintheevening-Honeybeesareforagingwhenthesunis
upandduringthewarmerpartsofthedayandreturntothehiveatnight.Whenthebeesreturntothefieldthenextday,theeffectonthebeeswillbesignificantlyreduced.
� Lessharmfultobeesdoesnotnecessarilymeanlessharmfultopests–Thisisduetotherepellenteffectonbeesfromtheresidueofsomeinsecticides.Selectinsecticidesthatprovideeffectivecontrolofthetargetedpestswhileminimizingimpactonbees.
� Communicatewithbeekeepers–Contactingthebeekeeperaboutaninsecticideapplication,theinsecticidechosen,andthestepstakentoreduceharmtopollinators,helpsthebeekeepertodecideifadditionalmeasuresshouldbetakentominimizebeedamage.
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