Japanese Beetle Control: Protect Your Plants Without Making It Worse

It is late June, and your roses, grapes or linden tree are covered in shiny green and copper beetles. Within days the leaves look like lace. Those are Japanese beetles, and they show up in groups that can strip a favorite plant fast. This guide helps you confirm what you have, protect the plants you care about most, and avoid the most common mistake: hanging a beetle trap.

How to identify Japanese beetles

Adult Japanese beetles are hard to mistake once you know what to look for:

• About 1/3 to 1/2 inch long.
• Metallic green head and thorax.
• Copper-brown wing covers.
• Five small tufts of white hair along each side of the abdomen, plus two more at the tip. This is the clearest field mark.

The larvae are white grubs that live in lawns and eat grass roots. They look almost the same as other lawn grubs. If you are dealing with brown patches in the lawn, read the grub control guide.

Signs of Japanese beetle damage

• Skeletonized leaves. Beetles eat the soft tissue between the veins and leave a lacy network behind. Badly hit trees can look scorched.
• Damaged flowers and fruit. Rose blooms, grapes, raspberries and fruit trees are favorites.
• Groups of beetles feeding together on the same plant.

A single beetle eats very little. The damage comes from many beetles feeding on the same plant at once. Feeding beetles release scents that draw in more beetles, which is why one plant can get hammered while the one next to it looks fine.

Healthy, established trees and shrubs usually tolerate the damage, and most of it is cosmetic. Young or stressed plants can be stunted or killed.

Why Japanese beetles show up

Adults come out of the soil from late June, with peak activity lasting about four to six weeks. Each beetle lives about a month to six weeks. Females lay eggs in the soil, often in lawns, and the grubs feed on grass roots through late summer and fall. They spend the winter deeper in the soil and move back up in spring.

Adults fly well and are drawn to favored plants from a distance. That means the beetles on your roses may have grown up in a neighbor’s lawn or a park down the street.

How to get rid of Japanese beetles, step by step

Start with the least-toxic steps, following the integrated pest management order. In most home gardens, hand-picking and better plant choices are enough.

1. Check plants daily once the first beetles appear. Catching the early arrivals matters most, since their feeding attracts more beetles.
2. Hand-pick into soapy water. Fill a bucket or wide jar with water and a squirt of dish soap. In the early morning or evening, when beetles are cool and slow, hold the container under a branch and tap or shake it. Beetles drop straight down and drown. Pick off the rest by hand.
3. Cover prized plants. Drape cheesecloth or fine netting over roses or small shrubs during peak feeding. On plants that need pollinators, hand-pick until bloom ends, then cover.
4. Leave beetles with small white eggs on them alone. Those eggs belong to a parasitic fly that helps control the beetles.
5. Use an insecticide only for plants you cannot otherwise protect. See below.

Do not hang Japanese beetle traps. The lures are very good at pulling beetles in from a wide area, but traps catch only part of what they attract. University of Kentucky research found traps drew in far more beetles than they caught, so plants near the trap often took more damage. Iowa State and Minnesota extension specialists also advise against them. Iowa State notes one exception: very lightly infested sites, or places far from other beetle populations.

Plants Japanese beetles prefer and avoid

Adults feed on more than 300 kinds of plants, but they have strong favorites. If you are planting new trees or shrubs in an area with heavy beetle pressure, lean toward the “seldom damaged” list.

Crabapples vary a lot by variety. Some are hit hard and others resist damage, so check before you buy.

Insecticides for Japanese beetles

If hand-picking cannot keep up on a plant you care about, sprays can protect the foliage for a while. They do not reduce the number of beetles flying in, so expect to repeat.

• Short-lived, lower-risk options: neem products and pyrethrins deter or kill beetles for only a few days. They need direct contact and repeat applications.
• Longer-lasting contact sprays: pyrethroids (such as bifenthrin, cyfluthrin, deltamethrin, lambda-cyhalothrin and permethrin) protect leaves for about two to three weeks, and carbaryl for about one to two weeks. These are toxic to bees, so do not spray open flowers or plants where bees are foraging.
• Chlorantraniliprole lasts two to four weeks on foliage and is low risk to bees. Minnesota notes it is sold mainly to professional applicators.
• Insecticides that move through the plant, like imidacloprid and dinotefuran, go on the soil once a year and are very toxic to pollinators. Minnesota advises keeping them at least 4 to 5 feet away from plants that attract pollinators.

The University of Kentucky rates insecticidal soap, garlic, hot pepper and orange peel extracts, and companion planting as generally ineffective against Japanese beetles. Read and follow the label on any product, and check that it lists the plant you want to treat. Our guide to using pesticides safely covers labels and storage.

Does treating lawn grubs help?

Only for the lawn. Because adults fly in from other properties, killing grubs in your own yard rarely cuts down on beetles feeding on your roses. Treat grubs if sampling shows enough of them to damage your turf, using the timing in our grub control guide. Do not treat the lawn just to fight the adults.

When to call a professional

Japanese beetles on garden plants are a DIY job for most people. A professional makes sense when:

• A large tree is being stripped every year and you cannot reach the canopy.
• You are considering a soil treatment for a tree. A certified arborist can judge whether it is warranted and how to keep it away from plants bees visit.
• Grub damage in the lawn is widespread and you want help with sampling and timing.

Ask any company which active ingredient they plan to use, whether it is toxic to bees, and how they will avoid treating plants in bloom. Our guide to choosing a pest control company has more questions to ask. For other garden problems, start with the lawn and garden pest guide.

Japanese beetle questions

Should I get rid of my roses? Not necessarily. Daily hand-picking and netting during the peak weeks can keep roses looking decent. In heavy beetle areas, mixing in less-favored plants helps.

How long will they be around? Peak feeding lasts about four to six weeks from late June. Damage drops off as the adults die in late summer.