How to control Japanese beetles

Japanese beetles (Popillia japonica) are a common lawn and garden pest each summer in Ohio, east of a line running from Cleveland to Cincinnati, according to Ohio State University Extension. They can be found in western parts of Ohio, too, as well as east of Wisconsin, Michigan, Illinois, south to Alabama and into states as far west as Colorado.

What do Japanese beetles look like?

Japanese beetles are ⅜-inch long and ¼-inch wide insects with copper-colored wings and metallic green heads. They can be identified by the five white tufts of hair along their bodies. Males are identified by a sharp tip on their foreleg tibia. Females are identified by a long, rounded tip on their foreleg tibia.

Related: How to manage insects in the garden

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There are other beetles that resemble Japanese beetles. University of Minnesota Extension has photos of those beetles, including rose chafers and May/June beetles.

Japanese beetle larvae are known as white grubs. White grubs will eat seedling plants and damage turf by feeding on grass roots, which reduces the ability for grass to take up enough water to survive during hot and dry weather and thus causes grass to die, according to University of Minnesota Extension. The grass can be rolled back, exposing the grubs and lack of roots. Some bird and animals, like crows, moles and skunks, feed on grubs, so you may see them digging up turf and damaging it further.

Which plants do Japanese beetles eat?

Japanese beetles feed on as many as 400 species of broadleaf plants.

Ohio State University Extension lists the plants, trees and shrubs most-susceptible to Japanese beetle damage:

• Birch
• Cherry
• Elms
• Horse chestnut
• Japanese maple
• Lindens
• Mountain ash
• Norway maple
• Ornamental apple
• Pin oak
• Plum
• Rose
• Rose of Sharon
• Sycamore
• Virginia creeper
• Willows

Trees and shrubs that Japanese beetles usually don’t attack include:

• Arborvitae
• Ashes
• Boxwood
• Cedar
• Euonymus
• Flowering dogwood
• Forsythia
• Holly
• Hydrangeas
• Juniper
• Lilacs
• Magnolias
• Privet
• Red maple
• Red mulberry
• Red oak
• Silver maple
• Spruces
• Tulip tree
• Yews

The good news: Japanese beetles usually don’t kill plants, but they are skeletonizers. University of Illinois Extension explains that Japanese beetles will eat the leaves, flowers and fruits, leaving just the leaf veins. Also, Japanese beetles prefer plants in full sun locations and are most active on warm, sunny days.

At-home remedies for Japanese beetles

The Old Farmers’ Almanac says to mix 1 teaspoon liquid dishwashing detergent and 1 cup vegetable oil, then shake well. Add the mixture to 1 quart of water, then add 1 cup rubbing alcohol and shake again. Using a spray bottle, apply to plants with Japanese beetles every 10 days. Keep in mind that homemade sprays may damage your plants.

The Old Farmers’ Almanac also suggests placing geraniums close to plants that you don’t want Japanese beetles to destroy. Japanese beetles are attracted to geraniums, and once they feed on the flowers, they will get dizzy and drop to the ground.

How can I control Japanese beetles in my lawn and garden?

As pesticide sprays like Sevin can effectively reduce Japanese beetle damage for up to two weeks, they are toxic to beneficial insects like bees, University of Illinois Extension.

Here are some other control methods to try:

Traps
Japanese beetle traps — whether nets, jars or bags — have been ineffective in making a significant impact on the beetle population in heavily-infested areas. Actually, University of Iowa Extension explains, research has shown that the traps may actually attract more beetles. However, if you live in a lightly-infested area, traps may work to alleviate Japanese beetle problems on your property.

Habitat modification

Ohio State University Extension suggests planting trees, shrubs and plants that are not usually targeted by Japanese beetles in order to avoid damage to landscape plants.

Biological controls

Ohio State University Extension says that commercially-available products containing entomophagous nematodes can be somewhat effective when applied while grubs are in the second instars, along with irrigation before and after application.

Chemical controls

Ohio State University Extension recommends preventative and curative insecticides. This fact sheet explains which chemicals are effective and when chemicals should be applied.

How do you control Japanese beetles on your lawn and in your garden? Tell us in the comments below.

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