On the Move: Hunting Billbugs
The number of occurrences of hunting billbug (Sphenophorus venatus vestitus) damage from both adults and larvae has increased over the last 20 years in the United States. This increase might be due to a number of factors including better diagnostic skills. Hunting billbug damage is often misdiagnosed as drought, grub damage, turf dormancy or another insect pest. Hunting billbugs attack warm season residential lawns and commercial sites. Susceptible turfgrass species include zoysiagrass, where the hunting billbug might be referred to as Zoysia billbug, bermudagrass, centipedegrass and St. Augustinegrass.
Adult females begin to lay eggs starting in spring and continue through the fall. The adults normally appear gray to black in color normally six to 11 mm in length. The weevil is often coated with soil, which combined with its normal white powdery appearance, gives the adult a “dirty” look. Some confusion may occur with the adult color. Upon emergence, young adults will have a reddish-white color. These adults will turn black in a relatively short time. Normally, we do not consider adults to be the damaging stage. That is reserved for the larva. However, a strong correlation has been found at North Carolina State University between symptoms that are similar to “dry patches” and large number of hunting billbug adults in the fall prior to injury symptoms.
Figure 1. Adult hunting billbugs
Once the eggs hatch, the larvae produced are considered to be the damaging stage. The larvae feed during the summer months. What makes hunting billbug damage difficult to diagnose is that damage is not normally detected during the summer because the warm season turfgrasses may literally grow out of the damage. Symptoms are most noticeable during the fall through early spring when turf growth has slowed. Through the transition zone and into northern parts of the southern states like Alabama and Arkansas normally one generation of hunting billbug occurs during the season. As you move further south into Texas and Florida two to three generations can occur.
Figure 2. Larva of the hunting billbug
Diagnosis is often difficult. Symptoms appear as small circular spots to large blighting of turf. The symptoms appear in color quite similar to what fertilizer burn would look like. If billbug damage is suspected, a good diagnostic key is to tug or pull on discolored plants. If the plants are easily pulled up, it is a good chance that billbugs are the problem. Additionally, the sheaths or stems are hollowed out.
Hunting billbugs are most effectively controlled chemically. However proper grass selection can make control easier. For example, Zoysia matrella is more resistant to billbugs than Zoysia japonica. Although not related to warm season turfgrasses, endophyte containing cool season turfgrass are billbug resistant.
Chemically controlling hunting billbug is often dependent on the biology of the insect. Adults can be controlled with a number of various pyrethroid insecticides including lambda-cyhalothrin (Scimitar). Adult control is usually considered in situations where hunting billbug injury is a perennial problem. For larvae control longer lasting insecticides like thaimethoxam (Meridian) and chlorantraniliprole (Acelepryn) would be recommended. If both adult and larvae control are required immediately, Acelepryn would be recommended.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: