From Wikipedia: Mountain Pine Beetle
The beetles kill the trees by boring through the bark into the phloem layer on which they feed and in which eggs are laid. Pioneer female beetles initiate attacks, and produce pheromones which attract other beetles and results in mass attack.
That’s what I understood as well. The beetles essentially “girdle” the tree under the bark.
A huge percentage of pinion pines between Tijeras and Taos have been killed. It seemed to stop about 8 miles north of my place a few years back, haven’t had any trees go yet. So far, it’s been very cold and we’ve gotten good moisture this winter.
Looked out into the yard through the -40 air and no Wikipedia was sighted and if they were the Troopers would be on the way.