Billbugs are perhaps the most common insect affecting home lawns in Idaho. The adults, which are about 1/4 inch long, can be seen in the spring, walking along sidewalks especially on the southern sides of buildings.
The adults are a black weevil, have a long snout and will play dead when disturbed. The adults do very little damage, but in the larval stage billbugs eat grass stems and roots. Adults become active when soil temperatures reach 55º F, usually early to mid-May. The larvae are small (1/8 – 1/4 inch long), white, legless grubs with a brown head.
Lawns damaged by billbugs look like they are drought stressed because the grass blades are basically severed from the roots. Grass blades can be easily pulled out by hand with a light tug. A healthy, vigorously growing lawn will recover from moderate billbug damage and symptoms may go unnoticed. However, under-fertilized lawns or lawns that are otherwise stressed will be more susceptible to billbug damage.
Control. If you have areas with known billbug problems, control measures should be targeted against the adults in the spring when they are active and seen crawling along sidewalks or other exposed areas. Waiting until damage is visible may be too late since the damage has already been done. If targeting larvae, good coverage and movement of the insecticide past the thatch layer are very important. Since adults are on the surface of the turf, they are more easily contacted with insecticides.