The white grub is the progeny of the Japanese beetle, a major pest throughout the United States. The white grub, when present in small numbers as it is in most yards, presents little trouble. When a grub population becomes too large, however, your lawn will exhibit droughtlike conditions, including wilting, browning and dying off.
Identifying grubs in the lawn is important for the control process. According to Ohio State University, adult beetles have a metallic green sheen. The adult Japanese beetle is oval and around 3/8 inch long by 1/4 inch wide. The grubs are C-shaped when disturbed from the ground, white, and grow from 1/16 inch to 1 1/4 inches long at different stages of maturity.
Adult Japanese beetles emerge from the ground at the end of June or July to seek out food, and the females lay new grubs at 2 to 4 inches deep. Females lay 1 to 5 eggs before mating again. In her entire life, the beetle will lay 40 to 60 eggs. The eggs hatch in 8 to 14 days. The fist instar grubs shed their skin in 17 to 25 days, then again after 18 to 45 days. The grubs feed on grass roots, causing the most damage in the late summer and early fall. As the weather cools, the grubs dig down in the soil to keep away from the cold. The grubs reemerge in the spring to feed on the grass roots again before forming a pupa.
Hand Picking and Trapping
As Japanese beetles arrive on your property, hand picking can be a somewhat effective method of control. Destroying adults as they arrive reduces the number of grubs laid. Adults are active during the middle of the day and less active during the early morning and the evening. Traps are also available to catch adults.
According to the University of Rhode Island, insecticide is most effective insecticide when applied in the fall. As grubs mature, their skin becomes too strong for insecticides to penetrate effectively. Treatments are best applied between August 1 and September 15. Grub pesticides are available at most garden centers.
Nematodes and Milky Disease
The bacterial milky disease Bacillus popilliae is an effective control of grubs. Spores of the bacteria persist for 2 to 3 years, making it an effective long-term control. The bacteria attack the grubs and kill them. Nematodes, microscopic roundworms, are also grub deterrents. They are commercially available at good gardening centers and online.