Japanese Beetle

Learn how to control Japanese beetles in landscaped areas without toxic chemicals or sprays.

Description

An incredibly destructive pest, the Japanese beetle (Popillia japonica) was first discovered on nursery stock in New Jersey almost a century ago. Originally introduced from Japan, it is now found in most states east of the Mississippi River. Isolated infestations have also been noticed in Wisconsin, Oregon and California. Both the adult and larval stage (white grubs) are damaging and can be a problem in lawns, gardens, nurseries, parks, golf courses, fruit trees, and ornamental trees and shrubs.

Adult beetles (1/2 inch long) are metallic blue-green with coppery wing covers. They eat flowers and skeletonize the leaves of over 300 different plant species. Japanese beetles spend about ten months of the year in the ground in the form of a plump, white grub (3/4 inch long). Grubs feed on the roots of a large number of plants. They are especially injurious to lawns, which will show irregularly shaped patches of wilted, dead or dying grass.

Note: In its native Japan, where there is little turf grass available for grub feeding and a large number of natural enemies, this insect is not a serious plant pest.

Life Cycle

Japanese beetles overwinter in the larval (grub) stage. In early spring the larvae move up near the soil surface and feed on plant roots. By late May pupation begins and adults make their appearance in late June and continue activity until September. Eggs are laid in the soil amid the roots of grasses and hatching takes place in about two weeks. The young larvae feed on the grass roots until cold weather arrives, then burrow deeper into the ground and wait out the winter. One generation per year, the life-cycle requiring two years to complete.

Japanese Beetle Control

In the early morning or late evening, shake beetles from plants onto ground sheets and destroy. Place pheromone traps around the perimeter of your property as adults emerge (May-July). Floating row covers can be used as a physical barrier to keep beetles from damaging plants. Spread beneficial nematodes on lawns or mulch around plants to kill grubs in the soil. Milky Spore (Bacillus popilliae), a naturally occurring host specific bacterium, will also attack the destructive white grubs in lawns. Spot treat with botanical insecticides to kill adults feeding on foliage.

Tip: Studies have shown that Lawn Aerator Sandals (a.k.a. Spikes of Death) are equal to or more effective than some insecticides for managing Japanese beetle grubs. Researchers reported killing 56% of the grubs by walking over infested plots of lawn 3-5 times.

Note: The USDA maintains quarantines to restrict the movement of this destructive pest, but they are expected only to delay the spread rather than prevent it.

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