Impacts of the forest tent caterpillar in forests

Although growth loss can be significant, most deciduous trees can survive two to four years of heavy defoliation by forest tent caterpillars. Heavily defoliated trees often compensate by producing a second crop of foliage. Research reported that aspen normally experienced only a slight growth reduction during the first year of defoliation. However, subsequent years of defoliation caused a 90% reduction in growth, and a15% reduction the year after the defoliation ended. This shows that aspen can recover after defoliation is ended.

However, trees in poor health or under drought stress may decline and die after repeated severe defoliation. Furthermore, defoliation will sometimes cause stress in otherwise healthy trees which may attract secondary pests. For example, oak trees that suffered severe defoliation by forest tent caterpillars are often later killed by two-lined chestnut borers (Exits DNR), or by root and butt rot fungi, called Armillaria (Exits DNR ). When trees die, they provide more space, light, and nutrients for understory species. Forests continue to grow. Outbreaks by the forest tent caterpillar are a natural, periodic occurrence in the forest.