Coleoptera: Scarabaeidae


Adults of Japanese beetle are oval in outline from above, almost 10 mm long and 6 mm wide. The head, thorax, and abdomen are metallic green with metallic copper-brown wing coverings. The five patches of white hairs on each side of the abdominal segment distinguish this species from all other similar-looking beetles. The larvae of the Japanese beetle, commonly known as white grubs, are C-shaped, creamy white, and grayish-to-dark to the posterior end. The head is yellowish-brown with strong dark-colored mandibles. Each thoracic segment bears a pair of segmented legs.

Life Cycle

Japanese beetle has one generation per year. The female deposits up to 60 eggs in soil that hatch within seven to 14 days and grubs begin feeding on grass roots. Grubs cease feeding in mid-fall and overwinter below the soil surface about ten months of the year. In early spring, the grubs continue to feed on roots, and in late spring, they change into pupae. In two weeks, the pupae become adults and emerge from the ground to feed on foliage.

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More than 300 species of fruits, garden, and field crops are known to be hosts to Japanese beetle. Adults feed on foliage, flowers, and fruits. Leaves are typically skeletonized or left with only a tough network of veins. Grubs primarily feed on the roots of plants and turf grasses, which can be extremely damaging to young trees and kill them over time. Symptoms are not always immediately visible, and damage may continue unnoticed until a clump of trees declines and dies suddenly. Young trees are susceptible, but older trees are also at risk.

Biological Control