The FTC is a native insect and has evolved in the forest ecosystem for thousands of years. Natural control mechanisms have also evolved which help to keep outbreaks from seriously damaging forested areas. A natural control mechanism that causes population collapse is starvation induced by the caterpillars' feeding. During the early stages of an outbreak, the trees have enough foliage to support the increasing number of caterpillars. After a year or two of complete defoliation, the large number of caterpillars need more foliage than is available.
Late spring frosts that defoliate the trees have much the same effect.
However, frosts hard enough to cause complete defoliation to all the trees species at the same time are not common. Defoliating frosts force the young caterpillars to wait 7-10 days for refoliation. Frost is the only factor that can cause a collapse during the first years of an outbreak. Another significant natural control occurs near the end of the outbreak cycle. A native fly species, Sarcophaga aldrichi, kills many FTC pupae in their cocoons.