Billbugs and white grubs are serious pests of turfgrass in parts of Iowa. Both groups of insects feed below ground and damage roots or the growing crown area of the plant. Infestations also may attract predators, such as skunks and raccoons, that dig and damage lawns in search of the insects.
Billbugs are a type of weevil or “snout beetle.” Adult weevils can be seen crossing sidewalks and driveways during late summer or spring. In spring and summer, adults cause minor injuries to grasses as the females cut small holes in the stems of plants and insert their eggs.
The young billbug “grubs” are the primary damaging stage. Billbug grubs are legless, generally white or cream, with a brown head. They may reach 1/3 to 1/2 inch long when full-grown. Young grubs feed within the crown area of the plant and kill it. The stems of infested plants are easily detached at the soil surface. The ends appear sawed-off, often with a sawdust-like material present. Older billbug larvae feed in the lower crown and plant root zone. Small piles of light sawdust-like material are produced during feeding.
Billbug injury is most common on new lawns, particularly those established with sod. Within lawns, most damage occurs near evergreen shrubbery or other protective sites. Billbug injury appears as wilting and occasional death of grass, often in small scattered patches. Extensive areas of a lawn may be killed during severe infestations.
Getting rid of billbugs and grubs in your yard can be accomplished by using the right products at the right time. It is important to note that adult billbugs and billbug larvae are controlled with different products due to their feeding habits and harborage changes in the different parts of their life cycles. Controlling billbug/grub larvae early on is the best way to avoid damage, but billbug larvae can be controlled in either the spring or the summer.