Billbugs

Billbugs are weevils (genus Sphenophorus) with a long, downward-curved snout; adults are gray to black, about 1/4 to 3/8 inch, and walk slowly across paved areas and turf on warm days. The damaging stage is the legless, white, brown-headed larva found feeding inside grass stems and on crowns and roots. A useful diagnostic is the 'tug test' — damaged stems break off easily and reveal fine, sawdust-like frass (excrement) at the crown.

Yellow-to-brown patches that expand and can coalesce into large dead areas resembling drought stress or summer dormancy; damaged turf pulls up easily and the broken stems contain fine, sawdust-like frass. Adult notch-feeding on leaves is minor compared with larval stem, crown, and root damage.

Billbugs are beetles with complete metamorphosis. Adults overwinter in turf and protected sites, become active and emerge in March-April, and peak in early-to-mid June. Eggs are laid inside grass stems; young larvae feed as stem borers and larger larvae move down to feed on crowns and roots, with damaging larvae peaking in July and August. There is generally one main generation per year in cool-season turf, with additional generations possible in warm regions.

Damage typically appears in mid-to-late summer and is often misdiagnosed as drought or disease. It is most severe in water-stressed turf and is common in Kentucky bluegrass and other cool-season lawns, as well as warm-season turf in the South. Hot, dry midsummer conditions worsen the visible decline because stressed turf cannot mask larval root and crown injury.