Japanese Beetle (Popilla japonica)

Japanese Beetle (Popilla japonica) Top

The Japanese Beetle (Popilla japonica) is in the Scarab Beetles Family (Scarabaeidae). This pest was introduced to North America in the early twentieth century from Japan, whence its name. Unlike Japan, North America has few predators of this beetle. Therefore, the Japanese beetle has thrived in North America where it does great damage to over 200 species of plants. The photographs on this page show Japanese Beetles eating the foliage of a Beaked Hazelnut shrub, a member of the Birch Family, along the shore of French Hill Pond. They will only eat the cells of the leaves between the veins, a process called "skeletonizing." Birches and maples are favorite foods of these creatures.

These beetles are easy to identify. They grow to ⅜ to ½ inches (8 to 12 millimeters) long. The body is metallic green. Their forewings (elytra) are metallic brown or reddish orange. There are five patches of white hair on either side of the rear part of the body. The underside is covered with gray hair. The male Japanese Beetle has pointed spurs at the end of the legs, The female has rounded spurs.

Japanese Beetle (Popilla japonica) Front

The female beetle deposits one to four yellow to white eggs in soil during spring. These eggs hatch larvae that overwinter in Maine. The larvae consume the roots of grasses. Adults emerge from these larvae the next summer.

The most effective control of these bugs is to kill the larvae with the bacterium Paenibacillus (Milky Spore). The adults are more difficult to control. Traps may be effective but must be deployed exactly as the manufacturer directs or the traps may attract Japanese Beetles to nearby plants. Small infestations are best controlled manually by spraying the plants with soapy water, shaking or picking the beetles off the plant and crushing them. Covering plants with a fine mesh will often keep the beetles away.


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