Japanese Beetles

Japanese Beetle

Learn organic and natural methods for getting rid of Japanese beetles on lawns and landscaped areas.

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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.

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 cover (Harvest-Guard®) can be used as a physical barrier to prevent adult beetles from damaging plants.
  • Spread beneficial nematodes on lawns or mulch around plants to kill immature stages. These microscopic, worm-like parasites actively hunt, penetrate and destroy grubs in the soil.
  • Milky Spore (Bacillus popilliae) is a naturally occurring host specific bacterium that attacks the destructive white grubs in turf. Apply 10 oz per 2,500 sq ft anytime of year when the ground is NOT frozen.
  • Surround WP (kaolin clay) forms a protective barrier film, which acts as a broad spectrum crop protectant for preventing damage from a large number of insect pests.
  • Azatrol EC contains azadirachtin, the key insecticidal ingredient found in neem oil. This concentrated spray is approved for organic use and offers multiple modes of action, making it virtually impossible for insect resistance to develop. Best of all, it’s non-toxic to honey bees and many other beneficial insects.
  • As a last resort, spot treat adults with botanical pesticides. Apply to all leaf surfaces and deep into the plant canopy where insects hide.

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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