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If you spot a little creature with a metallic green body and copper-colored wings in your garden, you have likely met the Popillia japonica, commonly known as the Japanese beetle. Japanese beetles might seem enchanting at first glance, but their insatiable appetite poses a serious threat to gardens and landscaping. Below, we’ll explore how to get rid of Japanese beetles and how to keep them away.
Causes of Japanese Beetle Infestations
Japanese beetles were first discovered stateside in New Jersey in 1916 but have since spread throughout the Eastern, Southern, and Midwestern regions. Natural predators keep Japanese beetle populations in check in their native Japan, but the pests have proven to be a hassle in the United States.
Life Cycle of Japanese Beetles
The life cycle of Japanese beetles includes four stages: egg, larva, pupa, and adult. The process begins when females emit pheromones to attract a mate, and once the beetles breed, they tunnel underground to lay eggs in the soil. Roughly two weeks later, the eggs hatch into Japanese beetle larvae, which are C-shaped white grubs that feast on grass roots, creating visible brown patches on your lawn.
Adult Japanese beetles emerge from the ground in late June or early July and feed throughout the summer. Japanese beetle grubs remain in the soil throughout the winter, resuming their activity and growth as temperatures warm up in the spring.
Preferred Food Sources
Japanese beetles are highly mobile and can fly several miles in search of food. Once a beetle finds a plant that is palatable, it will produce a floral scent that attracts others. As a result, infestations spread quickly, making Japanese beetles a challenging pest to eradicate.
Adult Japanese beetles eat more than 300 different species of plants and are especially attracted to fragrant flowers. Preferred plants include the following:
- Corn silks
- Green bean
- Virginia creeper
Japanese beetles also damage birch, crape myrtle, elm, horse chestnut, linden, maple, mountain ash, sassafras, and sycamore trees.
Risks of Japanese Beetle Infestations
Americans spend more than $460 million a year to control and recover from damage caused by Japanese beetles, according to the USDA. About a third of that is spent on replacing turf damaged by Japanese beetle grubs.
Mature trees and shrubs can survive Japanese beetle infestations without suffering long-term damage, but young or unhealthy plants may be stunted or killed, and beetles will ruin the blossoms of even the healthiest flowering plants. Japanese beetles frequently cause full or partial defoliation, leaving behind lacy skeletonized leaves.
Homeowners will likely notice damage inflicted by grubs, which chew through grass roots and leave behind dead patches of grass that can be rolled back like a carpet.
Methods of Japanese Beetle Control
Controlling Japanese beetles can be a delicate process because homeowners must avoid harming pollinators and plants during the eradication process. Below are a few safe and effective options for addressing a Japanese beetle infestation.
If you prefer a natural DIY approach to protecting your garden, consider the following:
- Biological controls: As a natural alternative to insecticides, you can introduce beneficial parasites and bacteria to your lawn and garden. For example, beneficial nematodes, an insect-eating roundworm, actively seek out Japanese beetle grubs in the soil.
- Hand-picking: If your garden is relatively small, you can simply remove individual beetles from your plants. Check plants daily in the morning or evening when beetles are more sluggish, and knock the pests into a bucket of soapy water to kill them.
- Natural insecticides: Finding insecticides that are organic is tricky but not impossible. Neem oil is one effective method and poses little risk to bees and other beneficial insects. Apply it to the leaves of affected plants in the beginning stages of an infestation using a spray bottle, and reapply every few days.
- Plant covers: Covering plants with a physical barrier will prevent Japanese beetle damage. Use nets or row covers to protect fruit trees and other plants after they are done blooming. Timing is crucial, though, because if you cover plants too early in the season, pollinators will not be able to reach them.
Commercial and Professional Remedies
If DIY control methods prove insufficient, commercial products and professional pest control companies may be able to help. Here are a few options:
- Commercial pesticides: You can find a wide variety of targeted and broad-spectrum insecticides that repel or kill Japanese beetles. Some insecticides are toxic to pollinators and other beneficial insects, so read directions carefully.
- Japanese beetle traps: Japanese beetle traps available from Amazon or your local garden center use pheromones or floral scents as bait. These traps catch and kill large numbers of Japanese beetles.
- Professional pest control: Licensed exterminators such as Orkin or Terminix have access to products that are not commercially available to homeowners. They also have the tools and expertise to tackle a wide range of pest problems.
How to Prevent Future Japanese Beetle Infestations
Start hand-picking beetles the moment you notice them or apply an appropriate repellent to affected areas. Make sure your lawn is well-watered and well-drained, as healthy soil will help counteract the stress caused by grubs. Do the same for trees to guard against damage from adult beetles. Apply physical barriers during peak beetle season after plants have begun sprouting fruit.
You can also lure Japanese beetles away from your garden by planting trap crops, such as geraniums and borage, the former of which are attractive and toxic to Japanese beetles. Finally, try companion planting, or incorporating plants Japanese beetles dislike, such as catnip and garlic, into your garden.
Between home remedies and professional pest control services, gardeners have plenty of options to combat Japanese beetle infestations. By addressing an infestation early and taking preventive steps, you can minimize the damage caused by these voracious insects.
How to Get Rid of Japanese Beetles FAQ
Does Dawn dish soap repel Japanese beetles?
If you mix a few tablespoons of Dawn dish soap with water, you can spray the solution on individual beetles to kill them. You can also apply the solution directly to plants to help repel beetles.
What is the best way to kill Japanese beetles?
The best way to kill Japanese beetles is to manually remove them from plants and drown them in a bucket of soapy water. Neem oil and certain chemical insecticides can also be effective but may also harm beneficial insects.
What do Japanese beetles hate?
Like many insects, Japanese beetles seem to hate the scent of plants in the allium and mint families, including garlic, onions, catnip, and peppermint.
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