What is the cause of conifer die off?  The root cause of die off is moisture stress.  Trees weakened by drought are most often attacked and killed by native insects or diseases.

Ponderosa pines killed by western pine beetle and Ips, Lake County. By D. Owen, Cal Fire.

Can insect-related tree mortality be prevented from spreading?  Area-wide treatments to prevent additional mortality are very difficult when trees are under severe stress and  insect populations are high. Treatments to protect individual trees have the highest probability of success.

If a tree is half dead, can it be saved?  In some instances, trees can die in part and still recover.  However, these trees have a higher probability of dying when drought persists as they are under increased stress. It takes time for the foliage of a dead tree to change color, so it is possible for a tree to appear to be half alive, but actually be dead.   Carefully monitor these trees for signs or symptoms of overall decline.    

Will more rain or watering help distressed trees?  It will help, but it is difficult to say how soon and how much it will help.  Drought-related tree mortality continues beyond the end of a drought because precipitation benefits are not immediate.  It takes time for trees to recover and for beetle populations to decline. Providing supplemental water to individual trees has been recommended, but there is little scientific guidance on how to do this.  Different tree species also have very different watering requirements. 

If we don't remove the already dying trees, will the rest be lost?  Beetles that kill trees can fly long distances, which makes area-wide control of beetle populations difficult.  To confound the issue, it is difficult to identify and remove beetle-infested trees before the beetles have left the tree.  If a tree's foliage has turned red-brown, many, if not most, beetles will have already emerged, moving onto other trees.  Removing such trees will have little impact on the beetle population.

Is bug-damaged wood good for high-end sale?  Wood from beetle-killed trees typically has lower value than wood from a tree that was alive when cut. Wood from such a tree may have staining or even insects, which can limit its marketability.