How to get rid of Japanese beetles

Japanese beetles (Popillia japonica) eat the leaves, flowers, and fruit of more than 300 kinds of plants. They show up in early summer and feed for about 6 to 8 weeks. In a bad year, they can turn rose leaves into lace in a few days.

How to identify Japanese beetles

• About 1/2 inch (1.3 cm) long
• Shiny, metallic green head
• Copper-brown wing covers
• Five small tufts of white hair along each side, plus two at the tail end

The white tufts are the easiest way to tell them apart from look-alike beetles.

The damage looks like lace. Japanese beetles eat the soft leaf tissue between the veins and leave a skeleton behind. They feed in groups, often at the top of the plant in full sun.

Plants Japanese beetles love

Their favorites include roses, grapes, raspberries, linden trees, Japanese maples, birch, hollyhocks, basil, and beans. Fruit trees like plums and cherries get hit too.

The Japanese beetle life cycle

Japanese beetles have one generation a year.

1. Adults come out of the soil in early summer.
2. Females lay eggs in lawns and other grassy areas.
3. The eggs hatch into white, C-shaped grubs that eat grass roots in late summer and fall.
4. Grubs move deeper in the soil for winter.
5. In spring, they move up, feed again, and turn into adults.

This life cycle gives you two chances to fight them. You can go after the beetles on your plants, and the grubs in your lawn.

1. Hand-pick them into soapy water

Hand-picking is the simplest control, and it works well in small gardens. Go out in the early morning, when beetles are cool and slow. Hold a bucket of soapy water under the leaves and tap the branch. The beetles drop straight down to escape, right into the bucket.

Pick every day. Leaves damaged by feeding give off scents that draw in more beetles. Removing beetles early keeps the crowd smaller.

2. Cover your best plants

Fine mesh netting or row cover keeps beetles off. Use it on roses, berries, and young trees during peak beetle season. On fruit plants, wait until the flowers are pollinated before you cover them.

3. Skip the bag traps

Japanese beetle traps use a floral scent and a sex pheromone to lure beetles in. They do catch a lot of beetles. But research at the University of Kentucky found that traps draw in more beetles than they catch. Plants near the traps can end up with more damage, not less.

If you use traps at all, put them far away from the plants you want to protect.

4. Spray as a last resort

Sprays are a backup for heavy years. Read the label, and spray in the evening when bees are not out.

• Neem oil products can discourage beetles from feeding. Spray when the beetles first show up.
• Kaolin clay sprays coat leaves in a thin white film that beetles avoid. They are used on fruit like grapes and apples.
• Pyrethrin sprays kill beetles on contact. They also harm bees, so never spray open flowers.

5. Treat the grubs in your lawn

Fewer grubs this fall means fewer beetles next summer.

• Beneficial nematodes. Heterorhabditis bacteriophora nematodes hunt grubs in the soil. Apply them in late summer, when grubs are young and close to the surface. Water the lawn before and after, and apply in the evening, since sunlight kills nematodes.
• Milky spore. This bacterium (Paenibacillus popilliae) infects Japanese beetle grubs. It takes a few years to build up in the soil. It needs warm soil to work, so results in cold climates are mixed.

Treating your own lawn will not stop beetles flying in from the neighbors. Over time, though, fewer grubs mean fewer beetles.

Japanese beetles in British Columbia

Japanese beetles are common in parts of eastern Canada and the United States. In British Columbia, they are a newer pest, and governments are working to wipe them out.

The CFIA (Canadian Food Inspection Agency) first found Japanese beetles in BC in 2017, in the False Creek area of Vancouver. The CFIA now has regulated areas in Vancouver, Burnaby, Coquitlam, Port Coquitlam, and Kamloops.

Do you live in a regulated area? Then you need a CFIA movement certificate to move plants with soil attached out of it. This rule applies all year.

Think you have seen a Japanese beetle in BC? Report it to the CFIA. Do not move plants with soil out of a regulated area without permission. You can check the current maps on the CFIA Japanese beetle page.

Protect the plants they love

These posts help you grow the plants Japanese beetles target most:

• How to grow roses
• How to grow raspberries
• Growing Concord grapes
• How to grow basil

For other common pests, see my guide to garden pests.