A. Prevention is the best method for managing borers in trees, says UC master gardener Janine Jacobs. Boring insects attack trees that are under stress due to other problems. Once attacked, there is little you can do for the tree other than pruning out the infested limbs. To determine which parts are actually infested, look for holes in the bark, stains, oozing liquid or sawdust-like deposits. Dispose of the removed branches.
Borers can migrate.
Do not save the wood for your fireplace or shred for mulch. Chemical injections of insecticide have not proven to be effective in control of borers, so save your money. Healthy, vigorous trees are rarely infested. Let us hear from you.