Fact Sheet No. 5.566 Insect Ser ies|Trees and Shrubs

Quick Facts•Peachtreeboreristhemostdestructiveinsectpestofpeach,cherry,plum,andotherstonefruitsinColorado.

•Damageisdonebytheimmaturelarvae,whichchewbeneaththebarkofthelowertrunkandlargerroots.

• Insecticidespraysappliedtothelowertrunkwheneggsarebeinglaidcanpreventnewinfestations.

Peachtreeborer(Synanthedon exitiosa)isthemostdestructiveinsectpestofpeach,cherry,plum,floweringplumandotherstonefruits(Prunus spp.)inColorado(Figure1).Thegrub-likelarvaechewunderneaththebarkatthebase(crown)ofthetreeandonlargerroots,habitsthatlenditanothercommonname“peachcrownborer”(Figure2).Thegougingwoundstheyproducecanbequiteextensiveandmayseriouslyweakenandevenkilltrees,butmaynotbeobviousunlesstheareaaroundthebaseofthetreeisexamined.Externalevidenceofpeachtreeborer

tunnelingisawetspotonthebarkorthepresenceofoozing,gummysap.Thesapisclearortranslucentandoftendarkfromthesawdust-likeexcrementoftheinsect.Mostinjuriesoccuralongthelowertrunkbeneaththesoilline.Lowerbranchesrarelyreceiveinjuries.(Note:Oozingwoundsonpeachthatproduceanamber-coloredgummaybecausedbycytosporacankerhttp://extension.colostate.edu/topic-areas/agriculture/cytospora-canker-in-tree-fruit-crops-2-953,acommonfungaldiseaseofstonefruitsthatproducessymptomsthatmaybemistakenforthoseproducedbypeachtreeborer.Thepresenceofsmallparticlesofwoodandbarkwithinthegumdistinguishdamagebypeachtreeborer.)

Life History and HabitsThelifecycleofthepeachtreeborer

requiresoneyeartocomplete.Onlytheimmature(larva)stage(Figure3)producesthedamagetotrees.Uponhatchingfromtheeggs(Figure4),younglarvaeimmediatelytunnelintothesapwoodofthetree,usuallythrough

by W.S. Cranshaw*

cracksandwoundsinthebark.Larvaecontinuetofeedanddevelopuntiltheonsetofcoldweather.Mostactivityoccursafewinchesbelowgroundonthetrunkandlargerroots.Theinsectsspendthewinteraspartiallygrownlarvaebelowgroundunderthebark.Withthereturnofwarmersoil

temperatureslarvaeresumefeedingandmostinjuryisproducedinmid-tolatespringasthelarvaemature.ThelarvaefinishfeedingandchangetothepupalstageinlateMaythroughearlyJuly.Pupationoccursinacellmadeofsilk,gumandchewedwoodfragments,locatedjustbelowthesoilsurface(Figure5).Theadultsemergewithinamonth

andintheprocessoftenwillpulloutthepupalskins,whichmaybethenbeseenaroundthebaseofthetrunk(Figure6).Adultsofthepeachtreeborer(Figures7,8)areatypeof“clearwingborer”moththatresemblewasps,buttheyareharmlessandincapableofstinging.Unlikemostmothspeachtreeborers

Peachtree Borer

*Colorado State University Extension entomologist and professor, bioagricultural sciences and pest management. 1/2018

FFigure 1. Gumming produced at the base of a tree due to wound by a peachtree borer larva. Photograph courtesy of James Solomon, USDA Forest Service

©ColoradoStateUniversityExtension.2/05.Revised1/18.

extension.colostate.edu

ColoradoStateUniversity,U.S.DepartmentofAgricultureandColoradocountiescooperating.CSUExtensionprogramsareavailabletoallwithoutdiscrimination.Noendorsementofproductsmentionedisintendednoriscriticismimpliedofproductsnotmentioned.

(andotherclearwingborers)flyduringthedaytime.Thefirstadults,males,mayemerge

inasearlyasmid-June.However,femalesusuallyfollowbyacoupleofweeksandmostadult activity–

Figure 4. Peachtree borer eggs. Photograph courtesy of Ken Gray Collection, Oregon State University

Figure 3. Peachtree borer larva in the base of a peach.

Figure 2. Peachtree borer larvae in roots of a peach. Photograph courtesy of Eugene Nelson, Colorado State University

matingandegglaying-occursduringJulyandAugust.Duringthistimethefemalemothslayeggsonthebarkofthelowertrunkandinsoilcracksnearthetreebase.Eggsgenerallyhatchinabout10days.

Preventive SpraysPeachtreeborerismosteasily

controlledbyspraysofinsecticidesappliedtothelowertrunkandbaseofthetree.Thesearepreventivespraysthattargettheeggsandearlylarvalstagesexposedonthebarkofthetree.Oncelarvaehavemigratedintothetree,insecticidesarenoteffective.Dependingonseasonal

temperaturesonecanexpectpeachtreeborertobeginlayingeggsinverylateJuneorearlyJuly.MostalleggswillbelaidduringJulyandAugust,althoughafewadultsmaystillbepresentintoSeptember.Awaytobestdeterminewhenadult

peachtreeborersarelocallyactiveisthroughuseoftraps.Variousdesignsoftraps,usuallywithastickybottom,areusedandallcaptureadultmales.Theseareluredintothetrapbyachemical(sexpheromone)thatmimicswhatfemalepeachtreeborersusetoattractmates(Figure9).Suchtrapscangiveoneanideaofwhenadultsarepresent,whichisassociatedwithperiodswheneggsarebeinglaid.Intheabsenceofusingthesetraps,

asageneralguideline,preventivetrunkspraysshouldbeappliedaroundthefirstweekofJuly.WherelargenumbersofpeachtreeborerscontinuetobeactivelaterinsummeritmaybeusefultomakeasecondapplicationinearlyAugust.

Figure 5. Pupa and pupal cocoon of a peachtree borer.

Figure 6. Pupal skins extruding from base of a tree after adult emergence. Photograph courtesy of David Shetlar, Ohio State University

Tobeeffectiveasapreventivespray,theinsecticidemusthavesomeresidualactivity,allowingittokillyoungpeachtreeborerlarvaeemergingfromeggsforseveralweeksafterapplication.Presentlycertainformulationscontainingtheactiveingredientspermethrin(Astro,Hi-Yield38,etc.)orcarbaryl(Sevin)aretheonlyinsecticidesthatcanlegallybeusedbackyardfruittrees,havereasonablygoodresidualactivityonbarkafterapplication,andarelabeledforcontrolofpeachtreeborer.

Figure 7. Peachtree borer, adult male.

Figure 8. Peachtree borer, adult female. Photograph courtesy of David Leatherman.

Figure 9. Peachtree borer males attracted to a trap baited with a sex pheromone lure.