At Boreal Tree Care we have decided not to spray pesticides to attempt and suppress Spruce Bark Beetles due to the environmental risks and concerns with broadcast spraying. What we do offer is trunk injection of insecticides. The product we use has the trade name Boxer and the active ingredient Emamectin benzoate, which stays active for 2 years in the tissues of the tree. The injection of chemicals is relatively new to the state of Alaska, and there is not a wide breadth of information on their use. I (Bill) have personally used them on hundreds of trees in Anchorage over the last 5 years and had success suppressing the beetles.

Trunk injection works by injecting the chemical directly into the conductive tissues of the tree, the tree then takes the chemical moving it through the rest of the tree, protecting it from the inside out. One advantage of this method is the chemical will eventually be translocated through the entire tree. Foliar sprays often will not reach the top of the larger spruce trees, leaving the upper portion of the canopy vulnerable to beetle attack above the spray line.

One of the main unknowns with this chemical and application method is how long it take trees in Alaska to translocate the chemicals though out the entire canopy of the tree. With the chemical staying active in the tree for 2 years, I recommend that the trees be treated again every 18 months giving 6 months of overlap for the newly applied chemical to be moved though-out the canopy. One downside to this suppression method is that the tree is not immediately protected once it is treated. With the time it takes the tree to move the chemical, the tree may not be totally protected until the following season. By injecting every 18 months there will be some active chemical in the tree due to the overlap, and the tree will have protection as long as the applications are repeated.

There have not been any scientific studies performed on spruce trees in Alaska as of July 2022 on this topic. A study was done by the US Forest Service in the mountains of Utah on a different species of spruce that showed the injection of emamectin benzoate to be effective in reducing tree fatalities from spruce bark beetles. That study is linked below. The information above is my opinion as an ISA Certified Arborist and based on my experience and observations in 5 seasons using Boxer (active ingredient Emamectin benzoate) to suppress Spruce Bark Beetles in Anchorage. Please contact us to discuss this service further, and to see how it would apply to the trees on your property.

US Forest Service Study on Injection of Emamectin Benzoate in Spruce for Beetle Protection