If you haven't yet sprayed the pine trees you don't want to sacrifice to the pine beetles, you had better hurry up and do it. There isn't anything you can do to save a tree that is already infested. That tree is pretty much doomed. But you can do something to protect the trees that are still healthy and green.
The rule of thumb is to spray twice during the warm months to protect your pines. SEVIN is a good all purpose pesticide, and you can buy it in concentrate form at Wal-Mart. Mark your calendar to remind yourself to spray around April Fool's and Fourth of July. Spray liberally from the bottom of the trunk up, and all the limbs as high up as you can reach.
If you have to clear and prune during the warm months, keep the spray tank handy so you can spray the pines, pinyon and ponderosa, you are trimming, as well as the surrounding pines. You need to get rid of the downed wood and slash as quickly as possible. Beetles are attracted to the odor of sap like bears to honey. Last year, yours truly lost about seven pinyons because I piled up slash and didn't get it chipped right away. Then I lost another tree because I disposed of the chips in a depression near the base of that tree. This year I'm spraying all slash piles, as well as the chips.
As long as this drought continues, our ponderosas and pinyons will be weakened and many will be unable to muster up the pitch needed to repel the beetles as they bore into the tree. Normal healthy trees are able to secrete resin when the beetles begin to enter the tree, and they literally "pitch" them out.
As soon as you notice any trees that are turning brown, it's best to cut them down, and segregate the wood in a sunny place well away from healthy pines. You can kill the beetles in the wood by soaking the wood with water, then covering the pile with plastic. This will create a hot, steamy environment that will parboil the little buggers. You can also use diesel fuel minus the plastic. All slash needs to be disposed of if you don't want it to incubate a new crop of beetles.
If you don't feel you can spray your entire forest, you probably do want to spray the trees close to your house. When you have a big tree next to the house die, it's a pretty touchy process cutting it down without destroying your house. It's far safer to spray in the first place.
For more detail on pine beetles, use the following links to previous articles on this subject.
Pine Beetle Season
Fighting the Pine Beetle
Attack of the Pine Beetles