Egg - The tiny eggs are oblong and pale.
Larva - The larvae vary from pinkish-white to yellowish to light brown. When fully grown they are 16 to 19 mm long and have thick bodies, coarse hairs, and paired dorsal spots and lateral spots on each segment.
Pupa - The reddish-brown pupae are about 13 mm long.
Host Plants - Webworms primarily infest the roots of many grasses causing problems in lawns, golf courses, and pastures. They are usually a threat to field crops such as corn and tobacco only when these crops follow sod. Some species overwinter near the roots of weeds such as stickweed, plantain, and fleabane.
Damage - Webworms attack the roots of seedling corn plants. The larvae feed on the stalk at or below the soil surface. As the leaves emerge, they are ragged, distorted, and almost perpendicular to the stem. When webworm damage is heavy, the whole plant may be curled or twisted and the growing point killed. Careful examination around the base of an infested plant will reveal scarred or damaged tissue on one side of the stem plus at least one hole extending into the center of the plant. Fine silken strands intermingled with bits of plant material or soil pellet cocoons are usually present.
Life History - Webworms overwinter within silk-lined tubes in the soil. Early in the spring, they emerge and feed at night on roots of grasses, weeds, and cultivated plants. In southern states, larvae have usually completed feeding by June 1, whereas in Ohio and Indiana feeding may continue until July 1. When mature, the larvae pupate within a silk-lined cocoon made up of soil particles and leaf blades interwoven with silk. Moths emerge 10 days to 2 weeks later, push their way to the soil surface, and mate soon afterwards. For the few days that they live, female moths fly at dusk and drop eggs over grassy areas. Eggs hatch in approximately 7 days. Depending on geographic location and the particular webworm species, these pests complete one to three generations each year.
For further control information, consult the current North Carolina Agricultural Chemicals Manual.