Bark Beetle

Pests

Small beetles that bore through tree bark to lay eggs in the inner bark, creating characteristic gallery patterns and often introducing fungal pathogens.

Bark beetles are small cylindrical insects, typically 2-7mm long, that bore through the outer bark of trees to reach the nutritious phloem layer beneath. There they excavate gallery systems where they lay eggs, and the developing larvae feed as they tunnel outward. Common species include the southern pine beetle, mountain pine beetle, spruce beetle, and various Ips species.

What makes bark beetles particularly devastating is their ability to overwhelm tree defenses through mass attack. Many species use aggregation pheromones to recruit thousands of beetles to a single tree simultaneously, exhausting the tree's ability to produce defensive resin. Additionally, bark beetles often carry symbiotic blue-stain fungi that colonize the sapwood, blocking water transport and hastening tree death.

Bark beetle outbreaks have killed billions of trees across North America in recent decades, driven by drought stress and warming temperatures that accelerate beetle reproduction. Prevention focuses on maintaining tree vigor through proper watering during drought, avoiding root damage, and removing infested trees before beetles emerge. For high-value trees, preventive insecticide bark sprays can deter beetle attack, but they must be applied before infestation occurs.