Adult Japanese beetles are 3/8-inch long metallic green beetles with copper-brown wing covers. Five small white tufts projecting from under the wing covers on each side, and a sixth pair at the tip of the abdomen, distinguish them from similar beetles.
Adults emerge from the ground and begin feeding on plants in June. Individual beetles live about 30 to 45 days. Activity is concentrated over a four-to-six-week period, beginning in July, after which the beetles gradually die.
Japanese beetles can feed on about 300 species of plants ranging from roses to poison ivy. Odor seems to be a very important factor in the selection of a suitable food plant. They usually feed in groups, starting at the top of a plant and working downward, and prefer plants exposed to direct sunlight. A single beetle does not eat much; it is group feeding by many beetles that causes the severe darnage. Adults feed on the upper surface of foliage, chewing out tissue between the veins. This gives the leaf a characteristic skeletonized appearance. They tend to do little feeding on thick, tough leaves.
The spread of the Japanese beetle infestation is primarily the result of flight by the adults. Although they can fly as far as 5 miles, flights of 1 to 2 miles are more likely. Usually, they make only short flights as they move about to feed. Local infestations spread as beetles move to favored food and suitable sites for egg laying.
Beetles are fond of certain weeds and non-economic plants such as bracken, elder, multiflora rose, Indian mallow, sassafras, poison ivy, smartweed, wild fox grape and wild summer grape. Elimination of these plants whenever practical destroys these continuous sources of infestation.
