Bark Beetle
Scolytinae subfamily
high risk
insect
Overview
Small beetles that bore beneath tree bark to breed. Native species are natural parts of forest ecology but invasive species and population explosions during drought kill healthy trees.
Adults tiny, 1-9mm, cylindrical, dark brown to black. Galleries (egg tunnels) visible under bark. Shot-hole size exit holes in bark.
Prevention Strategies
- •Maintain tree health through watering and nutrition - healthy trees resist attack
- •Prompt removal of recently killed trees to reduce local populations
- •Avoid wounding trees (beetles attracted to sap)
Control Methods
- •Lindane or permethrin bark sprays for high-value trees
- •MCH pheromone repellent
- •Systemic insecticides for some species
- •Remove and destroy infested trees promptly
- •No treatment possible once tree is dead
Interesting Facts
- •Mountain pine beetle has killed over 70 million acres of forest in western North America
- •Climate change is primary driver of current bark beetle outbreaks
- •Some bark beetles farm fungi inside their galleries for food
- •A healthy tree can drown attacking beetles in resin - mass attacks overcome this defense