Adult Bluegrass Billbug

Billbugs are weevils that have the snout, head and thorax about as long as the wing covers. Though there are about a half dozen species that may be found in turf grasses, only a few cause damage in any given region. The adults are only 1/4- to 3/8-inch long and dark gray to black. They may be covered with a tan or brown coating of soil. The larvae are white with a brown head and look like legless white grubs.

The bluegrass billbug is most common in the northern states from New England to Washington state. It is found less commonly in southern states.

Kentucky bluegrass seems the preferred host but occasionally this pest has infested perennial ryegrass, red fescue and tall fescue. It also attacks small grain crops such as corn, rye and wheat.

Billbug damage usually appears in late-June through August, when summer drought stress is common. Light infestations in lawns often produce small dead spots that look like the turf disease, dollar spot. Sometimes the damage looks like irregular mottling or browning in the turf. Heavy infestations can result in complete destruction of the turf, usually by August. The major problem with billbug damage is that it looks like a variety of other problems. Most turf managers confuse billbug damage with drought, disease, chinch bugs, greenbugs or white grubs. Billbug damaged turf turns a whitish-straw color rather than the yellow caused by greenbugs. Soil under damaged turf is solid, not spongy as in white grub attacks.

To confirm billbug attacks, grasp the affected turf and pull upward. If the stalks break easily at ground level and the stems are hollowed out or are full of packed sawdust-like material, billbugs are the culprit.

Billbugs are some of the most difficult turf grass insects to control because the adults’ armor-like bodies do not readily absorb insecticides. They also do not ingest much insecticide when they penetrate a grass stem while feeding. The larvae are also difficult to control because they are boring inside grass stems for much of their lives.

Neighborhoods with mixed-grass lawns or lawns established using resistant varieties are often less severely attacked. Wise turf managers take time to observe all the turf in an area and watch for the beginnings of billbug attack in a neighborhood. Although bluegrass billbugs rarely fly, they may rapidly spread through continuous lawns of a neighborhood.

*This information was extracted from the Ohio State University Extension Fact Sheet HYG-2502-91.