Forest tent caterpillar: impacts

Roles in the forest

feeding on aspen leavesFTCs are native insects and are therefore an important part of our forest ecosystems. While temporary outbreaks may lead to severe defoliation and are a nuisance, these insects' importance in Minnesota forests should not be ignored. Changes in forest dynamics and regeneration patterns have been linked to large outbreaks, and it is likely the forests we see in our state today are the result of periodic FTC outbreaks that have occurred over millennia. Weak, diseased, or stressed trees may be killed by FTC, making way for other tree species better adapted to the site. FTCs also are an important spring food source for squirrels, rodents, bears, and many bird species.


Defoliation from FTCs usually causes little damage to aspen tree health and vigor. Most hardwoods develop a second set of leaves by mid-July. Oaks and birches that are also suffering drought stress or root damage or are overmature become vulnerable to additional "secondary" insects, which can kill them in one to three years. Repeated defoliation of aspen mixed-wood forests by forest tent caterpillars influences forest dynamics, how forests grow.