The egg laying is the start, and I believe that is always above ground. You could secure nylon screen around the base of the tree with rubber electrical tape and likely stop that, but a strong dose of properly timed Sevin would also do the trick. Just spraying the base of the trees with it may not be organic, but it certainly isn’t very environmentally disruptive or capable of entering the fruit.
The ashes idea is interesting, but doubtful to me. Old anecdotal solutions that really work don’t tend to stay in the previous century. Where there is ample rain it also would quickly drive up the pH well beyond the pile, I would assume. 5 gallons is quite a bit of ashes.
Just my opinion- maybe they do work. I’d like a member here with a real borer problem to try it and get back to us after a decade- one with at least a dozen peach and nectarine trees.
I thought the wood ashes I piled at the base of the peaches was detering them but the larva that enters the tree from the soil moved through that barrier apparently and have practically girdled six to eight inch tree trunks at the base…if they are caught early, (watch for a gell oozing at the base of the tree trunk)…there is some hope of limiting the damage by inserting a flexable wire into the tunnel until you are able to squish the invader.
My oldest peach trees were planted in 2018 so I’ve not had a lot of years worth of observation yet. I have raked away the previous ash layer and applied ~5gal of fresh wood ash per tree every year except for 1. I never got around to it that year (2 years ago I think), leaving the previous year’s ash there for a 2nd year. That fall I noticed frass and dug around and discovered quite the infestation of borers. Got those taken care of and applied fresh ashes and knock on wood, no tell-tales so far.
I was hopeful the alkalinity of the ash wouldn’t be a problem since:
Ashes may or may not help, I make zero claims… I just have an ample supply of it, soil pH seems agreeable, and it was recommended to me by someone who had grown peach trees for longer than I’ve been alive. They said it prevented borers and that seemed to mesh with my desire to prefer “natural” solutions over man-made “chemicals”. Stressing the word prefer in that, if it proves to not be effective I’ll go as nuclear as is necessary.
Worth noting that I spray my trees 5 or more times per growing season and somewhat follow Michael Philips “holistic” program. So Neem is being sprayed directly onto the trunk, but at far less concentration than I’ve seen you describe doing on your trees Scott.
