Japanese Beetles


As its name suggests, the Japanese beetle (Popillia japonica) is native to Japan and the first documented sighting in the United States was in a nursery in New Jersey in 1916 (www.aphis.usda.gov/plant_health/plant_pest_info/jb/). It is thought that the larvae were transported here in a shipment of iris bulbs (www.entomology.wisc.edu/mbcn/fea508.html).

In its native country the Japanese beetle is kept in check by cool summer temperatures and natural predators (specifically, a parasitic fly) and is not considered to be a serious plant pest. In the United States, where it has no natural enemies, it is a significant pest with the grubs feeding on grass roots and causing damage to lawns and golf courses. The adults feed on the foliage, fruit and flowers of more than 300 different plant species, often skeletonizing the leaves of, or defoliating completely, their favored host plants.

The favorable conditions in the Eastern United States have led to the beetle becoming well-established in most of the States east of the Mississippi, and in a few States west of the Mississippi, such as Arkansas, Iowa, Kansas, Minnesota, Missouri, and Oklahoma. Strict regulations and monitoring have kept the beetle from becoming established in the Western States.


Life Cycle

 Japanese Beetle Life Cycle

Illustration by PPQ employee
Joel Floyd, used with permission from USDA

Adult beetles typically emerge from the ground in lthe last week of June through July. The first adults to emerge release a congregation pherome that attracts other beetles to gather on the favored host plants (http://ohioline.osu.edu/hyg-fact/2000/2504.html). The adult females also produce sex pheromones in order to attract mates. After mating, females burrow into the soil and lay 1-5 eggs at 5-10 cms below the surface. Once the eggs have been laid the female returns to the surface and feeds and mates again before returning to the soil to lay more eggs. Females repeat this cycle until they have produced 40-60 eggs. The feeding, mating and egg laying cycle typically lasts until mid-August. Individual beetles live 30-45 days.


The eggs absorb moisture from the soil and swell. The eggs and newly hatched larvae will dry out if moisture levels are low, so irrigated lawns are particularly attractive for e