Lesser Peach Tree Borer

I have an infestation of lesser peach tree borers LPTB which I misdiagnosed this spring as bacterial canker, due to the gummosis in all the likely places -- cracks in the trunk, crotches of scaffold limbs and branches up to a height of about 4'. When I learned from talking with our extension agent in August that it was much more likely to be LPTB I sprayed all the cracks in the trunk and branches with Bt (his suggestion) and Neem oil (Michael's recommendation). Then I plastered the cracks with a clay slurry (Surround and water).

I hung a pheromone trap for LPTB on Sept 1 and caught 8 LPTB in 5 days. A few days ago I used an insecticide drench (Bt and Neem oil) on all the trunks and lower scaffolds.

From my research attempts it seems that the LPTB has 1-2 or 2-3 generations per year (depending on who you read) extending from May through September. So I apparently am in the midst of the second or third flight of the moths. The gum oozing from the cracks in May was caused by the emerging larva I assume.

Is the insecticide drench aimed at killing the moths when they land to lay eggs? Or the larva? How often do I need to repeat the insecticide drench -- every 4-5 days as long as I keep seeing more moths in the trap?

What is the clay slurry (again Michael's suggestion) trying to accomplish? What is the best strategy next spring?

Turkey Creek Orchard
Solon, Iowa (zone 5A)

Learning that "gummosis" is a prunus response to any injury has value, and now zeroing in on the actual cause means you will get on top of this, Peter. The fact that this borer is the larvae of a moth shifts a few of the thoughts with which we approach beetle grubs of the borer persuasion.

Bt has value if the borer larvae consume the moth-specific protein toxin. I doubt much will happen on that score, given the inner cambium feeding but a surface application ... but it doesn't hurt to try.

Neem oil impacts the molting cycle so you will eventually stop many larvae in their development and thus life cycle. The fats in neem are readily absorbed by bark tissues so the azadiractins (active insect constituents) will be in the cambium to act both by ingestion and on contact. Neem trunk sprays may deter the female moth from laying eggs but that timing has to be preemptive. Your situation is more like finding RHAB egg slits at the soil line, only LPTB works branch crotches. Spreading "neem butter" directly from the jug (literally with a butter knife) to damaged areas is an experimental idea which I'm finding very useful in my own borer battles.

The clay slurry works principally to confuse the crawling female beetle as she works her way down from the canopy to the soil line. This may not have much value with moths who fly into place. A clay coating (especially with a tad of latex paint as part of the slurry) also helps make grub damage more obvious.

The other thing to consider with moth borers is spinosad. Very expensive, yes, but it too works on contact as well as by ingestion. Just be sure to rotate approaches as we don't want any pest building up resistance to this spray.

Last fall I worked with a grower in Idaho with bad peach tree borer infestation. Same idea but this moth cousin concentrates its larval activity at the soil line. I suggested a neem soil drench. Here's what she reported back though it goes beyond what I understand about neem action:
I went ahead and used 70% Neem Oil since we had this on hand. We poured this full strength on the trunks of trees and saturated around base until it puddled. I checked our plum tree that is completely girdled with eggs again about 20 to 30 minutes after applying the NEEM oil and we found 12 ugly borers laying on the soil all around base of tree. So it is having some effect at least. I also saw some pop out from bottom of trunk right after pouring--amazing to watch.

Lost Nation Orchard
Zone 4b in New Hampshire



Edited 1 time(s). Last edit at 09/09/2015 06:58AM by Michael Phillips.

I am battling them again, with neem oil trunk spray and whitewash, in the midst of the first moth flight. But I am wondering if it is possible to trap them out in a small orchard like ours. We have about 30 bearing peach trees.

Turkey Creek Orchard
Solon, Iowa (zone 5A)

Parasitic nematodes.

Mike Biltonen, Know Your Roots
Zone 5b in New York