Annual bluegrass weevil

A small (about 1/8 inch) weevil with a curved snout; freshly emerged adults are reddish-brown but darken to black with a gray, scale-covered body. Adults are found on the surface of short turf in spring (a soap flush or vacuum sampling helps detect them), while the damaging legless, cream-colored, brown-headed larvae are found inside and at the base of grass stems. Damage appears first along the margins of golf course tees, collars, approaches, and fairways where annual bluegrass abuts taller grass.

Yellowing, then browning patches that begin along edges of fairways, tees, collars, and approaches and can coalesce; injury is easily mistaken for drought or wilt. Crown-feeding by mature larvae kills annual bluegrass plants, leaving thinned, dead areas that do not recover with irrigation.

The annual bluegrass weevil is a beetle with complete metamorphosis — egg, five larval instars, pupa, and adult. Adults overwinter in leaf litter and taller grass at the edges of wooded areas and migrate on foot into short turf in spring, with peak adult movement near 120-170 growing degree days (base 50F, from March 1). Eggs are laid between leaf sheaths; early instars feed as stem borers and later instars feed externally at the crown. Two to three overlapping generations occur per season in the Northeast.

Damage is closely tied to annual bluegrass (Poa annua) on intensively managed, low-mowed golf turf in the Northeast and mid-Atlantic. The first and most predictable damage cycle appears in mid-to-late May from the spring generation's larvae; later generations can cause additional injury through summer. Damage often starts at the interface between short turf and taller grass where overwintered adults congregate.