[ktrain]

Here is another item that is supposed to help with ambrosia beetles/ borers.
It doesn't seem 100%, and I believe you have to reapply after rains.
If they do happen to get your tree...I used this in full concentration with a syringe to shoot into the holes.
It did seem to work.

[Figless]

@ktrain took a look at this insecticide for borers and Ambrosia beetles. As you suggested it's a great solution for a nasty problem in your home Orchard. 7.9% Bifenthrin. Is a pretty strong pyrethroid that I have seen used in some 90 day Orchard pesticide Solutions that are rated 90 days. I guess if it rains you have to reapply another great suggestion Kevin well this one is not organic it is fundamentally a pyrethroid and should be safe to use on fruit trees. I definitely would use this product.