Japanese beetle

The Japanese beetle (Popillia japonica commonly referred to as the jitterbug) is a beetle about 1.5 cm (0.6 inches) long and 1 cm (0.4 inches) wide (smaller in Canada), with shiny copper-colored elytra and a shiny green top of the thorax and head. It is not very destructive in Japan, where it is controlled by natural enemies, but in America it is a serious pest to rose bushes, grapes, canna, crape myrtles, 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. 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.

History

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

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.

Control

During the larval stage, the Japanese beetle lives in lawns and other grasslands, where it eats the roots of grass. During that stage, it is susceptible to a fatal disease called milky spore disease, caused by a bacterium called milky spore, Paenibacillus (formerly 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 one to five 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 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.

On field crops such as squash, floating row covers can be used to exclude the beetles, however this may necessitate hand pollination of flowers. Kaolin sprays can also be used as barriers.

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.

Host Plants

Japanese Beetles feed on a large range of hosts, including leaves of plants of the following common crops:

Strawberries, tomatoes, peppers, grapes, roses, plums, pears, peaches, raspberries, blackberries, corn, peas, blueberries

and these genera:

• Abelmoschus
• Acer
• Aesculus
• Alcea
• Asparagus
• Aster
• Betula (Birch trees)
• Buddleja
• Calluna
• Caladium
• Canna
• Chaenomeles
• Cirsium
• Cosmos
• Dahlia
• Daucus
• Dendranthema
• Digitalis
• Dolichos
• Echinacea
• Hemerocallis
• Heuchera
• Hibiscus
• Humulus
• Hydrangea
• Ilex
• Impatiens
• Iris
• Lagerstroemia
• Liatris
• Ligustrum
• Malus

• Malva
• Myrica
• Ocimum (Basil)
• Oenothera
• Parthenocissus
• Phaseolus
• Phlox
• Physocarpus
• Pistacia
• Platanus
• Polygonum
• Populus
• Prunus
• Quercus
• Rheum
• Rhododendron
• Rosa
• Rubus (Raspberry, blackberry, etc.)
• Salix
• Sambucus
• Sassafras
• Solanum
• Syringa
• Tilia (Linden, lime, or basswood trees)
• Toxicodendron
• Ulmus
• Vaccinium
• Viburnum
• Vitis
• Weigelia
• Wisteria
• Zea
• Zinnia

References

External links

• APHIS web page on beetle management
• Japanese beetle on the UF / IFAS Featured Creatures Web site