Japanese Beetle

Order/Family: Homoptera/Aphididae

Description:

  • Adult beetles are ovals, 1/2-inch long with coppery brown wing covers which do not reach the tip of the abdomen. The head, legs and body are metallic green. The body has white patches of hair on each side.
  • Beetle larvae, commonly referred to as white grubs, are worm-like, C-shaped, and at maturity up to 2/3 to 1-inch long. The tip of their abdomen (raster) has two rows of short spines arranged in a V-shaped pattern.

 

Biology and Habits:

  • Japanese beetles are found in most states East of the Mississippi River.
  • Larvae overwinter in the soil. Typically the adults emerge in June.
  • Females lay their eggs in batches (1 – 4 eggs) in the upper three inches of the soil, typically in turf areas near where the adult beetles are feeding.
  • Eggs hatch within two weeks, and the grubs feed on grass roots in the upper two inches of soil. They continue to develop until late fall or first frost when they begin to burrow deeper into the soil to overwinter.
  • Japanese beetles have a one year life cycle.
  • Adult beetles feed at night on nearby trees, cause little damage, and return to the soil during the day.

 

Turf Attacked:

  • Grubs – roots of cool-season and warm-season turfgrasses, turf weeds and other plants.
  • Adults – ornamental plants and trees.

 

Damage:

  • Grubs feed on grass roots cutting them completely off just below the soil line. Severe damage is most evident from late August through early October.
  • The grass dies in irregular brown, spongy patches which can be easily rolled back like a carpet.
  • Collateral turf damage can be caused by animals, e.g., skunks, opossums, birds, and racoons which dig in the ground for grubs.
  • Look for adults on preferred plants from June through early August.
  • Adults feed on the top of plants leaves leaving a skeleton of veins. Leaves eventually darken, die, and drop off. Entire plants may be defoliated.