Caterpillars are slightly more than 1 inch long and covered with long, pale, gray hairs. The body color ranges from yellow to brown with dusky, mottled areas along the sides and two rows of black dots along the back. Most characteristic are the large, silk webs that encircle the ends of branches.
Over 100 species of hardwoods are recorded as hosts. Preferred species include black walnut, ash, hickories and oaks.
Moths emerge in the spring and lay eggs. The newly hatched larvae construct webs which they enlarge as needed. Larvae feed gregariously within the web for 4 to 8 weeks. After feeding, the larvae migrate and pupate in the soil. There are two generations per year.
Although not considered a serious forest pest, their unsightly webs can affect aesthetic value of landscape and roadside trees. Biotic factors usually keep populations in check so that chemical control is only rarely necessary.
UMD Fall Webworm-trees
50 Harry S. Truman Parkway, Annapolis, MD 21401