Description: Billbugs are gray, brown, or nearly black beetles with a long snout. Adults of the several species range from 1â„5 to 3â„4 inch long. Billbugs hide at the base of plants during the day, are frequently covered with soil, and play dead when disturbed. The eggs, which they lay in plant stems, are white to gray and kidney-shaped. The adults frequently gouge out holes in unfolded leaves in which to lay their eggs, and these spots appear as a transverse row of punctures in the expanded leaves. The larvae, off-white, legless, brown to yellow headed, humpbacked grubs, feed in the center of the lower section of plant stems or in the roots. They pupate either in the stems or in the soil among the roots.
Damage Symptoms: Adults chew through young plants forming rows of oval holes across emerging leaves. Larvae feeding inside the base of the stem and roots cause serious injury; feeding by several larvae on a single plant may prevent ear development. Injured plants are usually tillered (multiple shoots) and stunted with twisted leaves.
Scouting: VE through V4. Scout in low-lying, wet areas of the field that have weedy grasses or yellow nutsedge. Check plants with injured leaves and look at the base of plants for beetles hiding in the soil or in crop residue.
Management: Rescue treatments maybe warranted when the damage is widespread and the billbugs can be found.Â
Sources:
University of Illinois
Iowa State University Extension, Corn Field Guide: A reference for identifying diseases, insect pests and disorders of corn. 2009: 50.
