Insect Problems - Japanese Beetles

SYMPTOMS

Leaves have netted appearance from leaf tissue being eaten between the veins. Flower buds may also be eaten. The tree will have a ragged, tattered appearance.

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Damage has a netted appearance
where the leaf has been eaten away
between the veins.

DESCRIPTION OF PEST

Adult beetles are less than ½ inch long. They have a metallic green head and thorax with copper-colored wings. There will be 12 tufts of white hairs around the sides of the abdomen. Larvae are white C-shaped grubs ½ to 3/4 inches long, with a light brown head and legs. The larvae can be identified from other beetle grubs by the V-shaped pattern of hairs on the raster (bottom rear of abdomen).

LIFE CYCLE

Eggs are laid in the soil one to four inches deep in mid to late summer and hatch after about two weeks. The young grubs feed primarily on the roots of lawn grasses until the onset of cold temperatures where they go deeper into the soil for the winter. As the soil warms again in the spring, the grubs move upward to resume feeding on roots until pupating near the soil surface in early summer. Adults emerge in early to mid summer and feed on the leaves of many species of trees and shrubs.

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The adult has a metallic green head and
thorax with copper-colored wings.


MANAGEMENT


CHEMICAL
Insecticides can be applied as needed to valued plants to protect from feeding injury of adults. Lawn insecticides can be applied in late spring and late summer or early fall to control the grubs. An application of a lawn insecticide about three weeks after the adults have disappeared will do a good job of controlling the young grubs which are very close to the soil surface. Contact you local Extension Service for specific pesticide recommendations for your area.

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Japanese beetle grub (larvae) found
in the soil.

BIOLOGICAL
Traps are available which attract and capture adult beetles. These need to be placed far away from plants that you are trying to protect. They also need to be emptied frequently to remain effective and to reduce the stench associated with the dead beetles.

Milky spore, Bacillus popilliae, is a bacterium that, when present in the soil, can help in the control of the grubs. Because such a large area needs to be treated for a significant impact on the beetle population, it is usually not an effective treatment for individual homeowners.

 

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Japanese beetle grubs can be identified
by the V-shaped arrangement of hairs
on the raster.
 

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