Organic Solutions for Tomato Hornworms

A Factsheet from Toxic Free NC

AboutTomatoHornwormsThetomatohornwormandtherelatedtobaccohornwormarepestsofthe“nightshades,”orSolonaceaefamilyofplants.Theseincludepotatoes,tomatoes,eggplants,peppers,toma<llos,tobacco,andpetunias.Tomatoesaretheirfavoritestoa>ack,buttheymayalsoa>acktheotherplantsinthisfamily.Hornwormsarethecaterpillarsofaspeciesofsphinxmoth,butonlythecaterpillarsdamagecrops.Theyeatleaves,stems,andfruitsoftheplants,whichcanhurtorevenkilltheplant.It’srarethathornwormscouldcompletelykillyourcrop,althoughdamageonindividualplantscanbeserious.The<psbelowaremeanttohelpyoukeephornwormsundercontrol.Sustainablepestmanagementstrategiesusuallyworkbestwhenusedtogether.Thinkaboutyourgarden,yourresources,andyour<me,andputseveralofthese<pstogetherintoaplanthatworksforyou.Iden2fyingTomatoHornwormsAdultsphinxmothsarelarge,dullbrownhoveringmothswiththickbodies.Theymaybeseenhoveringaroundflowersnearduskandareeasytomistakeforhummingbirds.The<nyyellowishovaleggsarelaidaloneorinsmallgroups.Thehornwormcaterpillarstartsoutsmallandyellowish-white,butquicklygrowsto3.5-4”longandaboutasthickaroundasyourthumb.TheyarepalegreenwithwhitediagonalorV-shapedmarkingsalongtheirsidesandablackorred“horn”s<ckingupfromtheirrear.Whenthey’vebeenmunchingonplants,theyleavebehindround,darkgreenfrass.Hornwormswhichhavebeena>ackedbyparasi<cwaspshavewhitecocoonsontheirbacksthatlooklikerice–don’tkillthose!Youmightevenwanttomovethemtoashelteredspottoprotectthem.Parasi<cwaspswillsooncomeoutofthosecocoonstokillmorehornworms,andthat’saverygoodthing.

Tomatohornworm.Photocredit:SturgisMcKeever,GeorgiaSouthernUniversity

AdultSphinxmoth.Photocredit:R.J.ReynoldsTobaccoCompanySlideSet,R.J.

ReynoldsTobaccoCompany

LifeCycleAdultmothscomeoutofthesoilinJuneandJulyaYerspendingthewinteraspupae.Theylaytheireggsontheleavesofplantsinthe“nightshade”family,andtheyounghornwormshatchinabout7days.Theyeatforthreeweekstoamonth,growingrapidly,beforediggingbackintothesoiltopupate.Thereareatleasttwogenera<onseachyearinNorthCarolina.Preven2on1)Growhealthyorganicplants.Strongtomatoplantsarebe>erabletohandlesomedamagefromhornwormsthanweak,strugglingplants.Makesurethatyourtomatoesarege\ngenoughsunandwater,andthattheirsoiliswell-drained,richinnutrients,andhasplentyoforganicma>er.2)Tillinthefall.Tillingthesoilinthefallcankillasmanyas90%ofthehornwormslivinginthesoil,sofarfewerhornwormswillcomeouttoeatandbreedinyourgardenthenextyear.GeFngRidofTomatoHornwormsWithoutToxicChemicals1)Scoutandhandpick.Handpickingisbyfartheeasiestandmosteffec<vemethodformanaginghornwormsinasmallgarden.Findingthemcanbehardsincethewormsarethesamecolorastheplants.Lookforleaveseatendowntothecentralvein,chewedfruit,orthedarkgreen,rounddroppings.HornwormsoYenhidealongtheleafstemswhentheyarenotfeeding,sotofindthemjustfollowthestemwithyoureyeawayfromthedamagedarea.Whenyoufindthem,simplycrushthem,dropthemintoapailofsoapywater,orsniptheminhalfwithscissors.Butifyoufindahornwormcoveredinsmallwhitecocoonsthatlooklikegrainsofrice,don’tkillit!See#4tofindoutwhy.

Tomatohornwormfrass.Photocredit:WhitneyCranshaw,ColoradoStateUniversity

Parasi2zedtomatohornworm.Photocredit:ClemsonUniversity-USDACoopera<veExtension

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2)AKractnaturalenemies.Youcana>ractparasitesandpredatorsofthetomatohornwormtoyourgardenbycrea<nghomesforbeneficialinsectsandotherhelpfulcreatures.Lacewingsandladybugs,bothofwhicheathornwormeggsandyoungcaterpillars,willmakeahomeinherbandflowerbedsandsmallshrubsnearthegarden.Afiercehornwormkilleristheparasi<cbraconidwaspwhichcanbea>ractedbypollenandnectarplantswithsmallflowers,suchaswildflowersandherbs.Thesewaspslaytheireggsdirectlyontomatohornworms.Whentheeggshatch,thelarvaedigintothehornwormandeatitfromtheinsideout.Theythencomebackouttopupateinsmallwhitecocoonsonthehornworm’sbackthatlooklikegrainsofrice.Thehornwormiskilledintheprocess.Whenthecocoonshatch,thenewadultwaspsflyawaytoa>ackotherhornworms.Soifyoufindahornwormwiththesecocoonsonitsback,leaveitalone!Be>eryet,moveittoaprotectedplaceinthegardenasanurseryforyourfriendstheparasi<cwasps!

Thisfactsheetwaswri-enwiththeneedsofnon-commercialhome,schoolandcommunitygardenersinmind.Cer:fiedOrganicgrowers,orthoseseekingacer:fica:on,shouldcheckwiththeircer:fyingagencybeforeusingANYinsec:cide.Someorganicallyacceptableinsec:cidesareapprovedforuseinCer:fiedOrganicsystemsonlyagainstcertainpestsorincertainsitua:ons.

4)Releasepredators.Ladybeetles,parasi<cwasps,aphidmidges,andlacewingscanalsobepurchasedandreleasedintothegarden.Lookforthemingardeningandseedcatalogs.5)Bioinsec2cideBTK.BTK(Bacillusthuringiensis,var.kurstaki)isatypeofbacteria.Wheneatenbythehornworm,BTKmakesapoisoninthecaterpillar’sgut.Thepestwillstopea<ngandeventuallydie.BTKispartlyselec<ve,meaningitwillkillmanycaterpillarpestsbutisn’tharmfultomostothercreatures.However,BTKcanalsokillthecaterpillarsoffriendlybu>erfliesandmoths,souseitcarefully.Itmustbeeatenbythehornwormstowork,sosprayitontheleavesofyourplantswhereyouseehornwormdamage.Itiseasilywashedaway,soitshouldbereappliedaYeraheavyrain.TofindBTK,checkgardeningandseedcatalogs.MakesuretochecktheBTKproductyouselectontheOrganicMaterialsReviewIns<tute’slistofproductsapprovedforcer<fiedorganicfarmstoavoidanytoxicingredients.BTKcanbeexpensive,andsincehandpickingandnaturalenemiescanworksowellforhornworms,BTKshouldonlybeusedasalastresort.Forthesamereasons,otherinsec<cidesarenotrecommendedforhornwormcontrol.

SourcesEllis,BarbaraandBradley,FernMarshall,editors.TheOrganicGardener'sHandbookofNaturalInsectandDiseaseControl:ACompleteProblem-SolvingGuidetoKeepingYourGardenandYardHealthyWithoutChemicals.RodalePress,1996.Flint,MaryLouise.PestsoftheGardenandSmallFarm:AGrower'sGuidetoUsingLessPes<cide,2ndEdi<on.UniversityofCaliforniaPress,1998.Wold-Burkness,S.J.andHutchison,W.D.“TomatoHornworm.”UniversityofMinnesota:VegEdge–VegetableIPMResourcefortheMidwest.ViewedMarch,2012:[link]“Hornworms.”Insectandrelatedpestsofvegetables.NorthCarolinaStateUniversity:CenterforIntegratedPestManagement.ViewedMarch,2012:[link]