Japanese Beetle
Egg - The white or cream colored egg is spherical and about 1.5 mm in diameter when first laid. By the time it hatches, the egg has doubled its original size.
Larva - The grayish-white, slightly curled grub has a dark brown head and measures about 16 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 - Adult Japanese beetles infest over 275 different plants, including corn. Shade and fruit trees, ornamental shrubs, small fruits, garden crops, weeds, and field crops are often damaged also. The grubs are serious pest of lawns, other grasses, and nursery stock.
Damage - Gregarious in nature, Japanese beetle adults are often found feeding in masses on a few plants, leaving others nearby uninfested. On most hosts, leaves are skeletonized and the mature fruit is damaged. However, injury to corn may occur when the beetles feed very heavily on the silks and ear tips thereby reducing pollination and predisposing the ear to other insects and fungi. However, heavy feeding does not necessarily influence pollination and adult injury of this magnitude is rare. In localized spots, larval injury to developing root systems can severely reduce corn stands.
Life History - The grubs overwinter in cells within 13 cm of the soil surface. In the spring, they move upward, almost to ground level, where the complete feeding and pupate. The three larval instars complete development in about 140 days. Adults emerge as early as mid-May in eastern North Carolina and as late as July in New England. Throughout the summer, they attack the fruit and foliage of many plants, including the silks of corn. In North Carolina, peak emergence occurs during July. 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 2 weeks after deposition. The newly emerged larvae feed until cold weather forces them into hibernation. Only one generation occurs each year.