Question
We have a vacation home/property in Montana that is experiencing problems with the douglas fir beetles.  We lost 8 last year to them and another 5 this year.  We have been treating the remaining trees with the pheromones.  Last year we removed several of the dead trees, but we are hesitant to remove many more because they are on a steep slope next to a lake.  We'd like to keep trees for wildlife and to help the stability of the slope.  Our neighbor feels we should remove any and all trees that have been attacked and killed by the beetles.  What is your take on the damaged/dead trees?  thanks!

Answer
There is a difference in trees that have been attacked and those that are dead from attack. After the tree dies and the beetles hace emerged then thios tree does not contain an active population of beetles and is not a threat in spreading the beetles. (no Doug fir beetles are present in the tree.) These trees can be cut or not depending on the location and the hazard of them hitting anything if they fall. Now the trees that have been attacked and still have Doug fir beetles in them are a threat as breeding grounds for future generations of beetles and increase the chance of the emerging beetles attacking the other nearby trees.
These trees need to be cut and removed from the site to reduce the beetle population.

Pheromones are usually used to bait trap trees to draw beetles into a tree and then this tree is cut and removes along with beetles in the tree thus cutting down on the population. Semiochemicals (message-bearing chemicals), emitted by the beetle and the host tree upon attack, regulate the behavior of beetles during their mating and aggregation phase. Certain elements of beetle-produced pheromones, when combined with specific host monoterpene odors, serve to guide additional flying beetles to the tree and ensure that they are concentrated in sufficient numbers to overcome resin defenses of the tree. The attractive ele-ments have been combined into a lure thatis effective in aggregating adult beetleswhen placed on suitable host trees. Concentrating attacking populations can make salvage or sanitation logging more effective.Other elements of this pheromone complex serve to disrupt aggregation and thereby ensure attack densities are optimum for brood survival. Release of this anti aggregating component also serves to divert responding beetles to nearby trees,resulting in the characteristic group-kill pattern. The anti aggregative component has been used experimentally to reduce the level of attack and survival in windthrown trees well below optimum levels. Its usefulness for protecting standing green trees has also been successfully tested. Use of synthetic pheromones for beetle suppression is subject to registration bythe Environmental Protection Agency. The Agency has determined that the aggregative pheromone applied to trees is exempt from registration. Registration of the antiaggrative component is pending. Field tests to measure the effective-ness of these synthetic pheromones and determine their most effective deployment are under way. Check with federal or state forest entomologists for current recommendations.
Instead of pheromones I would use a oreventive insecticide spray. The newest is an insecicide called onxy which will protect the tree from attack.
Since this is a complicated issue of the location of the trees, whether they contain an active brood of beetles, if the dead trees are a hazard and what to spray for prevention, I would recommend that you call the loacl state Forestry agency and ask one of their foresters to take a look and see what they recommend. Their number should be in the local phone book or here is a web link to their main office pest management contacts. They should be able to give you all the information needed.
http://dnrc.mt.gov/forestry/assistance/pests/default.asp