- Adult billbugs are about 1/4 to 1/2-inch long from the tip of the snout to the end of the wing covers.
- The snout, head, and prothorax ( body segment between wings and head) are as long as the wing covers.
- Billbugs are gray to black; however, their wing covers vary:
- Bluegrass – lined wing covers with evenly spaced pits.
- Denver – rows of paired “deer hoof print-like” depressions
- Hunting – Y-shaped mark on the pronotum with ( ) shaped lines on either side.
- The pale, legless larvae are C-shaped, and at maturity are 1/4 to 3/8-inch long.
Biology and Habits:
- Bluegrass billbugs occur throughout the US and southern Canada.
- Denver billbugs occur in the Rocky Mountain States.
- Hunting billbugs occur in southern US and Hawaii.
- The adults overwinter under leaf litter and in tufts of grass and become active in April – May. In warmer climates billbugs are active all year. Denver billbugs overwinter as mature larvae.
- Females lay eggs inside the leaf sheath.
- Th larvae hatch within a few days and tunnel and feed in the grass stem. As the larvae mature (35-55 days) they become too big to feed in the stem, so emerge from the stem and begin feeding on the grass crowns, destroying several in the process. This is when the most severe damage occurs. Peak larval populations and feeding occurs July – August.
- Generations may overlap, and all life stages can be found at the same time.
- There is one generation per year. In the southern rage of hunting billbugs there may be several generations per year.
- During the day adults hide in the grass and come out to feed at night.
- Bluegrass billbug – Kentucky bluegrass, perennial ryegrass
- Denver billbug – Kentucky bluegrass, perennial ryegrass
- Hunting billbug – zoysia, bermuda, bahia, centipede and St. Augustine grasses
- Adults chew holes in stems and leaves.
- Larvae feeding in the stem cause the center of the leaf to turn yellow and die.
- The damage starts as small yellow dying patches which may become much larger as the season progresses.