Japanese Beetle

Denise Attaway  |  4/28/2011 7:41:27 PM

Japanese beetles are best detected on blueberry bushes during calm, hot, cloudless afternoons. Photo by Jerry A. Payne, USDA/ARS.

C-shaped grubs are found in soil under grassy areas. Photo courtesy of the University of Maryland Cooperative Extension Service Plant Diagnostic Website.

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Japanese beetle adults are about 1/2 in. (13 mm) long with a metallic green head and thorax, and reddish-brown wing covers.


  • Usually complete about one generation per year, although a full life cycle may take two years in the coldest regions of Japanese beetle distribution.
  • Mating occurs as soon as females emerge from the ground. Then, they seek grassy areas with moist soil to lay eggs.
  • Eggs are  .04 inches to .08 inches (1 mm to 2 mm) in diameter, spherical and white, and are laid about 2 inches to 4 inches (5 cm  to 10 cm) deep in the soil in batches throughout the female beetleā€™s month-long life.
  • C-shaped, cream-colored grubs with brown heads and three pairs of legs develop in the soil, becoming 1.18 inches (3 cm) long when fully grown.
  • Eggs are laid in the ground; the small, white larvae, called grubs, feed on the roots of grasses.


  • Larvae sometimes kill roots of grasses they feed on.
  • Adults destroy leaves, flowers and fruits they feed on.


  • Beetles are best detected on blueberry bushes during calm, hot, cloudless afternoons.
  • Traps for monitoring Japanese beetle are highly attractive but can increase the number of beetles flying into an area.

  • In small plantings, beetles can be removed from bushes.
  • Control of attractive weed hosts and removal of grassy areas in and around fields can reduce field suitability for Japanese beetles.
  • Biological control agents suppress populations in areas where the beetle is established.
  • Check with your local Cooperative Extension Service office for control measures recommended for your area.


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