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
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.