This small caterpillar is responsible for a large amount of defoliation of our deciduous shade and ornamental trees. Generally green to blackish in color, these inchworms will feed from April until June. Cankerworm, another notable caterpillar in this area, is another defoliator that looks very similar to wintermoth.
One year of leaf feeding by these pests will not likely kill a tree, but if they attack every year, then the tree becomes stressed and vulnerable to secondary pests. These insects are commonly found on fruit trees, maple, ash, oak, and some shrubs. Foliar treatments are the most effective, but systemic injections are available for trees where access is limited.