Vermont had severe infestations in the early '50s and late '70s. A building population in the mid-'60s was decimated by late frosts and cool spring weather. Aspen and sugar maple are favored FTC hosts in the Northeast. Apple trees are also commonly infested. Birch, cherry, oak, basswood, and elm are also attacked.
Red maple is avoided.
During outbreaks when trees have been stripped, FTC caterpillars may feed upon brush, fruit trees, and even vegetables. The FTC is a complete leaf defoliator. Heavy attacks on maple sugar orchards may seriously weaken trees and reduce the quality and quantity of sap. Tree death does not usually occur. With each successive molt, the markings of pale bluish lines along the sides of a brownish body and a row of ivory keyhole-shaped spots become more evident on the black back.