peachtree borer - extension
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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.
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(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.