Beech, or birch? I know the latter can be really nice as a tonewood, never heard about the former being used in that context - and I often confound the two myself...
I mentioned xylphene; we treat just about any kind of wood object (not instruments) of unsure provenance with that. You apply it lavishly with a brush and then let the object in a well-ventilated place for a certain time. Apply a 2nd time for thicker objects. Sealing in plastic would make it more effective I suppose. I don't know exactly how wood occupants are killed by it, but it seems to work. It darkens the wood a little bit but doesn't penetrate very deep (not more than standard wood stain I'd say).
I see that's apparently a brand name for the French market -
https://www.xylophene.fr/ -
Xylophene | Lacrilar . I have to assume it is available elsewhere too, under different names.
I know there are also products you apply directly into the holes you find, via syringes. In fact, I'm pretty certain that even nitrocellulose laquer diluted with the appropriate thinner will be lethal for any insect larva living off your wood, but with this kind of DIY solution you'll probably want to make sure you've flooded the entire gallery system.
Benedetto 16-B Opulent Brown for sale
Today, 08:16 AM in For Sale