The Japanese Beetle (Popillia japonica) is a beetle about 0.6 inches (1.5 cm) long and 0.4 inches (1 cm) wide (smaller in Canada), with shiny copper-colored elytra and a shiny green top of the thorax and head. Although it is not very destructive in Japan, where it is controlled by natural enemies, in America it is a serious pest to rose bushes and other plants. It is a weak flyer and drops several centimeters when it hits a wall. Japanese Beetle traps therefore consist of a pair of crossed walls with a bag underneath, and are baited with floral scent, pheromone, or both.
As the name suggests, the Japanese beetle is native to Japan. The insect was first found in the United States in 1916 in a nursery near Riverton, New Jersey. It is thought that beetle larvae entered the United States in a shipment of iris bulbs prior to 1912 when inspections of commodities entering the country began.
Life cycle and control
The life cycle of the beetle is typically 1 year in most parts of the United States, but this can be extended in cooler climates. In its native Japan, the beetle’s life cycle is 2 years long as a result of the higher latitudes of the grasslands required for the larval stage.
During the larval stage, the Japanese beetle lives in lawns and other grasslands, where it eats the roots of grass. During this stage it is susceptible to a fatal disease called milky spore disease, caused by a bacterium called milky spore, Bacillus popilliae. The USDA developed this biological control and it is commercially available in powder form for application to lawn areas. Standard applications (low density across a broad area) take from 1 to 5 years to establish maximal protection against larval survival (depending on climate), expanding through the soil through repeated rounds of infection, in-host multiplication, release from killed host, and infection. Typically proper application can lead to a 15-20 year period of protection.
Soil-bound larvae are also susceptible to certain members of the nematode families Steinernematidae and Heterorhabditidae. As with milky spore, commercial preparations of these nematode varieties are available.
The primary natural predator found in Japan is the winsome fly (Istocheta (or Hyperecteina) aldrichi), a parasitic fly. Attempts at establishing this predator in the United States have met with limited success, primarily in New England. Alternative predators have shown some potential at serving as biological controls, such as the Spring tiphia (Tiphia vernalis) and Fall tiphia (Tiphia popilliavora) from China and Korea. Also, certain birds (such as the meadowlark and cardinal) and small mammals are significant predators on the adult form.