Japanese Beetle
Egg - Each white, translucent egg is almost spherical in shape and approximately 2 mm in diameter.
Larva - The white, C-shaped grub has a dark brown head capsule and three pairs of legs. Although it is only 2 mm long when it first hatches, the grub may reach a final length of 32 mm. A V-shaped arrangement of setae on its anal segment distinguishes Japanese beetle grubs from similar species.
Pupa - The 13 mm-long, cream to tan colored pupa resembles the adult in appearance except that the appendages are pressed close to the body. It becomes metallic green just before the adult emerges.
Host Plants - The list of Japanese beetle host plants is seemingly endless. Commonly attacked hosts include: cultivated and wild grapes, raspberry, peach, plum, rose, apple, cherry, corn, soybean, Virginia creeper, hibiscus, marshmallow and Indian mallow, hollyhock, dahlia, zinnia, elm, horsechestnut, linden, lombardy poplar, willow, crepe myrtle, bracken and sensitive fern, elder, evening primrose, sassafras, and smartweed.
Damage - Japanese beetles are voracious foliage and fruit feeders. Feeding in June and July causes little injury to soybeans because the plants can compensate for 35 percent or greater foliage loss. Foliage loss greater than 35 percent may occur in spots 0.4 hectares (1 acre) or less in size. Damaged foliage is characteristically ragged, with only the larger leaf veins intact. Stringy, black excrement is also present.
Japanese beetle injury poses a threat from mid-July until August. After this period, the population naturally declines. The beetles have so many host plants that they rarely confine themselves to soybeans.
Life History - Japanese beetle grubs overwinter as third instars within 13 cm of the soil surface. As the soil warms in the spring, the grubs move closer to the surface and feed on fine rootlets. Shortly thereafter, they remain inactive for a 10-day period prior to pupation. After a pupal stage of 8 to 20 days, adults emerge. Emergence usually begins in mid-May in North Carolina and as late as July in Maine. On warm days the beetles fly and often congregate on host plants to feed and mate. In the afternoon, females burrow into loose, moist soil (usually in sod), and deposit one to four eggs. Over her 1.0 to 1.5 month life span, each female produces 40 to 60 eggs. Grubs emerge 2 weeks after egg deposition, feed on rootlets, and remain active until cold weather arrives. In North Carolina, a single generation is produced annually.
