The Japanese beetle, Popillia japonica, is one of the most common pests encountered by Pennsylvania fruit growers, nursery operators, and gardeners. It is often the most important pest of tree-ripened peaches and can cause severe damage to other important crops.
The Japanese beetle is beautifully colored--the head, thorax, and abdomen are bright metallic green, and the legs are dark green. Coppery brown wing covers extend near the tip of the abdomen, where two prominent white tufts of hair occur. Five similar tufts occur along the side of each wing cover.
The egg is pearly white, elliptical, and 1/16 inch in diameter. The soft-bodied grub is "C" shaped, whitish with a brown head, and 1 inch long at maturity.
The Japanese beetle overwinters in the soil as a grub and completes its growth in early spring. Adults emerge in greatest numbers during July and are active for a month. The gregarious beetles are most active on warm, sunny days on favorite hosts. Adults enter the ground in the early evening.
During their life cycle, females lay 40 to 60 eggs that hatch in 2 weeks. Grubs feed on organic matter and fine grass roots until late fall. They reach maturity in early spring and, after spending 3 to 4 weeks in the pupal stage, emerge as adults. Only one generation is hatched each year.
Beetles chew leaf tissue between veins and leave a lacelike skeleton. Severely injured leaves soon turn brown and often drop. The fruit of early ripening peach trees might be gouged in irregular, shallow patches or completely devoured.
Fruit and foliage can be protected by using a broad-spectrum insecticide beginning when beetles first cause injury and as necessary when beetle feeding causes unacceptable damage. Since sprayed trees can be reinvaded, they should be inspected weekly when adults are present.