Spruce beetle exists across a wide geographic range, extending from Alaska through most of Canada and across much of the western United States. Much of the research on spruce beetle management has occurred within these highly varying forest types and the recommendations gleaned from those studies are often available through a quick online search. However, things are always different in Alaska. While there are certainly management tactics that are effective in many locations throughout spruce beetle’s range, not all tactics that are recommended elsewhere in the U. S. or Canada are effective here.
Pheromones
Commercially available pheromones for tree protection from bark beetles have had limited success in Alaska. Pheromones are chemicals released by one individual to communicate with another individual of the same species. Spruce beetles release a “mass attack” pheromone to signal to other spruce beetles in the area that good host material is nearby. They can also release an anti-aggregation pheromone when there are enough beetles and no more room in the host, almost a “no vacancy” warning. Synthetic formulations of the anti-aggregation pheromone have been developed and studied for use as a repellent against spruce beetles. Results have been mixed on the efficacy of these products in Alaska, and issues with protection tend to be related to the rate of release and zone of protection for individual trees or wide-area protection. Improvements to dispensers are ongoing as are efforts to test their effectiveness in Alaska.
Tarping (solarization)
Likewise, solarization, or covering wood piles with plastic to trap heat, has not been proven successful in Alaska because it does not get hot within the pile for long enough to kill the beetles. This is another area where more research is needed in Alaska to refine the recommendations. Initial studies were completed on the Kenai Peninsula in the 1990’s. As temperature trends change, reviewing this work and testing in other parts of the state could provide additional information about this strategy as a control option.