Protecting your trees from Mountain Pine Beetle – what works, what doesn’t.

With Mountain pine beetle populations on the rise, many homeowners would like to protect their trees from being killed. There are many products out there that claim to protect trees from mountain pine beetle, and some of them have more science and field-testing backing them than others.

Pheromones are a hot topic right now. These are essentially powerful scents that insects use to communicate. One is an antiaggregation pheromone called verbenone, which acts to tell other beetles that “this tree is full.” Research on this has shown that it works pretty well while beetle populations are low. However, the pheromones don’t kill the beetle – they merely divert them to a neighboring property where the populations will continue to build. When populations increase (epidemic levels), the synthetic material is not able to ‘mask’ the communication system of the beetle, and it loses efficacy. Additionally, research has shown mixed results on the use of these pheromones in a natural forest setting. Verbenone is commercially available, and registered in Colorado; landowners should have their property assessed by a professional forester before deciding to use verbenone. It is not a “silver bullet”, but it may temporarily help in an area where the beetle populations have not built up. It should be used in conjunction with an aggressive plan of searching out and treating infested trees.

Tree injections have also received a certain amount of media attention. With this system, a systemic insecticide called emamectin benzoate (EB) is injected into the trunks of trees. Mountain pine beetle has recently been added to the pesticide label. Applications work best if applied prior to insect infestation. The health of the tree, as well as environmental conditions will determine the rate of uptake. Soil moisture must be adequate and the tree must not be drought stressed. Retreatment every year is required.

Certain formulations of carbaryl (Sevin and others) permethrin (Astro, Dragnet and others), and bifenthrin (Onyx) are registered for use to prevent attacks on individual trees. These sprays are applied to living green trees in early summer to kill or deter attacking beetles. This preventive spray is generally quite effective through one MPB flight (one year).