How To Get Rid Of Japanese Beetles

Though basically harmless to humans directly (they don’t bite and aren’t poisonous despite having prickly bodies that can feel like a little pinch), Japanese beetles can completely ravage landscapes and crops. This can ultimately lead to unsightly lawns and, far worse, inedible fruits and vegetables.

A gardening blogger named Bonnie Blodgett from Minnesota described her struggle—nay, all-out war—with Japanese beetles:

“I blew it big-time last week,” she said. “Never make the mistake of suggesting that there is a limit to what a Japanese beetle will eat.” She apparently assumed that just because Japanese beetles hadn’t yet eaten her birch trees, that meant those trees (and other trees like them) were resistant to pesky, hungry beetles. The beetles love birch trees, and they’ll eat just about any sort of plant. “Based on your (the readers) descriptions,” she said, “I am now pretty well convinced that if it’s hungry enough a Japanese beetle will even eat me.”

Blodgett went on to describe how humans have played such a big role in the transportation of the beetles to the U.S. in the first place, then out west, where the habitats aren’t exactly conducive to the beetle population. So how did this Japanese beetle get over to the United States, and what the heck is it still doing here?

The Japanese beetle, as the name certainly implies, is native to Japan. Like many insects from all over the world, it was introduced to the United States through the shipping industry. Legend has it that this version of the beetle made its way to the States in a shipment of iris plants from the Land of the Rising Sun in the 1910s. It was first discovered in the bowels of a nursery in Riverton, New Jersey—a city close to Philadelphia—in 1916, meaning the beetles were most likely here at least couple years before that.

Since then, the Japanese beetle has permeated most of the remaining 50 states. The worst infestations are in states bordering the Mississippi River and states east of it, including Georgia, Tennessee, Ohio, and North Carolina.

There have also been partial infestations in:

There have been sightings of Japanese beetles as far west as Portland, Oregon, too, though the climate of many states out west aren’t ideal for the beetles’ survival.

Japanese beetles are pesky, somewhat-menacing little suckers. They emerge in their adult stage with a metallic green body and copper wings, which they use to fly from plant to plant.

The beetles are known to wreak havoc on plants, vegetations, and lawns all over the eastern United States, and they do so only being about half an inch long in their adult stages. Once they are adults, they do their damage in a life span that lasts about a month to a month and a half.

Adult female beetles lay eggs often in their short lifespan, laying up 60 eggs in a 45-day period, the entomology department at the University of Kentucky found. The eggs are laid during the afternoon hours a couple inches under the soil in June and July, and they hatch a couple weeks later. This then starts a lengthy period of living underground and feeding on the roots of grass and turf.

Known as “white grubs,” the recently hatched larvae of Japanese beetles grow in the soil for much of the winter. They hibernate during many of the cold months, too, diving further underground for warmer environments. Once the weather and soil get warmer, the larvae start to elevate back to the surface and enter the pupa stage, a four- to six-week period of feeding as an almost-hatched beetle before they emerge in June as adults.

Japanese beetles are known to feed on around 300 types of plants, according to the University of Kentucky. Some of the general types of plants the beetles use as fuel while living both below and above ground include:

Trees

Specific species of trees the beetles like are maple, birch, crabapple, and cherry. The beetles are known to stay away from oak and evergreen trees, another reason outside of climate as to why beetles don’t usually reside in the Pacific Northwest.

Vegetation

Beetles love feeding on crops, which is part of the reason why they’re so devastating in certain areas. The beetles feed on plants that host produce such as blueberries, raspberries, tomatoes, peppers, and grapes, just to name a few. They also feed on other vegetables and food including corn, carrots, plantains, beans, and asparagus. This is why Japanese beetles can be devastating to farmers.

Flowers

Japanese beetles are also attracted to plants like roses, poison ivy, morning glories, and lilacs because of their sweet, attractive smell. This affects our lawn and garden appearance in addition to affecting the surrounding environment.

Many of these plants are affected while the beetles are living above ground in their adult stage. While below the surface, mobility is limited, so the beetles feed on the roots of grass and turf near where the females lay the eggs.

The reason so many Japanese beetles can thrive and do damage in the United States is because of a combination of factors: the absence of natural predators and the amount of matter for them to feed on. The U.S., especially the areas in the eastern part of the country, has plenty of grass and crops for beetles to gnaw at.
There are plenty of animals and other insects around that help keep the beetle population at bay the best they can. Some of the beetle predators include:

• Birds, such as cardinals, grackles, and starlings
• Fowls, such as chickens, duck, and geese
• Spiders
• Racoons
• Moles
• Toads

The issue for many of these predators, though, is the predators can sometimes do more damage to grass and plants than the beetles and the grubs themselves. That’s because they have to dig and scratch around to find them! The College of Agriculture and Natural Resources at the University of Maryland said you should “keep working towards conserving natural enemies to help their populations ‘catch up’ to and suppress Japanese beetle densities.” So while you work to keep predator populations high, your best bet is to try and eliminate Japanese beetles from your yard yourself or with professional services.

The problem with beetles is that the mere presence of a beetle on a plant attracts even more beetles to the plant. It’s like a snowball picking up steam and getting bigger while rolling down a hill, only the snowball is the swarm of beetles and the objects in the snowball’s path are your crops. There are multiple suggested methods—both with hands-on maintenance and chemicals—that will help rid your yard of the beetles and do your best to make sure they don’t affect your area in the future.

Milky Spore

One of the most effective methods was developed way back in the 1930s and distributed to states over the next couple decades. Japanese beetles are susceptive to a disease called milky spore, so researchers decided it’d just be easiest to give the diseases to the beetles—especially in their grub stage before the fully develop into flying adults.

Known in the scientific world as Paenibacillus popilliae, milky spore can be purchased at any basic home improvement store. It’s advised you apply the spore—a white, powdery substance—to your lawn once per year, either in the spring or the fall, for three years. The disease will spread throughout the beetle population and help provide a long-term solution. It’s also suggested you apply the spore along with a nematode, which will help spread the disease quicker into the beetles.

Chemicals/Oils/Mixtures

Other solutions to help kill off beetles include chemicals and oils such as the following:

• Neem oil: This oil comes from trees and is non-toxic. You can spray it on roses and other plants that beetles enjoy eating. When male beetles ingest the oil, they’ll pass it along to the eggs. The hatched larvae will then eventually die before it becomes an adult thanks to the oil. Because of the importance of passing it onto the eggs, you should spray the oil just before the beetles enter their adult stage. That way, when the beetles do come above ground, they’ll consume the oil before mating.
• Insecticides: Insecticides that are specific for Japanese beetles help by attacking the nervous system of the pest. Certain chemicals may or may not be approved in your area, so research what types of sprays are the most effective near you. These sprays should be applied in the morning before the sun fully rises and the beetles are active again.
• Water-soap solution: This solution is harmless to the environment and can help suffocate beetles if applied correctly. Mix a quart of water with a teaspoon of dish soap. Then, put the solution into a spray bottle and apply it to any plants affected by the beetles. There are other viable additions to the solution like oils and rubbing alcohol, depending on the plants you have in your area.

Some of these applications may be harmful to other species in your environment, so it’s important to do the proper research for how these chemicals and oils could affect the plants and animals around you. For example, Neem oil is harmful to fish, so don’t apply the oil near ponds or areas where a storm could create runoff to a source of water.

Row Covers

If you don’t notice beetle damage until the summer, when they start to blossom into adults and start feeding above ground, row covers should help. You should use row covers just during the Japanese beetles’ above-ground feeding period, which starts around mid-June and lasts for about six-to-eight weeks.

Some methods that are suggested can have adverse effects if they’re not done correctly or in specific situations. Just like how the presence of certain natural predators can make the problem worse, there are certain methods that can have reverse effects on both your landscapes and the amount of beetles you have in your yard.
For example, some sources advise you set attractants and pheromone traps to help lure male beetles toward traps and ultimately kill them. Applications like this only work if you have a big enough yard to lure the beetles away from. If you lay these traps in a confined space, it only invites more beetles to the area. There are also some natural deterrents to beetles like garlic and chives. The smell of these plants is highly unattractive to Japanese beetles. Make sure to surround the susceptible plants with the natural deterrents so the beetles don’t have a way into the area.

If you have taken the above advice but continue to find Japanese beetles in your yard, garden, and similar areas, it’s very likely that you have an infestation. To best deal with this, you should call in the professionals and let them fix the problem for you.