Fall Cankerworm (Lepidoptera: Geometridae), a Native Defoliator of Broadleaved Trees and Shrubs in North America

The fall cankerworm, Alsophila pometaria (Harris), is a species endemic to North America that feeds on broadleaf trees and shrubs. Fall cankerworm is a generalist folivore and larvae feed on a wide range of deciduous trees and smaller woody plants. Common hosts include oak, maple, cherry, ash, apple, beech, and birch. This pest is prone to repeated outbreaks over large areas, can cause extensive defoliation throughout hardwood forest stands, and can be a public nuisance in developed or highly populated areas. Fall cankerworm defoliation can lead to reduced tree health and impact ecosystem function, carbon sequestration, wildlife habitat, and temperature regulation, especially in urban areas. Elevated populations often occur in areas where host trees are stressed or a high density of a preferred host species is present. Fall cankerworm management is often necessary due to their impacts on the local tree canopy and nuisance to the public. Tree banding and the use of the biological insecticide Bacillus thuringiensis (Bt) are the common management tactics used to reduce fall cankerworm populations. Here we review fall cankerworm distribution, life stages, host plants, damage, scouting and sampling procedures, management options, and discuss commonly associated and co-occurring defoliator species.