handy, have you confirmed that it’s termites chompin’ yer domicile and not some other wood destroying insect? Ya gotta know yer enemy before you plan a strategy of attack.
That said, are there any physical signs of an infestation? Mud tubes? Small brown pellets? Any sawdust-type residue? Small circular emergence holes?
Alas, since I’m trained only in northeast sector bugs, I only know from them. Formosan termites and drywood termites aren’t this far north.
But I’ll give it my best shot, and maybe you can do some scouting around. BTW, the internet is great in this regard. Lots of universities have websites and if they have entomology depts you can find a lot of useful info without feeling like they’re trying to sell you something. Check it out.
Anyway, here are some symptoms and their related pests:
You’re right that termites aren’t real gung-ho on redwood and cedar. Not that they’ll avoid them like the plague, but they’ll utilize another food source first. I don’t know about formosans, but eastern subs leave mud tubes on exposed surfaces such as foundation walls or basement/garage slabs. If you find a mud tube and break it open, you might actually see the little white buggers traipsing around. Formosan colonies are larger, and more aggressive feeders. And for all I know, they may not mind redwood as much as the eastern subs.
Drywood termites actually nest in the wood (people have bought furniture that’s already infested with drywoods). They leave small, oblong fecal pellets, beige in color. If you see any of these, think drywood termites. Again, I don’t know about their feelings on redwood.
Powder post beetles get into trees before they’re milled, lay eggs in the grain and then the larvae hatch and eat their way out, leaving tiny round emergence holes and a powdery residue. I’ve seen them in the fir used in framing and in oak floors, so they may not discriminate much as to flavor.
Carpenter ants I assume you can figure out for yourself. If you’re seeing huge black ants parading all around, that’s them. And they leave a coarse wood residue that may also contain body parts. When they clean house, they clean everything, even the dead guys.
I wish I could be more helpful, handy, but there aren’t a heckuva lotta redwoods in southeastern New York.
Two final suggestions, 1) do a search on “termites” (the University of Toronto has an informative site, IIRC) and 2) call a reputable company and ask for an inspection. Usually they’re free. Then at least you’ll know what you’re up against from someone who has seen firsthand and also knows the critters in your neck of the woods (so to speak).