Insect Outbreaks in the Northwest

Northwest forests are home to many species of native insects that live in and feed on trees. These insects thin old, stressed, or sick trees and diversify forest structure. Under certain conditions, forest insects can also cause significant tree mortality when their populations expand in an outbreak. This fact sheet summarizes the conditions that effect insect outbreaks, highlights two prominent species, and presents some general considerations for managing insect outbreaks. 

This sheet was produced as a partnership between the Western Wildland Environmental Threat Assessment Center and the USDA Northwest Climate Hub.