Organic Solutions for Tomato Hornworms

Organic Solutions for Tomato Hornworms
A Factsheet from Toxic Free NC
AboutTomatoHornworms
Thetomatohornwormandtherelatedtobaccohornworm
arepestsofthe“nightshades,”orSolonaceaefamilyof
plants.Theseincludepotatoes,tomatoes,eggplants,
peppers,toma<llos,tobacco,andpetunias.Tomatoesare
theirfavoritestoa>ack,buttheymayalsoa>acktheother
plantsinthisfamily.
Hornwormsarethecaterpillarsofaspeciesofsphinxmoth,
butonlythecaterpillarsdamagecrops.Theyeatleaves,
stems,andfruitsoftheplants,whichcanhurtorevenkillthe
plant.
It’srarethathornwormscouldcompletelykillyourcrop,
althoughdamageonindividualplantscanbeserious.The
<psbelowaremeanttohelpyoukeephornwormsunder
control.Sustainablepestmanagementstrategiesusually
workbestwhenusedtogether.Thinkaboutyourgarden,
yourresources,andyour<me,andputseveralofthese<ps
togetherintoaplanthatworksforyou.
Tomatohornworm.
Photocredit:SturgisMcKeever,GeorgiaSouthernUniversity
Iden2fyingTomatoHornworms
Adultsphinxmothsarelarge,dullbrownhoveringmoths
withthickbodies.Theymaybeseenhoveringaroundflowers
nearduskandareeasytomistakeforhummingbirds.The
<nyyellowishovaleggsarelaidaloneorinsmallgroups.
Thehornwormcaterpillarstartsoutsmallandyellowishwhite,butquicklygrowsto3.5-4”longandaboutasthick
aroundasyourthumb.Theyarepalegreenwithwhite
diagonalorV-shapedmarkingsalongtheirsidesandablack
orred“horn”s<ckingupfromtheirrear.Whenthey’vebeen
munchingonplants,theyleavebehindround,darkgreen
frass.
Hornwormswhichhavebeena>ackedbyparasi<cwasps
havewhitecocoonsontheirbacksthatlooklikerice–don’t
killthose!Youmightevenwanttomovethemtoasheltered
AdultSphinxmoth.
Photocredit:R.J.ReynoldsTobaccoCompanySlideSet,R.J.
spottoprotectthem.Parasi<cwaspswillsooncomeoutof
ReynoldsTobaccoCompany
thosecocoonstokillmorehornworms,andthat’savery
goodthing.
LifeCycle
AdultmothscomeoutofthesoilinJuneandJulyaYer
spendingthewinteraspupae.Theylaytheireggsonthe
leavesofplantsinthe“nightshade”family,andtheyoung
hornwormshatchinabout7days.Theyeatforthreeweeks
toamonth,growingrapidly,beforediggingbackintothesoil
topupate.Thereareatleasttwogenera<onseachyearin
NorthCarolina.
Preven2on
1)Growhealthyorganicplants.Strongtomatoplantsare
be>erabletohandlesomedamagefromhornwormsthan
weak,strugglingplants.Makesurethatyourtomatoesare
ge\ngenoughsunandwater,andthattheirsoiliswelldrained,richinnutrients,andhasplentyoforganicma>er.
2)Tillinthefall.Tillingthesoilinthefallcankillasmanyas
90%ofthehornwormslivinginthesoil,sofarfewer
hornwormswillcomeouttoeatandbreedinyourgarden
thenextyear.
Tomatohornwormfrass.
Photocredit:WhitneyCranshaw,ColoradoStateUniversity
GeFngRidofTomatoHornwormsWithoutToxic
Chemicals
1)Scoutandhandpick.Handpickingisbyfartheeasiestand
mosteffec<vemethodformanaginghornwormsinasmall
garden.Findingthemcanbehardsincethewormsarethe
samecolorastheplants.Lookforleaveseatendowntothe
centralvein,chewedfruit,orthedarkgreen,round
droppings.
HornwormsoYenhidealongtheleafstemswhentheyare
notfeeding,sotofindthemjustfollowthestemwithyour
eyeawayfromthedamagedarea.Whenyoufindthem,
simplycrushthem,dropthemintoapailofsoapywater,or
Parasi2zedtomatohornworm.
sniptheminhalfwithscissors.Butifyoufindahornworm
coveredinsmallwhitecocoonsthatlooklikegrainsofrice, Photocredit:ClemsonUniversity-USDACoopera<veExtension
SlideSeries
don’tkillit!See#4tofindoutwhy.
2)AKractnaturalenemies.Youcana>ractparasitesandpredatorsofthetomatohornwormtoyourgardenbycrea<ng
homesforbeneficialinsectsandotherhelpfulcreatures.Lacewingsandladybugs,bothofwhicheathornwormeggsand
youngcaterpillars,willmakeahomeinherbandflowerbedsandsmallshrubsnearthegarden.
Afiercehornwormkilleristheparasi<cbraconidwaspwhichcanbea>ractedbypollenandnectarplantswithsmall
flowers,suchaswildflowersandherbs.Thesewaspslaytheireggsdirectlyontomatohornworms.Whentheeggshatch,
thelarvaedigintothehornwormandeatitfromtheinsideout.Theythencomebackouttopupateinsmallwhite
cocoonsonthehornworm’sbackthatlooklikegrainsofrice.Thehornwormiskilledintheprocess.Whenthecocoons
hatch,thenewadultwaspsflyawaytoa>ackotherhornworms.Soifyoufindahornwormwiththesecocoonsonits
back,leaveitalone!Be>eryet,moveittoaprotectedplaceinthegardenasanurseryforyourfriendstheparasi<c
wasps!
4)Releasepredators.Ladybeetles,parasi<cwasps,aphidmidges,andlacewingscanalsobepurchasedandreleased
intothegarden.Lookforthemingardeningandseedcatalogs.
5)Bioinsec2cideBTK.BTK(Bacillusthuringiensis,var.kurstaki)isatypeofbacteria.Wheneatenbythehornworm,BTK
makesapoisoninthecaterpillar’sgut.Thepestwillstopea<ngandeventuallydie.BTKispartlyselec<ve,meaningit
willkillmanycaterpillarpestsbutisn’tharmfultomostothercreatures.However,BTKcanalsokillthecaterpillarsof
friendlybu>erfliesandmoths,souseitcarefully.Itmustbeeatenbythehornwormstowork,sosprayitontheleaves
ofyourplantswhereyouseehornwormdamage.Itiseasilywashedaway,soitshouldbereappliedaYeraheavyrain.
TofindBTK,checkgardeningandseedcatalogs.MakesuretochecktheBTKproductyouselectontheOrganic
MaterialsReviewIns<tute’slistofproductsapprovedforcer<fiedorganicfarmstoavoidanytoxicingredients.BTKcan
beexpensive,andsincehandpickingandnaturalenemiescanworksowellforhornworms,BTKshouldonlybeusedas
alastresort.Forthesamereasons,otherinsec<cidesarenotrecommendedforhornwormcontrol.
Sources
Ellis,BarbaraandBradley,FernMarshall,editors.TheOrganicGardener'sHandbookofNaturalInsectandDisease
Control:ACompleteProblem-SolvingGuidetoKeepingYourGardenandYardHealthyWithoutChemicals.Rodale
Press,1996.
Flint,MaryLouise.PestsoftheGardenandSmallFarm:AGrower'sGuidetoUsingLessPes<cide,2ndEdi<on.
UniversityofCaliforniaPress,1998.
Wold-Burkness,S.J.andHutchison,W.D.“TomatoHornworm.”UniversityofMinnesota:VegEdge–VegetableIPM
ResourcefortheMidwest.ViewedMarch,2012:[link]
“Hornworms.”Insectandrelatedpestsofvegetables.NorthCarolinaStateUniversity:CenterforIntegratedPest
Management.ViewedMarch,2012:[link]
Thisfactsheetwaswri-enwiththeneedsofnon-commercialhome,schoolandcommunitygardenersin
mind.Cer:fiedOrganicgrowers,orthoseseekingacer:fica:on,shouldcheckwiththeircer:fyingagency
beforeusingANYinsec:cide.Someorganicallyacceptableinsec:cidesareapprovedforuseinCer:fied
Organicsystemsonlyagainstcertainpestsorincertainsitua:ons.