What Are Japanese Beetles and Why Are They in My Yard?

If creepy-crawlies give you the heebie-jeebies, you definitely want to be on the lookout for a Japanese beetle invasion. They may have a pretty metallic green appearance, but these little insects have a big appetite for destruction.

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What Are Japanese Beetles?

Japanese beetles are an invasive species in the United States. Only about 7/16 inches long, these pests display metallic green bodies with bronze-colored wings and six tufts of white hair under the edges of their wings. Japanese beetle grub larvae have white or cream bodies and tan heads.

Eggs are laid underground. The Japanese beetle grub larvae spend the winter underground until spring, when they move closer to the surface. By the end of June or beginning of July, the adults emerge from the ground and start their path of destruction.

Why Are They in My Yard?

Most states in the eastern and central parts of the United States have Japanese beetles. If you live in those areas, you could find a Japanese beetle infestation in your yard no matter what. Your yard is often more tempting if it's full of plants for the beetles to enjoy. They eat grass, flowers, trees, leaves, fruit and other parts of plants.

Once a few beetles make it into your yard, more are sure to follow. The scent they leave behind attracts more Japanese beetles to your yard. Controlling the population once you notice you have a problem is important to prevent more from following.

Are Japanese Beetles Harmful?

Japanese beetles aren't harmful to humans. They don't bite like mosquitoes do. However, if you have dogs that spend time outdoors, they could encounter some issues. Dogs that eat a lot of Japanese beetles could have digestive issues. The pests also release hemolymph when they're attacked. This chemical is corrosive, so it could cause chemical burns on your dog. Fortunately, they don't taste or smell great, so your dog likely won't eat too many.

Will Japanese Beetles Damage My Garden?

Your plants and trees, however, often fall victim to the destruction of Japanese beetles. Larvae eat the roots of your lawn while they're underground, which results in dead brown spots. When they get older, the beetles munch on leaves, fruit and flower petals, often to the point of turning the plant parts into skeletons.

Mature plants and trees can often withstand the Japanese beetle attack. They might not look great, but they typically survive. Younger plants that aren't established and strong may experience growth issues or die completely. While your flowering plants might survive, the blooms themselves are destroyed. Fruit and vegetable plants might experience a smaller yield if you have a Japanese beetle infestation.

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How Do I Kill Japanese Beetles?

Monitoring your yard and dealing with Japanese beetles early is your best defense. If you can catch the issue when you have just a few, you can eradicate them before they attract hordes of additional pests with their scent.

Here are some options for eliminating these insects:

Hand-Picking

You can manually remove the beetles from your plants. Pick them up with a gloved hand or shake them off the plant into a container of soapy water to kill them.

Japanese Beetle Spray

Contrary to what you might think, commercial insecticides aren't your only option. In fact, insecticides may actually aggravate the problem, by increasing the scent that attracts more beetles.

Make a simple Japanese beetle spray by mixing dish soap with water in a spray bottle. Spray it on your plants to repel the beetles.

Neem Oil

If the infestation is still small, spraying neem oil on the plants can help. It works by killing the larvae that the adults lay to keep the problem from continuing.

Natural Predators

Encouraging natural predator insects — such as parasitic wasps and nematodes — can allow for natural removal of the beetles.

Japanese Beetle Traps

Traps come with mixed reviews, so use them with caution. This option may attract more beetles to your yard. If you use Japanese beetle traps, monitor the overall activity in your yard to see if it increases or decreases.

How Do I Keep Japanese Beetles From Coming Back?

While you can't completely prevent a future Japanese beetle infestation, you can minimize your risks by watching for new infestations closely. Hand-pick them quickly to keep more from entering your yard.

Another option is planting varieties of plants that Japanese beetles don't like. Examples include scallions, catnip, geraniums, daylilies, lilacs and garlic. Try planting these options between other varieties that the beetles eat regularly, or plant them around the perimeter of your yard.

Focus on Japanese beetles at the grub stage by using an insecticide product containing Bacillus thuringiensis galleriae, which are bacteria that naturally occur in soil. It specifically targets pests without hurting pollinators. By killing the grubs, you can avoid the harmful adult stage.