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Japanese beetles in yards and gardens

Quick facts

Japanese beetles are an invasive species.

  • Japanese beetles feed on the leaves, flowers or fruit of more than 300 species of plants.
  • Japanese beetle grubs are pests of turfgrass. They chew grass roots, causing the turf to brown and die. Grub-damaged turf pulls up easily from the soil, like a loose carpet.
  • Japanese beetle infestations in Minnesota are mostly found in the Twin Cities metropolitan area and southeast region of the state.

  • There are both nonchemical and insecticide options for managing Japanese beetle adults and grubs.

The Minnesota Department of Agriculture monitors this invasive species. Please report Japanese beetles you spot at Arrest the Pest.

Japanese beetles (Popillia japonica) were first found in the United States in 1916, after being accidentally introduced into New Jersey. Until that time, this insect was restricted to Japan where it is not a major pest. This pest is considered to be an invasive species. It is now found throughout the eastern U.S., except for Florida, and continues to move westward.

Japanese beetles were first discovered in Minnesota in 1968. At first, only a few beetles were found. By 2001, they occurred in much higher numbers. In one year the Minnesota Department of Agriculture (MDA) trapped more than one million beetles. Since then, Japanese beetle numbers have fluctuated from year to year.

Japanese beetles are most commonly found in the Twin Cities metropolitan area as well as southeast Minnesota. The MDA maintains an updated distribution map of Japanese beetles.

japanese beetle crawling on edge of a leaf

How to identify Japanese beetles

Adult

  • Approximately 1/3 to 1/2 inch long.
  • Metallic green head and thorax (the area behind the head) with copper-brown wing covers.
  • Sides of abdomen have five white patches of hairs, and tip of abdomen has two patches of white hair.

Larva (white grubs)

white c-shaped grub with brown head and visible legs and dark colored large end lying on dirt
  • C-shaped, white to cream-colored grubs with a distinct tan-colored head.
  • Legs are easy to see.
  • From 1/8 inch up to about one inch long.
  • Japanese beetle grubs look like other white grubs and can only be positively distinguished by examining the pattern of spines and hairs on the underside of the tip of the abdomen.
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Japanese beetles are crawling on some of the leaves of a plant with many eaten leaves.

Damage caused by Japanese beetles

Japanese beetles are a serious pest of flowers, trees and shrubs, fruits and vegetables, field crops and turf. Adults feed on more than 300 plant species, whereas the grubs feed mainly on the roots of grasses.

Adult Japanese beetle damage

Adult Japanese beetles feed on the leaves, flowers and fruits of many different plants. Preferred plants include rose, grape, linden, apple, crabapple, cherry, plum and related trees, birch, elm, raspberry, currant, basil, Virginia creeper, hollyhock, marigold, corn silks and soybean.

They skeletonize leaves by feeding on tissue between the major veins giving them a lace-like appearance. Damaged leaves turn brown and may fall off.

Rose with holes in petals and two Japanese beetles crawling on it.

Adult Japanese beetle damage usually affects only the appearance of plants.

  • Healthy, mature trees and shrubs can tolerate a lot of feeding without significant, long-term injury.

  • Young or unhealthy plants may be stunted, injured or even killed from severe, persistent feeding.
  • Healthy flowering plants such as roses can survive Japanese beetle feeding. But the blossoms are often ruined by the insects.
  • Fruits, vegetables and herbs can tolerate limited leaf feeding, but severe damage may affect plant growth and reduce yield.
  • Regular harvesting during July and August can decrease feeding on edible parts of the plant.
Many Japanese beetles crawling on a red raspberry plant in a garden

Japanese beetle grub damage

Grubs chew grass roots and reduce the ability of grass to take up enough water and nutrients to remain healthy. When grub feeding is severe, dead patches of grass develop.

These dead patches can be rolled back like a carpet due to the lack of roots. If grubs are not found, examine still living turf at the edges of damaged areas for their presence.

Healthy turf grass can typically tolerate up to 10 grubs per square foot. Follow recommended lawn care practices to promote a healthy lawn.

Moles, skunks, crows and other insect-feeding animals may dig up grubs, further damaging the turf.

Managing adult Japanese beetles

  • Japanese beetles can be very abundant in some years and less in others.
  • Japanese beetles are not the end of the world. There are many ways to deal with them.
  • In most cases, Japanese beetle damage is cosmetic only and will not kill plants.
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Managing white grubs

Controlling Japanese beetle grubs is unlikely to reduce numbers of adults on landscape plants because beetles emerging from non-treated grass areas can fly considerable distance to preferred adult food plants. Only treat white grubs to protect lawns from damage.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

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Jeff Hahn, Extension entomologist and Julie Weisenhorn, Extension educator

Acknowledgement

Special thanks to Dan Potter, University of Kentucky, for his review and comments of this publication. 

Reviewed in 2018

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