Bugs in the System: Development of Tools to Minimize Ponderosa Pine Losses from Western Pine Beetle Infestations

The western pine beetle, Dendroctonus brevicomis LeConte, is a major cause of ponderosa pine, Pinus ponderosa Dougl. Ex Laws., mortality in the western USA and particularly in California. Under certain conditions, the beetle can aggressively attack and kill apparently healthy trees of all ages and size classes. The average loss is substantial, and has been estimated at 1 billion board feet annually. The availability of pest management techniques for preventing and suppressing infestations is rather limited. Currently, we are conducting several studies on the development of chemical, silvicultural and semiochemical-based management tactics for minimizing the negative impacts associated with D. brevicomis infestations. This paper describes the status of four such studies. Efficacy of the insecticide bifenthrin for protecting individual, high-value trees, and of the anti-aggregation pheromone verbenone for protecting small stands, is described. In a trapping bioaasay, nine nonhost angiosperm volatiles significantly augmented the effect of two release rates of verbenone, reducing trap catches to levels significantly below that of either release rate of verbenone alone. These results suggest that the addition of nonhost angiosperm volatiles to verbenone could be important for developing successful semiochemical-based management techniques for D. brevicomis. In another study, we examined and described the effect of mechanical fuel reduction treatments on the activity of bark beetles in ponderosa pine stands. Many of the results presented here are preliminary in nature.