So, I live near you, of course. That grub you posted is the BIG borer I mentioned. Usually found under 5he bark and in first ring or two of sapwood. These guys, and also the beetle borer (bronze birch bkrer, locust borer, mulberry borer, etc. ) types come to us as eggs under the bark. Removing bark and sealing with shellac will prevent these guys.
Terrible protein source if you ask me, but not half bad icefishing bait.
The other issue is those little tiny ones, which I assume are the powder post beetles. I have had them eat right through every type of finish, and removing bark won't prevent them.
They seem to like dry wood that has been sitting awhile. Heat treating white wood seems to invite them in, it's almost like they prefer it. I have had elm sit for two years with no issues, heat treat and straighten it (which would kill eggs and any existing larvae) and had it riddled with these small bores a month later. They seem to love to eat winter rings, as I have had them literally delaminated a bow for me before, between thick growth rings. Just popped in half. They also bore straight down into the face of prepped staves, leaving small holes like a pencil lead size.
The second kind is the type that comes in waves and suddenly a lot of my wood in unusable. They never touch black or yellow locust heartwood, but LOVE my plum, mulberry, elm, and ash.
If you can find a way to make them go away forever, I'll thank you.
Also, you seem up on this stuff, but ALWAYS be careful mixing chemicals. Aside from the active ingredients, the additives and stuff might give unexpected results.
I mention this because I have seen a good dozen people over the years come in to our ER having mixed various household chemicals and being overcome by fumes. One lady actually mixed bleach and ammonia while trying to kill ants.
