well i have that problem with pine beetles , not real bad, but like u said the larve eat the wood then develop into beetles, and come out,then goes to lay eggs i guess, they even were in some of my floor joist back in the 70s when the house was new, i think they were in the wood when it was cut, but where my mom worked came out and sprayed all my joist with some real powerfull stuff that was actually illegal to use, but had been used in the past, that got them, i could hear them at nite when working in the basement, i thought it was a mouse, , lol, but the tree needs to come down before they spread to other trees,this was before i bought the property beside me and behind me, the trees in my original yard are big and healthy, when mom use to could get me strong stuff free, i would spray the trees but mix it with diesel fuel as i was told to do,, but i dont spray them now, lightning got 3 trees, anyway, my trees work me to death, i have way to many, take care