The Japanese beetle, a most destructive garden pest, devours just about everything in its path — including well-tended trees and shrubs. The damage this invasive insect causes is disheartening, but you can arm yourself with knowledge and keep Japanese beetles under control in your yard:
The Japanese beetle is a native of Japan, where it has natural enemies that help control beetle damage and keep beetle populations manageable. The U.S. Department of Agriculture reports that the first U.S. sighting of this foreign menace was in a New Jersey nursery in 1916.1
Because very few natural enemies of the beetle exist in the United States, this pest has wreaked havoc on plants since it arrived. It took only four years for the Japanese beetle to cause severe damage in 22 states after making its way to America. Monitoring and rigid regulations have tried to slow its spread, but its range is expanding steadily.1
At slightly less than 1/2 inch long, the Japanese beetle is hardly imposing. Under different circumstances, this destructive pest might be considered attractive. The oval-shaped insect is metallic green with bronze-colored wing covers and dark legs. A telltale characteristic that distinguishes the Japanese beetle is the series of small, white tufts of hair located under the wing covers along each side of its body and on its hind end.
In the spring or early summer, adult female beetles lay eggs in soil. Those eggs hatch and become unattractive larvae known as white grubs. The white grubs have brown heads and feed on plant roots, often causing severe lawn damage. If disturbed, the grubs curl into a C shape. The larvae stay in the soil until the following spring, when they pupate and become adults.
Because of this hungry invader's distinctive feeding pattern, Japanese beetle damage to trees and shrubs is easy to spot. The pests dine on the soft tissue between leaf veins, leaving foliage skeletonized and lace-like. Flower petals become ragged after beetles feed on them. Trees hit hard by Japanese beetle feeding appear as though scorched by fire.2
Japanese beetles are most active on warm, sunny days and like to feed in direct sun in groups. The adult beetles can fly, which allows them to move easily and quickly to congregate throughout your landscape. They begin eating at the top of plants and work their way down.3
The Japanese beetle's voracious appetite makes it especially destructive. The adult beetle feeds on more than 300 species of plants — including roses, shrubs, vines, ornamental and fruit trees, and vegetable crops — devouring leaves, flowers, tree and shrub buds, and fruit.2
If you have Japanese beetle problems, avoid planting large numbers of plants known to attract these pests. These are just a few of the ornamental plants, shrubs and trees preferred by these pesky pests: