If you got that much damage from the beetles AFTER storing it in your shed with wood floors, I'd be seriously worried about the integrity of the shed itself....Think those turning blocks you have in the shed or barn are safe? Took this maple burl off the wood floor of me garage lean-to shed. Totally destroyed, it's just like powder on the inside!
Come and get it! Good luck when some more eggs hatch.Looks good to me! I'd stabilize it and turn it! Of course, I'm nuts....
What you are describing is the exit hole of the mature beetle. There are 3 stages, egg, larvae, and mature beetle. When the mature beetle bores out, it mates and starts the entire process all over again. There is absolutely no doubt this is what the PPB does inside the wood. If you still don't believe me, maybe you will believe the University of Kentucky. https://entomology.ca.uky.edu/ef650I can't tell you which particular beetle grub makes this kind of tracks, but these are not from powder post beetles. They leave tiny, like ball point pen type sized holes, and piles of powder. This is a boring grub. You can stabilize the frass/grub poop with thin CA glue. The other alternative is to use dental picks to pry it all out. You can also pressure wash a lot of it out. I don't think a water pick would be enough to get the frass out.
robo hippy