The metallic green beetles that have made your garden their new home may look cool, but don’t be fooled by their flashy appearance. Japanese beetles are one of the most destructive landscape pests faced by homeowners, and can turn healthy plants into skeletal messes in a matter of days.
I knew it last week because my garden of beautiful, healthy zinnias that I started from seed were looking stunning and ready to bloom. this week? Almost all of the leaves have holes, and some have very little material left on them.
The Japanese beetle, which eats more than 300 plants, can quickly destroy your garden in a variety of ways.
“They attack plants from two directions,” says Ed Dorschun, vice president and technical director of Catch Master, a pest control brand used by professionals for more than 70 years and sold in retail stores nationwide. “Adults feed on leaves, flowers and fruits above ground, while larvae feed on grass roots in the soil and cause damage below the surface.”
Want to protect your garden before it’s too late? Here’s how to get rid of Japanese beetles and when you should contact a pest specialist.
What is Japanese beetle?
The Japanese beetle is a metallic green and brown beetle about 1/2 inch long. Commonly seen on sunny days, these flying beetles can be found feeding in groups in your garden.
“This is not a pest that sticks around in the corners of your garden and becomes even more destructive,” Druschun says. Japanese beetles are not picky eaters and happily eat more than 300 types of flowering and fruiting plants. Their favorites include roses, birches, maples, and fruit trees.
The Japanese rhinoceros beetle is an invasive species that has spread from the East Coast to the Midwest. Partial infestation extends into Colorado.
How to get rid of Japanese beetles
To get rid of Japanese beetles, you need to target both the adults and larvae underground.
The most effective, but labor-intensive, way to eradicate Japanese beetles is to pick the bugs from the plant with your bare hands and drop them into a cup of soapy water. You can also shake the branch to knock the beetles directly into the ground or into the cup.
For underground larvae, insecticides (such as chemical larvicides such as imidacloprid (GrubEx) or chlorantraniliprole) or natural products (such as the bacteria milky spores or beneficial nematodes that hunt and kill the larvae) must be applied to the soil.
The challenge is making sure to catch all the beetles and treating all areas where the larvae grow. Even one missed beetle can lead to a new infestation. “They’re also social feeders, which is why you often find them in groups,” says Dorschun. “When one beetle finds a plant it likes, it releases pheromones that attract more beetles to the same location.”
Why Japanese beetles invade gardens
Japanese beetles use gardens for food and lawns for laying eggs. These insects begin to be seen in May, but peak activity occurs in June and July in most areas.
“The season is short, but the damage window is intense,” says Dorschun. One day there may be no beetles, and the next day there may be hundreds, or even thousands.
Signs of Japanese beetle infestation
If you see one Japanese beetle, there are probably many more. But it’s also a tell-tale sign if the leaves look deteriorating.
“The first and easiest sign is usually the beetle itself,” Druschun says. “In plants, look for skeletal leaves with only the veins remaining, chewed petals on roses, grapes, fruit trees, basil, beans, etc., browned leaves, and beetles.”
“On lawns, brown spots that are easily pulled out can indicate larvae active beneath the soil,” Dorschun added.
Natural ways to get rid of Japanese beetles
You can get rid of Japanese beetles yourself, but you need to stay on top of the situation to continue your efforts.
“Start early and be consistent,” Druschun says. “If there are only a small number of beetles, the soapy water method is effective.”
Beetles move slower in the morning, so it’s easier to collect them. To get rid of them, shake the affected plants over a bucket of soapy water to swat the beetles. Large-scale invasions require more strategies such as trapping.
“In case of large-scale infestations, trapping is more practical,” Dorschun explains. Traps use some type of attractant, such as pheromones or floral scents. Traps should be placed away from the garden to draw the beetles away from affected plants. Check your traps regularly and empty them frequently.
Treatment of Japanese beetles by professionals
“Japanese beetles are not a one-day problem, so consistency is key,” Dorschun says. Additionally, if you are unable to continue regular trapping or daily collection, you may need professional help.
Pest control companies will spray your property, including Japanese hot spots such as trees and leaves. It also treats grass larvae. This acts as both treatment and prevention. Adults become extinct and their life cycle is destroyed.
How to prevent the return of Japanese beetles
“I’m cautious about calling any plant a true repellent,” Druschun says. “However, in areas with recurring beetle infestations, mixing in less desirable plants such as lilacs and magnolias can make the landscape less attractive.”
Plants that may deter Japanese beetles include:
- boxwood tree
- magnolia
- lilac
- chives
- actinidia polygama
- garlic
- lavender
If you have a garden full of plants that attract Japanese beetles, such as roses and grapes, you should be prepared to fight them on a regular basis. “The goal is to drive the beetles out of the garden, not to give them a strong reason to congregate there,” Druschun says. Avoiding these plants in future garden areas may be the right choice.
Common mistakes when trying to get rid of Japanese beetles
Controlling the Japanese beetle requires a multifaceted integrated pest management (IPM) solution, but there are many opportunities for failure in the process.
- Soil is not treated. Beetle larvae live in the soil and emerge as a new generation of Japanese beetles.
- Treating the soil at the wrong time. If the soil is treated too early, the treatment will not be effective. Treatment should be done in late summer or early autumn to allow the larvae to fully develop.
- Rely solely on pheromone traps. Traps act as powerful attractants and can attract more beetles than the trap can hold. Overflow can attack other plants.
- Leave the damaged leaves alone. Japanese beetles leave behind pheromones that attract more beetles. Remove damaged leaves to reduce damage.
When to contact a pest control professional
A pest control company can help you get rid of Japanese beetles and prevent them from coming back. If you have an active beetle infestation or if DIY methods aren’t working, call a professional.
FAQ
What instantly kills Japanese beetles?
Most insecticides are effective against Japanese beetles. You can also quickly kill it by slamming it into a bowl of soapy water.
Can Dawn dish detergent get rid of Japanese beetles?
Dawn dish soap and water can kill Japanese beetles, but the beetles must be shaken off infected branches to be effective.
Is it possible to permanently get rid of Japanese beetles?
Although effective prevention and treatment strategies can be developed against Japanese beetles, permanent eradication is impossible.
Why are there suddenly Japanese beetles?
Japanese rhinoceros beetles suddenly appear in midsummer when the larvae become adults. This stage of the life cycle occurs when soil temperature reaches 50 degrees.
