Billbugs are weevils that attack turfgrasses as well as a wide variety of other grasses and grasslike plants. The two most important on turf are the bluegrass billbug and the hunting billbug. The bluegrass billbug attacks Kentucky bluegrass, tall fescue, red fescue, and perennial ryegrass. The hunting billbug damages zoysiagrass and bermudagrass. In the southern United States, it also attacks bahiagrass, centipedegrass, and St. Augustinegrass. Damaged turf turns brownish and is easily pulled up in tufts because the root system is being eaten away. Frass that looks similar to sawdust is usually present at the crown. Damage usually appears as roundish, brown areas in the same general area year after year. Adult billbugs are poor fliers, resulting in infestations staying somewhat localized.

Billbugs tend to overwinter as adults, about 1/4 inch long and blackish. They are very hard shelled and have an elongated “snout” that contains tiny chewing mouthparts at the end. When digging in turf, you can sometimes find whitish to brownish adults. These callow adults have recently emerged from pupae and have not “tanned” to their final color. The adults are active on warm winter days and throughout the spring, when they can be found along the edges of sidewalks and in the turf.

Adult billbugs feed on the stolons and crowns of turfgrass. They insert their eggs into stems and leaf sheaths. The resulting larvae tunnel through the leaf sheaths and stems until they are too large to fit inside, at which point they leave the stems and move into the soil to feed on the roots and stolons. The larvae, which are white with brown heads, are plump and legless. Mature larvae are 1/4 to 3/8 inch long. The larvae pupate three to five weeks after hatching, with the adults emerging from pupae.

Due to the longevity of the adults, larvae can be found at any time of the year, although they are most common in June and July. In the last week of April, hunting billbug larvae were found in large numbers in the St. Louis area feeding on zoysiagrass. These larvae were found four to six inches below the surface, probably in response to a recent cold spell. The mild fall and winter may have resulted in a higher level of late-season egg-laying and larval feeding.

Control adult billbugs with foliar sprays of chlorpyrifos (Dursban) or other labeled insecticides at this time of year. Larvae are usually controlled in June and July with imidacloprid (Merit) or halofenozide (Mach 2). Endophyte-containing grasses have been found to be effective against bluegrass billbug.