Forest Pest Insects in North America: a Photographic Guide

Spring cankerworm

Paleacrita vernata (Peck) (Lepidoptera: Geometridae)

Orientation to pest

Spring cankerworm, Paleacrita vernata (Peck), is a native North American moth that defoliates many hardwood species and in some locations goes into periodic outbreaks. Damage is caused by young "inchworm" larvae skeletonizing new leaves and older larvae consuming all but the larger veins or midrib. This species may be confused with the very similar fall cankerworm, Alsophila pometaria (Harris). Adults emerge from pupal cells in the soil in early spring when the ground is thawed. Females crawl up tree trunks to lay eggs, which are deposited in loose clusters of 100 or more in bark crevices or under bark scales. Eggs hatch in early spring and larvae feed on leaves through the end of spring. Mature larvae drop to the soil on silk threads in summer. Larvae remain dormant within their soil-covered pupal cells throughout the rest of the summer and fall, pupating in late fall or early spring. There is one generation per year.

Hosts commonly attacked

In North America, larvae of this moth feed on many hardwood species, including elm (Ulmus), green ash (Fraxinus pennsylvanica Marsh.), maple (Acer), bur oak (Quercus macrocarpa Michx.), linden/basswood (Tilia), silver birch (Betula pendula Roth), and apple (Malus domestica Borkh.).


This geometrid is found in southeastern Canada, as well as throughout the northeastern and north central United States, and west to parts of Texas, Colorado and California.

Images of spring cankerworm

Wingless female adult of spring cankerworm Mark Ascerno, University of Minnesota, University of Minnesota • Extension 288x153
Male adult of spring cankerworm Nolie Schneider, 768x512
Larvae of spring cankerworm James B. Hanson, USDA Forest Service, 768x512 / 1536x1024
Larvae of spring cankerworm USDA Forest Service - Northeastern Area Archive, USDA Forest Service, 768x512 / 1536x1024
Tree trunk with band trap to catch female spring cankerworms as they crawl up trees William A. Carothers, USDA Forest Service, 768x512 / 1536x1024
Figure 1. Adults of spring cankerworm, Paleacrita vernata;
top: wingless female, bottom: male
Figure 2. Larvae of spring cankerworm Figure 3. Tree trunk with band trap to catch female spring cankerworms as they crawl up trees

Important biological control agents related to this pest species

Several species of parasitoids are known from spring cankerworm, including three braconids, Rogas geometrae Ashmead, Apanteles paleacritae Riley, and Meteorus hyphantriae Riley. It is also attacked by the ichneumonids Phobcampe geometrae (Ashmead) and Hyposoter fuscitarsis (Vierieck). Bacillus thuringiensis Berliner is bacterium that has been formulated as a biopesticide that can be used to control larvae of this species.

Web links for information on spring cankerworm