Caterpillars consume leaves, resulting in naked branches with webbing attached, which contains fecal deposits (frass) or ‘caterpillar poop’. These nests will eventually dry-up as the caterpillars transition into pupae, with adults eventually enclosing (emerging) from the pupae later on in the growing season.
Feeding by fall webworm caterpillars at this time of year is typically not directly harmful to trees—especially larger trees. The most effective method of dealing with fall webworm infestations is to prune out the webs that enclose the caterpillars, place into a plastic bag, and dispose of immediately. Insecticide sprays are not be effective because the caterpillars remain in the webbing while feeding; thus reducing exposure to spray residues. If insecticides need to be applied, use high-volume spray applications that penetrate the protective webbing, or use a rake to disrupt or open-up the webbing so that the insecticide spray contacts the caterpillars.