How to Get Rid of Japanese Beetles

Quick answer: Japanese beetles are controlled by hand-picking them into soapy water in the morning, covering plants with netting, and using traps carefully. Treating lawns for their grubs, for example with beneficial nematodes, helps reduce next year’s beetles.

The Japanese beetle (Popillia japonica) is a shiny green and copper beetle that eats the leaves and flowers of hundreds of kinds of plants. It is a serious garden pest in much of the eastern and midwestern United States, but there are many safe ways to keep it under control.

Japanese beetle Quick Facts

Common name	Japanese beetle
Scientific name	Popillia japonica
Kingdom	Animalia
Phylum	Arthropoda
Class	Insecta
Order	Coleoptera
Family	Scarabaeidae
Genus	Popillia
Type	Insect (scarab beetle)
Diet	Leaves, flowers and fruit of hundreds of plants; grubs eat grass roots
Habitat	Gardens, lawns, farms and parks
Native range	Japan; introduced to North America and parts of Europe
Size	About 1 cm long
Lifespan	About 1 year; adults live 4-6 weeks
Colours	Metallic green head and thorax, copper-brown wing covers

Getting to know the Japanese beetle

Japanese beetles are native to Japan. They were first found in the United States in 1916, in a plant nursery in New Jersey, probably after arriving as grubs in the soil of imported plants. With few natural enemies to stop them, they spread across much of the eastern half of the country and beyond.

Adults are about 1 cm (less than half an inch) long. They have a metallic green head and thorax and shiny copper-brown wing covers. A good way to identify them is the row of five little tufts of white hair along each side of the body, plus two more at the tail end.

How to spot the damage

Adult Japanese beetles eat the soft tissue between the veins of leaves, leaving behind a lacy skeleton. This is called skeletonizing. They also chew flowers and fruit. The beetles feed in groups, and the smell of damaged plants attracts even more beetles, so the damage can build up quickly.

Their larvae, called grubs, live underground and eat grass roots. A lawn with lots of grubs may get brown, dead patches that peel up like a loose carpet.

Life cycle

Japanese beetles usually have one generation a year. Adults come out of the ground in early summer, often from late May to July depending on the area. Each adult lives about four to six weeks.

Females lay their eggs in the soil, often in lawns. The eggs hatch into small white C-shaped grubs that eat roots through late summer and fall. In winter, the grubs move deeper into the soil. In spring they move back up, feed again, then pupate and come out as adults. The grub stage lasts about ten months, most of the year.

Tips to get rid of Japanese beetles

Getting rid of Japanese beetles completely is very hard once there are lots of them. The best approach is to spot them early and use several methods together.

Know their favorite plants

Japanese beetles have favorite foods. Knowing them helps you check the right plants first, choose less tempting plants, or remove weedy favorites. Some plants they love include:

• Roses
• Grapevines
• Smartweed
• Elder
• Bracken
• Mallow
• Morning glory

Pick them off by hand

Hand-picking works well in small gardens. The best time is early in the morning, when the beetles are cool and slow. Hold a bucket of soapy water under a leaf and tap the beetles into it. When disturbed, they tend to drop straight down, so they fall right in. Doing this every day or two early in the season makes a big difference, because fewer beetles means fewer beetles being attracted.

Keep plants healthy and covered

Healthy plants handle beetle damage better. Water them well, and pick up overripe fruit and spent flowers, which can attract beetles. For small, valuable plants, you can cover them with fine netting while the adults are active. Remove netting from plants that need bees to pollinate their flowers.

Try companion plants

Some gardeners grow plants that Japanese beetles seem to dislike near their favorites. Popular choices include garlic, catnip, chives and tansy. The results are mixed, so use companion plants as an extra helper, not the only plan.

Be careful with beetle traps

Japanese beetle traps use scents to lure the beetles. They catch a lot of beetles, but studies show they often attract more beetles into the area than they catch, which can make damage worse. If you use them, put them far away from the plants you want to protect.

Plant-based sprays

Products made from neem oil can make leaves less tasty to Japanese beetles and reduce feeding. An adult should always choose and use any spray, follow the label carefully, and avoid spraying flowers when bees are visiting.

Dealing with the grubs

Grubs in the lawn are the next generation of beetles, so controlling them can help, especially if your neighbors do the same. Good natural options include:

• Beneficial nematodes: Microscopic worms that hunt grubs in the soil. They work best in moist soil in late summer, when grubs are young.
• Milky spore: A natural soil bacterium that infects Japanese beetle grubs. It works slowly, over several years, and is most useful in warm areas.
• A healthy lawn: Thick, well-watered grass with deep roots can handle more grubs without showing damage.

To check how many grubs you have, mix about 2 tablespoons of dish soap in a gallon of water and pour it over a small square of lawn. Grubs and other soil insects will wriggle up to the surface within a few minutes, and birds may help clean them up. If you find only a few grubs in a square foot, the lawn usually does not need treatment.

Japanese beetle FAQs