How to Get Rid of Japanese Beetles in the Garden (2024)

Catherine Boeckmann

April 18, 2024

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. Here are 10 tips to preventbeetles:

1. 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 Japanese Beetle grubs before they become destructive adults. The grubs ingest the spores as they feed in the soil. It is as effective as a chemical pesticide but NOT toxic to beneficial insects, such as bees and pollinators; it will not harm people, pets, animals, or plants. Once ingested, BTG kills grubs for several weeks, during the time they are most active.
   
2. Hand pick 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’stime-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.
   
3. Protect 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.
   
4. Spray Neemoil if early: 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.
   
5. Do NOT use 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.
   
6. Choose the right plants: There are some that Japanese Beetles seldom damage, such as boxwood, clematis, chrysanthemum, conifers, daylily, geranium, ginkgo, Japanese tree lilac, forsythia, common lilac, magnolia, red and silver maple, oak, white poplar, redbud, rhododendron, and yew. See our list of theBest and Worst Plants for Japanese Beetles. Dispersing the beetle’s favorite plants throughout the landscape, rather than grouping them together, can also help.
   
7. 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.
   
8. 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), Russian sage (Perovskia), lavender (Lavandula), yarrow (Achillea), oregano (Origanum), catmint (Nepeta) and calamint (Calamintha). 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.
   
9. 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 two to four 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 plantsis necessary during the bloom period, do not apply during hours when bees are visiting the flowers (late morning through mid-day). 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.
   

10. Nip rose buds and spray rose bushes: Note that insecticideswill not fully protect roses, which unfold too fast and are especially attractive to beetles. When beetles are mostabundant on roses, nip the buds and spray the bushes to protect the leaves. When the beetles become scarce, let thebushes bloom again. Timeliness and thoroughness of application are very important. Begin treatment as soon as beetlesappear, before damage isdone.

For rose growers, see ourGrowing Guide for Roses for more tips on caring forroses!

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