Japanese Beetle (Popillia japonica)
by Daniel Frank, WVU Extension Service Entomology Specialist
The Japanese beetle, Popillia japonica, is native to Japan, but has become common throughout much of the eastern United States since its accidental introduction in 1916. The adult beetles feed on the foliage, flowers, and/or fruit of more than 300 different plant species and are considered a major pest of many popular horticultural and agricultural plants. Adult Japanese beetles can cause significant damage to host plants because of their tendency to feed in large numbers.
Adult Japanese beetles are approximately 3/8 inch in length, oval in shape, and have clubbed antennae. They are metallic green in color with coppery-brown wing covers (elytra) and a row of five white hair tufts on each side the abdomen. The larvae are typical white grubs that can be distinguished from other species by the presence of a small V-shaped series of hairs on the underside of the last abdominal segment (raster). Newly hatched larvae are about 1/16 inch long, while the mature larvae are about 1 inch long.
Japanese beetles can damage plants during both the adult and larval stages, but the type of feeding injuries produced by each life stage is very different. Adult Japanese beetles are mainly leaf feeders that consume the tissue between leaf veins. Because the veins of the leaf are left intact, the damage is often referred to as skeletonization. In addition to leaves, beetles will feed on blossoms, as well as ripe or damaged fruit when available. The larvae are a type of white grub that feeds below the soil surface on the roots of grasses and other plants.