See bulletins of the U.S. Dept. of Agriculture.
Scarab beetle (Popillia japonica) that is a major pest of plants. Introduced accidentally from Japan into the U.S. in 1916, Japanese beetles are known to feed on more than 200 species of plant. Their larvae feed underground on roots; adults feed on flowers, fruit, and foliage. They range from Maine to South Carolina, and infestations have occurred in other parts of North America. The adult, about 0.4 in. (10 mm) long, is bright metallic green with coppery-brown wing covers. Control efforts include the use of poisonous sprays and a disease-inducing bacterium and introduction of the beetle's natural enemies (certain parasitic wasp and fly species).
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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. However, studies done at the University of Kentucky suggest that traps attract more beetles than they actually trap, thus causing more damage than may have occurred were the trap not used.
Japanese beetles have a curious, identifying defense: they lift their hind legs up in the air, even when simply approached. These hind legs are spiny, and the behavior is probably intended to ward off predators.
These insects damage plants by eating the surface material, leaving the veins in place, producing a curious, but alarming to the experienced gardener, "transparent leaf" effect on its victims.
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.
The life cycle of the beetle is typically one year in most parts of the United States, but this can be extended in cooler climates; for instance, in its native Japan, the beetle's life cycle is two years long as a result of the higher latitudes of the grasslands required for the larval stage. During the larval stage the white grubs can be identified by their V shaped raster pattern.
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 Tiphiid wasps Tiphia vernalis and 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.
Research performed by many US extension service branches has shown that pheromone traps may attract more beetles than they catch, and so they have fallen out of favor. Natural repellents include catnip, chives, garlic, and tansy, as well as the remains of dead beetles. Additionally, when present in small numbers, the beetles may be manually controlled using a soap-water spray mixture.
Japanese Beetles feed on a large range of hosts, including leaves of plants of the following common crops:
and these genera: