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Fall Webworm

Our pest management technicians are starting to see fall webworms appearing in a variety of different host trees and ornamental shrubs, including cherries, crabapples, birches and walnuts. Their nests (or “webs”) are usually constructed at the ends of branches, unlike the eastern tent caterpillar (seen in springtime) which builds its’ nests in branch crotches. The nests can be quite large, surrounding up to 3 feet of a branch and usually contain dozens upon dozens of caterpillars. They are made of webbing, frass and gnawed leaves. The caterpillars (the larval stage of the insect) can vary in color but are often green colored with a broad dusky stripe along the back and yellowish stripes along the sides. They do damage to the tree by consuming leaves within the web area and then migrating out and skeletonizing other leaves as they grow larger. They rarely kill trees but can ruin their appearance over the course of time and have been known to defoliate trees, causing stress and loss of carbon reserves. There are a number of non-pesticide controls for these caterpillars, most of which are time-consuming and only somewhat effective. Birds and other predators  will consume them if the nests are pulled down from branches by hand and thrown on ground so the insects become visible. Infested limbs can be pruned off, although this may ruin the look of the tree worse than the insect itself. At Fox Tree we usually use reduced risk pesticide treatments with materials such as spinosad or bacillus thuringensis. If you see webs forming on the ends of your trees’ branches, give us a call today.