Occasionally I encounter a weakened lawn or athletic field that appears to have symptoms of drought stress, or disease attack even though adequate water and preventative fungicides have be applied. Upon closer examination billbugs, small turf feeding weevils, are found. Adult billbugs are hard bodied, usually grayish or black, 1/4 inch in length, and have long beak-like snouts with chewing mouthparts at the tip. Billbug larvae are small, 3/8 inch or less, cream colored legless grubs with yellowish brown heads.
The adults will deposit tiny eggs into the stems and crowns of the turf plants where the young larvae then feed until they become too large then move into the thatch where they continue to feed on stolons, rhizomes and roots. While zoysia and hybrid Bermudagrass lawns are most often preferred they will also feed on Bahiagrass, centipede, and St. Augustine lawns. The adults and larvae have been feeding most of the summer but the symptoms get more pronounced near the end of summer as turf growth slows, along with hot, dry conditions. As cooler weather approaches in the fall the adults will begin to seek sheltered sites in which to overwinter.
Use a shovel to lift a small one foot square section of the turf with about an inch of soil from the ground for close inspection for evidence of the grubs as you crumble the soil from the turf roots. While the best management for control is to apply a preventative insecticide in the spring prior to egg hatch conventional soil insecticides can be applied in the spring or fall to kill adults and larvae feeding on crowns, stolons, and roots. For more detailed information on billbugs and other lawn pests control recommendations refer to extension publication #2331 “Control Insect Pests in and around the Home Lawn”.
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. firstname.lastname@example.org