Here are tips on how to identify and get rid of Japanese beetles.
What are Japanese Beetles?
Japanese beetles are small bugs that carry a big threat. They do not discriminate on what types of plants to feed on, in fact, they are classified as a pest to hundreds of different species. They are one of the most major insect pests in the Eastern and Midwestern US, causing monumental damage to crops each year. Native to Japan, they were first documented in the US in 1919, and have since spread across the country.
How to Identify Japanese Beetles
Japanese Beetles are ½ inch in length and metallic blue-green with tan wings, with small white hairs lining each side of the abdomen. They lay eggs in the soil during June, which develop into tiny white grubs. These grubs will remain under wraps for about 10 months and overwinter and grow in the soil. They emerge from the soil as adult beetles and begin feeding in June. They usually attack plants in groups, which is why damage is so severe. Although the lifecycle of the adult Japanese beetle is barely 40 days, it can cover a lot of ground. Look for leaves that are “skeletonized” (only have veins remaining). This is a tell-tale sign of Japanese Beetles. Mexican Bean Beetles can also leave foliage skeletonized, though, so be sure to identify them by their appearance as well.
How to Get Rid of Japanese Beetles
- Try to select plants that Japanese Beetles will not be attracted to. See our list of Best and Worst Plants for Japanese Beetles.
- Good horticultural practices, including watering and fertilizing, will reduce the damage caused by these beetles.
- In the grub stage of late spring and fall (beetles have two life cycles per season), spray the lawn with 2 tablespoons of liquid dishwashing soap diluted in 1 gallon of water per 1,000 square feet. The grubs will surface and the birds will love you. Spray once each week until no more grubs surface.
- Unfortunately, the most effective way of getting rid of Japanese beetles is to hand pick them. It's time consuming, but it works, especially if you are diligent.
- You can also purchase parasitic nematodes (most garden centers have them) and drench the soil around the area where you have the problem.
- Neem oil and sprays containing potassium bicarbonate are somewhat effective.
- Put down a dropcloth and, in the early morning when they're most active, shake them off and dump them into a bucket of soapy water. They will not survive.
- If you wish to spray or dust with insecticides, speak to your local cooperative or garden center about approved insectitudes in your area.
- Beetles on Roses? Note that insecticides will not fully protect roses, which unfold too fast and are especially attractive to beetles. 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.
NOTE: Many dusts or sprays are highly toxic to honeybees. If application of these materials to plants is necessary during the bloom period, do not apply during hours when bees are visiting the flowers. If larger than yard and garden plantings are to be treated, you may need to contact nearby beekeepers in advance so that they can protect their colonies.