JAPANESE BEETLE

 

The Japanese beetle, Popillia japonica Newman, was accidently brought into the United States on nursery stock from Japan about 1916; since then, it has spread throughout most of the eastern United States and become a serious pest of lawns, gardens, shade trees, and orchards (Fleming 1970).

The adult beetle is 10-12 mm long (3/8 to 1/2 inch) with a metallic green body and bronze wing covers. Distinctive tufts of white hair are visible along the sides of the abdomen and behind the wing covers. Larvae are small white grubs with light brown head capsules. They grow to about 15 mm in length (5/8 inch).

Illustrations:

  • Adult stage of the Japanese beetle.
  • Typical feeding damage on blueberry foliage.

    •  

    Life Cycle and Seasonal Distribution


    The larval stages of the Japanese beetle are found in the soil where they feed on the roots of grasses and related plants. Adults emerge in mid-summer, fly to trees or shrubs, and feed voraciously for several weeks on the leaves and fruit. Eventually, the females return to grassy areas to lay eggs. There is only one generation per year (Fleming 1972).

     

    Symptoms and Damage


    Feeding by adult beetles can skeletonize the leaves and cause large, irregular holes in the fruit. Severe damage to the foliage may retard growth in young plants. Infestations are usually easy to detect because the adults tend to congregate on fruit and fly off noisily when disturbed.

     

    Natural Enemies


    Japanese beetle populations are affected by a number of biological control agents. The important parasites include two wasp species that parasitize the larvae (Tiphia vernalis and T. popilliavora), and a Tachinid fly that attacks the adults (Hyperecteina aldrichi). Predation by moles, shrews, skunks, and birds can also account for significant mortality among immature beetles. But the most important natural enemy is probably a bacterial pathogen, Bacillus popillae, the etiological agent of milky spore disease. Beetle larvae ingest the dormant spores of this pathogen as they feed in the soil. The spores are extremely resistant and remain viable in the soil for many years (Rice and Chada 1943).

     

    Scouting, Management, and Control


    Commercial bait traps that combine a floral lure and a sex pheromone attractant (Japonilure) are extremely useful for detecting local emergence of adult Japanese beetles (Ladd and Klein 1982). Large numbers of beetles can be collected in these traps, but there is very little evidence that such mass trapping will significantly reduce defoliation of nearby host plants (Gordon and Potter 1985).

    Good control of local populations can usually be achieved by destroying larval habitats or by treating all permanent sod and grass pastures within one kilometer (5/8 mile) with a commercial suspension of milky spore disease. Insecticide applications should probably be avoided except in extreme cases or on small, non-bearing plants.

    References

  • Fleming, W. E. 1970. The Japanese beetle in the United States. USDA Agriculture Handbook 236 (revised). 30 pp.
  • Fleming, W. E. 1972. Biology of the Japanese beetle. USDA Tech. Bull. 1449. 129 pp.
  • Gordon, F. C., and D. A. Potter. 1985. Efficiency of Japanese beetle (Coleoptera: Scarabaeidae) traps in reducing defoliation of plants in the urban landscape and effect on larval density in turf. J. Econ. Entomol. 78: 774-778.
  • Ladd, T. L., and M. G. Klein. 1982. Trapping Japanese beetles with synthetic female sex pheromone and food-type lures. pp. 57-64. In: A. F. Kydonieus and M. Beroza (eds.). Insect suppression with controlled release pheromone systems. Vol. 2. CRC Press. Boca Raton, Florida.
  • Rice, P. L. and H. L. Chada. 1943. Japanese beetle control by natural enemies. Del. Agr. Exp. Sta. Bull. 244. 22 pp.

    • Last updated: 7 July 1998
    Return to Post-Harvest
    Go on to Autumn.