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The Mystery of the Japanese Beetle: Why Is It Such a Problem in North America?
The Japanese beetle (Popillia japonica) is a species of beetle from Japan that is not considered a pest in its native range due to the presence of natural predators. However, when the beetles appeared in North America and parts of Europe, they became a serious pest of many plants, especially threatening about 300 species of plants, such as rose bushes, grapes, hops, bananas, crape myrtles, birch trees, and pine trees. trees and other trees. Not only that, the adults can also damage the leaves of plants and even occasionally eat the fruits of plants, while their underground larvae can damage grass roots.
Adults cause "skeletonization" damage to plants by eating the phloem on leaves, which makes the leaves look hollowed out.
Biology and Characteristics
Adult Japanese beetles are about 15 millimeters (about 0.6 inches) long and 10 millimeters (about 0.4 inches) wide, with dazzling copper-colored outer wings and a green thorax and head. There is a row of white hair-like protrusions on the underside of its wings. The female is slightly larger than the male. The larvae are white, usually in a curved position, and mature larvae are about 1 inch (about 2.5 cm) long.
Distribution and invasion history
The first documented appearance of the Japanese beetle in the United States was in 1916, when it was first discovered in a nursery in New Jersey. It is speculated that the larvae of these beetles entered the United States in a shipment of iris bulbs before the United States began to inspect imported goods. As of 2015, only nine western states in the United States are considered free of Japanese beetles. In Canada, the first Japanese beetle was brought to Nova Scotia by ferry from Maine, USA in 1939.
Japanese beetles have been detected at airports on the West Coast of the United States since the 1940s, and in 2021 more than 20,000 were found in the Grandview area of Washington State.
Life Cycle
Japanese beetle eggs are laid singly or in small groups near the soil surface and hatch into larvae after about two weeks. The larvae feed on fine roots and organic matter, forming a C-shape as they grow and further consume the larger roots. They hibernate and emerge again in the spring. The life span of an adult beetle is between 30 and 45 days, with the majority of time spent in the larval stage.
Prevention and treatment methods
Due to the destructive nature of Japanese beetles, special traps have been developed that use floral scents or pheromones to attract the beetles. However, the study found that many of the attracted beetles did not enter the traps, but instead may have caused greater damage to nearby plants. A milk spirochete vaccine developed by the USDA is effective in controlling the larvae and is also commercially available for lawn control.
Biological control measures such as the Eastokit fruit fly and the solitary Thai monk ant are natural enemies introduced in the United States to control Japanese beetles.
Host Plants
While Japanese beetle larvae feed on the roots of a variety of grasses, adults eat the foliage of a wider range of plants, including common crops such as beans, hemp, strawberries, tomatoes and blueberries.
As the Japanese beetle's range expands in North America, the economic impact and aesthetic damage it causes are undoubtedly causing people to pay attention to this phenomenon. This makes us wonder, how can we effectively respond to the challenges posed by this foreign invader while protecting the ecology?
