Japanese beetle

Popillia japonica

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Japanese beetle pupa moulting 2017

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Istocheta aldrichi egg on Japanese beetle

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Japanese beetle (Popillia japonica) is a species of scarab beetle that is native to Japan. It is well known for its destructive larval and adult stages, which can cause significant damage to a wide range of host plants, including both agricultural and ornamental species. The Japanese beetle was first found in the United States in 1916, near Riverton, New Jersey. Since its introduction, it has become a major pest in many areas of the eastern United States, parts of Canada, and beyond, due to its broad host range and lack of natural predators in these new environments.

Description

The adult Japanese beetle is easily recognizable by its metallic green body and copper-brown wing covers. Adults are about 10-15 mm in length. The larvae, known as grubs, are creamy white in color with a C-shaped body and can be found in the soil, where they feed on the roots of grasses and other plants.

Life Cycle

The life cycle of the Japanese beetle consists of four stages: egg, larva (grub), pupa, and adult. Females lay eggs in the soil during the summer months. After hatching, the larvae feed on plant roots until the weather cools, when they move deeper into the soil to overwinter. In spring, they return to the surface to feed again before pupating. The adults emerge from the soil in late spring to early summer and begin the cycle anew.

Diet and Damage

Japanese beetles are known for their wide range of host plants; they feed on the leaves, flowers, and fruits of over 300 species of plants. This includes, but is not limited to, roses, grapes, beans, and apples. The adults eat the leaf material between the veins, leaving a skeletonized appearance, while the grubs damage lawns and other turf areas by feeding on the roots of grasses.

Control and Management

Managing Japanese beetle populations is challenging due to their wide host range and the mobility of the adults. Control methods include physical removal of the beetles by hand, use of traps, application of chemical insecticides, and biological control. Biological control methods involve the use of natural predators, such as certain species of wasps and flies that parasitize the eggs or larvae of the beetles. Additionally, the use of milky spore disease (a bacterium that specifically targets Japanese beetle grubs) has been effective in reducing grub populations over time.

Impact

The Japanese beetle is considered a significant agricultural and ornamental pest. It causes extensive damage to crops, lawns, and gardens, leading to economic losses for farmers and homeowners. The beetle's feeding habits can weaken plants, making them more susceptible to disease and other pests.

Prevention

Prevention strategies focus on minimizing the spread of the beetles to new areas. This includes inspecting plants and soil before transport and implementing quarantine measures in areas where the beetle is not yet established. Public awareness and education on the impact of the Japanese beetle and how to manage its spread are also crucial components of prevention efforts.