How To Get Rid Of Japanese Beetles | The Old Farmer's Almanac

How to Kill Japanese Beetles

To manage Japanese Beetles in yards and gardens, the trick is to start early! Once these insects are present in large numbers, the problem is very difficult to manage.

Consider BTG or Bacillus thuringiensis galleria

Start at the grub stage! BTG or Bacillus thuringiensis galleriae (e.g., products such as grubGONE!) uses naturally occurring soil bacteria. This bacillus ONLY targets certain lawn insect pests, such as Japanese Beetle grubs, before they become destructive adults. The grubs ingest the spores and the natural yet powerful BTG proteins as they feed in the soil. It is as effective as a chemical pesticide and works within days to weeks of application, but is NOT toxic to beneficial insects, such as earthworms, bees, and pollinators; it will not harm people, pets, animals, or plants. BTG will kill not only Japanese Beetle grubs but also a variety of other destructive beetle larvae and grubs, such as chafers, oriental beetles, and billbugs, throughout the spring through fall seasons.To deter an infestation of adult beetles and kill the beetles that do infest your edible or ornamental plants, you can use BTG as a spray (e.g., product beetleGONE!). Like with the grubs, BTG effectively kills the adult beetles through a combination of the BTG protein and spores. One key to success is to start applying early: at the first signs of the adult beetle. Farmers and growers have stated that they believe BTG may reduce the attraction by early-arriving beetles of more beetles by inhibiting the effectiveness of the early arrivals’ use of their beetle-attracting pheromones. This product can be mixed in water and sprayed on edible garden plants, ornamental plants, and trees to kill Japanese Beetle adults or put into turf to kill the grubs. It can also be used dry as a mix into potting or garden soil to control beetle grubs. The product is registered with a zero-day pre-harvest interval, therefore, you can treat for beetles and pick your food the same day. There are no label restrictions for use around bees or flowering plants; therefore, it can be safely used while pollinators are active. There is also no toxicity to fish or aquatic life.

Handpick Early

Look for beetles in mid- to late June or early July. In the early morning or evening, when beetles are more sluggish, knock beetles into a bucket of soapy water. Yes, it’s time-consuming, but it’s also the most effective way to kill these pests. Just be diligent. When you pick them off, put them in a solution of 1 tablespoon of liquid dishwashing detergent and water, which will cause them to drown. Do this daily, as the chemical trail of beetles attracts more beetles.

Introduce Natural Enemies

You can also attract native species of parasitic wasps (Tiphia vernalis or T. popilliavora) and flies to your garden, as they are predators of the beetles and can be beneficial insects. They will probably attack the larvae, but they are not very effective in reducing the overall beetle population.

Spray Neem Oil

Deter feeding by adult beetles by spraying plants with neem oil, which contains potassium bicarbonate. Adult beetles ingest a chemical in the neem oil and pass it on to their eggs, and the resulting larvae die before they become adults. Neem oil is effective for several days, but repeat applications are needed, especially after rainfall. Neem oil is not effective once you have beetles in large numbers. Neem is low risk to bees and other beneficial insects but can be harmful to fish and aquatic life, so don’t use it near lakes, rivers, and water.

Consider Insecticides

Beware of insecticides. If you wish to use insecticides, speak to your local cooperative extension or garden center about approved insecticides in your area, and be aware of whether you’re killing the very pollinators that bring fruit and flowers!For example, Chlorantraniliprole (Acelepryn®) provides 2 to 4 weeks of protection and is low risk to bees. But most dusts or sprays are highly toxic to honeybees, native bees, and other pollinators. If application of these materials to plants is necessary during the bloom period, do not apply during hours when bees are visiting the flowers (late morning through midday). Apply sprays in the morning, never in full sun or at temperatures above 90ºF. If your plants start to wilt, rinse the leaves immediately with clean water.

Nip Rose Buds and Spray Rose Bushes

When beetles are most abundant on roses, nip the buds and spray the bushes to protect the leaves. When the beetles become scarce, let the bushes bloom again. Timeliness and thoroughness of application are very important. Begin treatment as soon as beetles appear, before damage is done. For rose growers, see our Growing Guide for Roses for more tips on caring for roses!

Japanese Beetle Prevention

Choose the Right Plants

There are some plants that Japanese Beetles seldom damage, such as boxwood, chrysanthemum, clematis, conifers, daylily, forsythia, geranium, ginkgo, common lilac, Japanese tree lilac, magnolia, red and silver maple, oak, white poplar, redbud, rhododendron, and yew. See our list of the Best and Worst Plants for Japanese Beetles.

Dispersing the beetle’s favorite plants throughout the landscape, rather than grouping them together, can also help.

Protect Your Crops With Row Covers

Use row covers during the 6- to 8-week feeding period that begins by mid- to late June in the North and mid- to late May in the South. Row covers will keep the pests out, but they will keep pollinators out, too; be sure to remove netting or covers if your crops need to be pollinated. Do not cover plants in bloom that require pollination (i.e., fruits); after the plant sets fruit, then cover it with netting.

Use Companion Plants

Avoid attracting beetles with companion planting. Try planting garlic, rue, or tansy near your affected plants to deter Japanese beetles. (Roses love garlic is a popular expression.) All herbs and other aromatic plants make wonderful companions. Scented geraniums (Pelargonium), rue (Ruta), feverfew (Tanacetum), parsley (Petroselinum), and thyme (Thymus) all may help ward off Japanese beetles as well as aphids.

Try ornamental and culinary sage (Salvia), anise-hyssop (Agastache), calamint (Calamintha), catmint (Nepeta), lavender (Lavandula), oregano (Origanum), Russian sage (Perovskia), and yarrow (Achillea). Four-o’clocks (Mirabilis) and larkspur (Delphinium) are said to act as decoys by attracting rose-loving Japanese beetles to eat their poisonous leaves, but they do not kill the beetles.

Methods That Don’t Work

Japanese Beetle Traps

Do NOT use Japanese Beetle traps. They attract beetles, but research has proven that more beetles fly toward the traps than are caught. You’ll be pulling beetles in from all over town and end up with a worse problem.

Neem Oil

While we mentioned Neem oil above as a solution, it is essential to note that it has a time and place. Once you have a large population of beetles, or once they have grown to full-size adults, Neem oil will no longer be effective.

FAQ

What spray kills Japanese beetles?

Insecticidal sprays containing carbaryl, pyrethrin, or neem oil are commonly used. Neem oil works best when applied early, as it disrupts the beetles’ feeding and reproduction. Always follow label instructions and reapply as needed.

When do Japanese beetles go away?

Adult beetles typically appear in late June and remain active for 4–6 weeks, usually disappearing by mid-to-late August.

Do Japanese beetles bite humans?

No. Japanese beetles do not bite or sting. They only feed on plants and are harmless to people and pets.

Do grubs turn into Japanese beetles?

Yes. The white C-shaped grubs found in soil are the larval stage of Japanese beetles. They feed on grass roots, overwinter in the soil, and then emerge as adult beetles the following summer.

What birds eat Japanese beetles?

Many backyard birds (including starlings, robins, cardinals, and crows) feed on Japanese beetles. Encouraging birds in your garden with feeders, water, or nesting spots can help reduce beetle numbers. Learn more about creating a bird-friendly garden.