Several species of webworms (Crambus spp.) may occasionally be found feeding on seedling corn plants. Webworms overwinter as caterpillars in the soil and around grassy plants. They eat a wide variety of grasses. Webworms typically construct a silken tunnel in the soil, leading to the host plant. The short (1/4 to 1/2 inch long), hairy, usually spotted, and active caterpillars are most often found in or near the silken tunnel. Damage ranges from foliage feeding where leaves will show holes and ragged edges, to small seedlings being cut off, resembling cutworm damage.
Webworms can be found in most corn fields at very low levels but seldom pose an economic threat. Populations can be much higher when corn is planted after spring plowing of pasture or especially when sod is herbicide killed and planted with no-tillage methods. If necessary, webworms can be controlled with insecticides. The normal scouting methods employed in seedling corn will detect economic infestations if properly done. Sometimes webworms are one of several seedling insect pests acting in concert to threaten a seedling stand. See scouting guidelines for seedling pests.