bring back........... DDT
I don't know if DDT will work on them. They live under the bark of the tree and bore their way into its core.
I don't know a whole lot about the issue, but I think it's because these bugs don't have any natural predators is why they are spreading so fast, combined with the mild winter temps along the coast which don't get cold enough to freeze and kill them off like it does further in the interior.
Bump