Billbugs are a specialized group of weevils or snout beetles.  Several species of billbugs attack turf.  In Oklahoma, the primary pest of bermudagrass is the hunting billbug, Sphenophorus venatus vestitus.  Adult billbugs are gray, black or brown, and measure 3/8 inch long.  They have a beak-like snout and the snout, head, and thorax are about as long as the wing covers.  Billbug grubs are white and legless with a somewhat curved body and measure about 3/8 inch long when fully grown.  Grubs have a brown head capsule and can usually be found in grass stems or thatch.

Life Cycle

Billbugs overwinter primarily as adults, but some larvae also overwinter.  Adult billbugs overwinter in thatch, soil crevices, under bark mulch or leaf litter, or other sheltered places.  Adults become active in spring and wander to find suitable host plants where they mate and begin to lay eggs.  Females lay from 2-5 eggs per day, placed singly in small, chewed cavities of grass stems.  Oviposition is usually complete by mid July, but some eggs are probably laid continuously all summer.

Hosts

The hunting billbug infests zoysiagrass and hybrid bermudagrass but will also feed on bahiagrass, centipedegrass, and St. Augustinegrass.

Damage

Adult billbugs chew holes in grass stems, usually just above the crown to create an egg-laying site.  Larvae begin to tunnel within the stem upon hatching, then burrow into the crown or exit and infest another stem.  Older larvae will feed on the crown and can kill plants.  Injury symptoms are often mistaken for disease (spring dead spot) or winter kill.

Inspection and Control

Billbug activity is often mistaken for disease or winter kill because small patches are killed.  The dead turf will not respond to watering and can be pulled easily from the soil.  Closer inspection will reveal signs of billbug feeding, including hollowed out stems and sawdust.  Larvae may also be found if the stems and crowns are split with a knife and examined.  In spring, billbug adults become active in infested areas and can be seen crawling over paved areas that are near infested turf.  Billbug infestations are most common in highly maintained lawns or sod farms, but they do occur on golf course fairways and other athletic turf.  Bermudagrass seems to be less susceptible than zoysiagrass to severe injury from hunting billbug.  However, improved strains of hybrid bermudagrass are most susceptible to this pest.  Texas researchers report that varieties of Zoysia japonica, which includes “Meyer”, are very susceptible to billbug infestation.  Varieties of Zoysia matrella, which include “Royal” and “Diamond”, are somewhat tolerant.