Egg -- The translucent white to cream-colored egg is elliptical and about 1.5 mm in diameter when first laid. By the time it is ready to hatch, the egg is more spherical in shape and has doubled in original size.
Larva -- The grayish-white, slightly curled grub has a yellowish-brown head and measures about 26 mm long when mature. It can be distinguished from other white grubs by two rows of spines which form a "V" on the underside of its last abdominal segment.
Pupa -- The cream-colored pupa, approximately 13 mm long and 6 mm wide, gradually turns light brown and finally develops a metallic green cast.
Host Plants -- The grubs are serious pests of lawns, other grasses, and nursery stock. Tender grasses are preferred to tougher varieties. The adult beetles infest over 275 different plants, including many shade and fruit trees, ornamental shrubs, small fruits, garden crops, and weeds.
Damage -- Japanese beetle grubs may be abundant in well-kept lawns, pastures, and golf courses. They burrow through the soil, severing and consuming roots. Large areas of dead brown grass often appear in infested lawns when large numbers of grubs (10 per 929 sq cm or 10 per sq ft) are present or duing dry spells. Such dead areas are noticeable by September or early October. Unlike the grubs, Japanese adults eat foliage, leaving only a lacy network of leaf veins.
Life History -- The grubs overwinter in cells within 13 cm of the soil surface. In spring, they move upward, almost to ground level, where they complete feeding and pupate. About 140 days elapse from egg hatch to larval maturity.
Adults emerge as early as mid-May in eastern North Carolina and as late as July in New England. However, even in the beetles' southernmost range, peak emergence occurs in July. Throughout summer, the beetles attack the fruit and foliage of many plants. Soon after emerging, females deposit 40 to 60 eggs in small batches 5 to 8 cm deep in the ground. Under extremely dry conditions, many eggs and larvae perish. However, during warm, wet summers populations thrive and eggs hatch about two weeks after deposition. The newly emerged larvae feed until cold weather forces them into hibernation. One generation occurs each year.
Soil insecticides may be used in late summer or early fall to control grubs feeding near the soil surface. The residual life of the soil-applied chemicals is relatively short, necessitating repeated applications each season. For specific insecticides and rates, consult the state agricultural extension service recommendations.