Managing Douglas Fir Beetle Infestation on Steep Lakeside Slopes

Understanding the Threat

Dead trees with emerged beetles are no longer a threat. Trees with active broods (recently attacked) must be removed to reduce population.

Pheromone Use

Pheromones bait trap trees—concentrate beetles for removal. Anti-aggregants can protect standing trees but require EPA registration.

Recommended Action

• Apply preventive insecticide (e.g., Onyx) to high-value trees.
• Contact Montana DNRC Forestry for on-site assessment: dnrc.mt.gov/forestry/assistance/pests/default.asp.
• Retain dead trees for slope stability if no active beetles and no fall hazard.

Key Takeaway

Distinguish active vs. inactive infestations. Use preventive sprays and professional guidance for complex terrain.