Lawns: Billbugs

Problem
The grass turns brown and dies in expanding patches from mid-June to late August. When pulled, the grass lifts easily. Lying in the soil are fat, humpbacked white grubs with brown heads, without legs, and from ¼ to ½ inch long. Black, slow-moving snouted weevils ¼ to ½ inch long occasionally walk on sidewalks and driveways in May and October.

Analysis
(Sphenophorus species)

The larvae of this pest damage lawns by hollowing out the grass stems and chewing off the roots. They can destroy an entire lawn. In May, the adults lay eggs in holes they chew in grass stems. The newly hatched larvae feed inside the stems, hollowing out the stem and crown, leaving fine sandlike excrement. Large larvae feed on roots. Once the larvae move down to the roots and inside the crown, chemical control can't reach them.

Solution
Control billbugs with an insecticide containing diazinon. Young larvae can be controlled if treated while still feeding on the grass blades. If the larvae have already moved down to the roots, then water and fertilize the lawn to stimulate new growth. Repeated treatments are not usually necessary unless the billbugs are migrating from your neighbors' yards. Small damaged areas usually recover if the larvae are killed. Reseed or resod large areas. Next year, treat in early May to kill the adults as they lay eggs. Maintain proper soil moisture and turfgrass fertility programs.