Forest tent caterpillar: Impacts

Roles in the forest

Forest tent caterpillars 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, their 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.  Wildlife can also benefit from FTC; they are an important spring food source for squirrels, rodents, bears and many bird species.

Impacts    

Defoliation from FTC 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, root damage or are over-mature become vulnerable to additional "secondary" insects which can kill them in one to three years. FTC play critical roles in structuring aspen mixed-wood forests. A recent study by the University of Minnesota showed that the repeated defoliation of aspen mixed-wood forests by forest tent caterpillars is linked to forest dynamics, how forests grow.