Posted: Thu Mar 16, 2006 7:24 pm Post subject: Twig borer eats almond nutlets
Every year I learn something I should have known before.
I observed twig borer larvae chewing on nutlets in almonds (March 14). Each larvae had destroyed 2-3 nutlets. The larvae I saw were near full grown, but I suppose there are other smaller larvae just getting started. I'm guessing they will move to shoots once growth gets moving.
This is in an orchard of hard-shelled nuts, where I have not been particularly concerned with twig borer.
I don't feel too bad not knowing this. The UC IPM manual and the website do not mention feeding on the young nuts.
Devin Carroll
Posted: Thu Mar 16, 2006 7:29 pm Post subject: Coviello photo
Hi Devin, I have a reasonably decent photo of a mature, overwintering larva feeding on a flower bud, which I've used in a few meetings. From a twig borer's point of view, it doesn't seem to make any difference whether it's a vegetative bud or a fruit bud, or even if it's already pollinated; it's fresh growing tissue, which is a comparatively rare commodity in late winter and early spring.
Rich
Richard Coviello, Farm Advisor, Emeritus
University of California Cooperative Extension
1720 S. Maple Ave.
Fresno, CA 93702
(559) 456-7549
Posted: Thu Mar 16, 2006 7:31 pm Post subject: Morgner - not very economic
Twig borer commonly feed on flower buds, flowers and small nuts when they emerge from the hibernaculum. Hard to say whether this is economic. My guess is it's not.
Damage to leaf buds and early shoots on 2nd leaf almonds is common and I have seen the upper 18" of scaffolds denuded from this feeding. It seems to hold the trees back a bit and every year I end up treating a few blocks for PTB larvae about this time...mid March. My treatment threshold is 25 to 30% damage.
Chris Morgner
Posted: Thu Mar 16, 2006 7:32 pm Post subject: Coviello agrees
I agree, Chris. I doubt that flower and nut feeding is going to have any significant impact on crop yield, and certainly not on quality because those nuts are going to fall off anyway. I, too, have seen feeding on 1-2 year old trees where PTB has taken out almost every bud on a scaffold. It seems to me that one would not want to lose very many of those new shoots, especially on 2 year old trees, because you're losing choices of how you want to shape the tree for future production. Your threshold sounds reasonable to me. Hope this is a good year for you
Rich