The Japanese beetle, scientifically known as Popillia japonica, is a well-known insect species famous for its vibrant metallic green and copper-colored outer shell. Originally from Japan, this beetle is notorious for its invasive behavior and harmful eating patterns. Ever since it was unintentionally brought to the United States in the early 1900s, the Japanese beetle has emerged as a major pest, wreaking havoc on various ornamental plants, fruits, vegetables, and crops. In this blog, we will explore the characteristics, life cycle, feeding habits, and control methods associated with the Japanese beetle.
Are Japanese Beetles Harmful?
Many people admire the striking appearance of the Japanese beetle, yet many are unaware of its destructive nature. These pests are notorious for their feeding habits and can cause substantial damage to various plants and crops. Here are some key reasons why the Japanese beetle is considered a pest and a threat to the environment.
Destructive Feeding Habits Lead to Severe Plant Damage
Adult Japanese beetles feed on a wide range of plants, including ornamental flowers, fruit trees, vegetables, and field crops. They are aggressive feeders, consuming the tissue between the veins of leaves, which creates a distinctive "skeletonized" appearance. Beyond the unsightly look, their feeding can cause severe damage to plants, reducing photosynthesis and stunting growth. This weakens the plants, making them more vulnerable to diseases, environmental stressors, and other threats. In agricultural settings, Japanese beetles can lead to significant economic losses by damaging crops like grapes, corn, soybeans, and various fruits, affecting both the quality and quantity of the harvest.
Japanese Beetles are an Invasive Species
Japanese beetles are not native to North America, having been accidentally introduced in the early 20th century. Since then, they have spread across much of the continent. As an invasive species, Japanese beetles can disrupt local ecosystems by outcompeting native insects for food, which can upset the ecological balance and negatively affect native plants and insect populations.
Japanese Beetles Cause Damage Throughout Each Stage of Life
Japanese beetles affect plants in more than just their adult stage. The larvae, known as grubs, live in the soil and feed on plant roots, often damaging grass and turf. This root damage can cause unsightly brown patches in lawns, leading to both economic and aesthetic concerns for homeowners and landscapers.
Resistance To Control Methods
Japanese beetles have gradually developed resistance to some insecticides, making their control increasingly difficult.
Makes Plants more Vulnerable to Other Pests/Diseases
The feeding activity of Japanese beetles creates wounds on plants, providing entry points for pathogens. The resulting weakened state of the plant also makes it more vulnerable to other pests and diseases.
What Do Japanese Beetles Look Like?
Japanese beetles are easily identifiable due to their distinctive features. Adults are about half an inch long with a metallic green body and coppery-brown wing covers, or elytra, which give them a glossy appearance. The elytra are adorned with small white hair tufts on the sides, creating a dotted pattern visible from certain angles. The beetle’s shiny, metallic green head has prominent white tufts extending backward, and their short antennae end in a club shape. Their long legs, which can appear black or metallic green, and their oval, slightly flattened shape add to their distinct look. When resting, their elytra cover their wings, giving them a turtle-like appearance. Although variations can occur, with older or environmentally stressed beetles sometimes appearing slightly brownish or less shiny, these features generally make the Japanese beetle easy to recognize.
How to Get Rid of Japanese Beetles: 12 Tips
Japanese beetles can be quite troublesome and challenging to eliminate. If you're dealing with these pests in your lawns, landscapes, or gardens and are seeking ways to address them, here are some methods you can use to manage and control their population.
1. Remove Them from Your Plants by Hand
Early in the morning, when the beetles are less active, go outside and manually remove them from your plants. Place them in a bucket of soapy water to kill them. While this is not very effective for large populations, it works quite well if you are only noticing a few on your plants here and there.
2. Cut Back Affected Areas
Remove any heavily infested foliage to decrease the attraction of beetles to your garden. This will not only eliminate beetles feeding on those parts but also allow your plants to redirect their energy toward new growth rather than attempting to maintain damaged leaves.
3. Use Neem Oil
Neem oil is a natural insecticide that interferes with beetles' feeding and reproduction. Follow the instructions on the label and apply it to any affected plants.
4. Have You Heard of beetleGONE?
BeetleGONE! is the first bio-insecticide with Bacillus thuringiensis galleriae (Btg) designed to control adult beetles with the same effectiveness as chemical products. Unlike chemical options, this product avoids negative side effects and is safe for beneficial insects.
5. Release Beneficial Nematodes
Beneficial nematodes are tiny microorganisms that can be introduced into your soil to target and eliminate Japanese beetle larvae. They are eco-friendly and pose no harm to other beneficial insects.
6. Use Insecticidal Soap
Insecticidal soaps can be applied directly to Japanese beetles. This insect control product works by disrupting the pests' cell membranes and causing suffocation.
7. Try Pyrethrin-based Insecticides
Pyrethrin-based insecticides, made from chrysanthemum flowers, can be effective in controlling Japanese beetles. Be sure to follow the product label instructions for best results.
8. Introduce Natural Enemies of the Japanese Beetle
Paenibacillus popilliae, known as Milky Spore Disease, is a bacterial pathogen that targets Japanese beetle larvae. Applying milky spore powder to your lawn can help manage these larvae. Another natural enemy, Istocheta aldrichi (Tachinid fly), lays its eggs on adult beetles; the larvae then burrow into and kill the beetle. Tiphia vernalis, a parasitic wasp, deposits its eggs on late-stage grubs in the soil, leading to their demise. Additionally, Ovavesicula popilliae, a microsporidian fungus, infects the larvae’s internal tubules, impairing their reproduction and winter survival. Many of these methods are employed in government efforts to control and reduce Japanese beetle populations in Colorado and nearby regions.
9. Rotate Plantings When Possible
Japanese beetles are drawn to certain plants, including Hollyhock, Gaura, Rose of Sharon, crabapple trees, Japanese maples, Peking cotoneaster, beans, basil, raspberry bushes, grapevines, and others. By rotating the types of plants in your garden, you can disrupt their lifecycle and help minimize infestations.
10. Stay on Top of Lawn Maintenance
Consistently mow and care for your lawn to prevent Japanese beetle larvae from maturing in the soil. Applying insecticides early in the season, while the beetles are still in their larval stage, will eliminate them before they grow into adults.
11. Plant Companion Plants
Certain plants, such as garlic, chives, and catnip, can help repel Japanese beetles. Try planting these alongside more vulnerable plants to deter the pests. For more information on companion planting, check out our blog, "What Is Companion Gardening?".
12. Encourage the Presence of Natural Predators
Encourage natural predators like birds, toads, spiders, assassin bugs, predatory stink bugs, and other beneficial insects to visit your garden. These creatures can help keep Japanese beetle populations in check. Create habitats that attract and support these helpful insects and animals.
Japanese Beetle: What They Are & How to Get Rid of Them
Japanese beetles can be challenging to manage, and no single method guarantees complete eradication. Combining multiple strategies often yields the best results. When using chemical pesticides, exercise caution, as they can harm beneficial insects and disrupt your garden's ecosystem. Always follow product label instructions and consider eco-friendly alternatives when possible. If you need assistance with pest identification or management, we're here to help! Explore our blog for more information on common pests and diseases, shop for pest control products in our online store, or visit the Garden Center for professional advice.