The sawyer beetles (genus Monochamus) are secondary insects. They prefer weakened or recently dead trees. It is probable that their population built up in the trunks of the damaged trees and now they are attacking the other live but probably weakened trees nearby. There should also be some smaller beetles - Ips - involved as well. Debarking the dead trees will prevent further egg-laying attacks, but it is likely those trees have probably been thoroughly colonized. If you have a good site for pine, the beetle population cannot sustain itself in vigorous trees.
If you want to be sure to reduce or eliminate the beetle population, and if it is not too big of a job, pile the dead trees, especially those that were attacked this year, and burn them over the winter to kill the eggs and larvae that will emerge next year. For more information see: Pine Sawyer Beetles.
