How to Get Rid of Japanese Beetles

Japanese beetles (Popillia japonica) are known for their beautiful iridescent green shells and the devastation they cause to gardens and landscapes. These pests are notorious for their summer feasts where they indulge in a six-week feeding frenzy that can decimate roses, perennials, bushes, and a variety of fruit trees. While they may prefer certain plants, when they reach larger populations, they are known to consume other plants that they would typically ignore, leaving a trail of destruction in their wake. The key to managing these voracious eaters lies in early detection and intervention. As we dive into strategies to mitigate the impact of Japanese beetles, we'll explore comprehensive methods to prevent them from turning your garden into their dinner plate to ensure your plants remain vibrant and thriving throughout the season.

What Are Japanese Beetles?

The Japanese beetle is an unwelcome invasive species that originated from Japan. Since its introduction onto American soil in 1916, it has established itself as a notorious pest across much of the United States, particularly east of the Mississippi River. These beetles are about 3/8 inches long and are easily recognizable by their coppery green coloring. Unlike many pests that have a preference for a specific type of plant, Japanese beetles are voracious leaf eaters that do not discriminate. This makes them a threat to a vast array of plant species. Among their favorites are roses, yet their appetite extends to hundreds of different species which makes them a significant pest to both ornamental plants and crops.



The accidental introduction of the Japanese beetle to the United States marked a significant ecological shift. They were originally confined to Japan where they were kept in check by natural predators. However, the beetles managed to get brought over accidentally in freight that was shipped to the east coast. Here they found a favorable environment in the U.S. that was devoid of any form of natural predator. Despite attempts to prevent their spread through legislation like the 1912 law prohibiting the import of plants rooted in soil, the beetles managed to establish a strong foothold that has remained since their original introduction. By 1920, efforts to eradicate the beetle were abandoned due to its prolific and widespread nature.

What Kind of Damage Do Japanese Beetles Cause?

Japanese beetles, both in their larval and adult stages, unleash a two-pronged attack on landscapes and crops which cause significant damage that can devastate gardens, lawns, and agricultural areas. As adults, these beetles are aggressive, indiscriminate feeders that consume the foliage and flowers of over 300 varieties of ornamental and agricultural plants. Japanese beetle damage is not subtle, and they leave a trail of destruction that is easy to spot but difficult to mitigate. The adult beetles' method of feeding results in leaves and flowers being left skeletonized. This means they chew the leaf tissue away from the veins and create a lace-like appearance that is unmistakable and often the first sign of an infestation.



Adult beetles aren’t the only problem. The larval form poses a significant problem to lawns as well. Grubs feed on the root systems of grass, causing unsightly, unhealthy brown patches across lawns. These areas of damaged grass can be easily pulled up due to the weakened roots, which is a clear indication of the underground destruction wrought by these pests. Whether they are undermining the health of lawns as grubs or decimating plants as adults, Japanese beetles are a problematic and destructive pest for any gardener or farmer.

How Can You Get Rid of Japanese Beetles?

Tackling a Japanese beetle infestation requires a two-fold strategy aimed at both the voracious adults and the destructive larvae. Getting rid of adult Japanese beetles is crucial to prevent further damage to foliage and flowers because these beetles can rapidly decimate a wide range of ornamental and agricultural plants. Methods such as hand-picking, using beetle traps, and using targeted pesticide treatments are effective in managing adult populations. However, to ensure a comprehensive approach, addressing the root of the problem—literally—by targeting the larvae is equally important. Larvae, or grubs, residing in the soil feed on grass roots which leads to significant lawn damage. Strategies to eliminate these grubs include soil aeration, the application of beneficial nematodes or soil bacteria, and the introduction of natural predators or milky spore disease. By combining efforts to combat both life stages of the Japanese beetle, gardeners and homeowners can significantly reduce the impact of these pests on their landscapes and crops.

Getting Rid of Adult Japanese Beetles

Combatting adult Japanese beetles effectively requires adopting specific strategies to reduce their population and minimize the damage they inflict on a wide array of plants. The following are all ways to get rid of adult Japanese beetles that can be used together to formulate a much more comprehensive integrated pest management strategy.

Hand Pick the Beetles Before Drowning Them

Hand-picking Japanese beetles is a direct, eco-friendly approach that can significantly reduce their numbers in your garden. This method involves knocking the beetles off plants directly into a bucket of soapy water. Wearing nitrile gloves can make this task less unpleasant for many gardeners. Entomologists and seasoned gardeners alike note that while you can hand pick at any time of day to mitigate feeding damage, early evening yields the most success. The best time to undertake this task is in the early evening, around 7 p.m., when beetles are most active yet somewhat sluggish as this makes it easier to collect them.

Start by preparing a bucket with water and a small amount of dish detergent. The soap breaks the water's surface tension which ensures that the beetles cannot escape once they fall in. You can either gently shake the plants or tap them to dislodge the beetles directly into the bucket. Be quick and deliberate in your movements because Japanese beetles are quick to sense disturbance and may fly away. Although this may be time-consuming, this method can drastically reduce the beetle population in your garden if done repeatedly.

Use a Japanese Beetle Trap

The use of Japanese beetle traps is a topic of considerable debate among gardeners and experts due to their potential to attract more beetles than they actually capture. While these traps can indeed lure beetles away from plants, their effectiveness is limited as they typically capture only about 75% of the beetles they attract, leaving the remaining 25% free to feast on your garden. Despite this, traps can still play a role in managing beetle populations if used correctly. To optimize their effectiveness, it's advised to set traps early in the season, which helps catch beetles before they have a chance to reproduce. Positioning the trap at least 50 feet away from any plants you wish to protect is crucial to avoid drawing beetles directly to the areas you're trying to safeguard.

When using beetle traps, regular maintenance is key. Traps should be emptied daily because dead beetles piling up can deter others from entering the trap which can reduce its effectiveness. It is important to note that traps are not a comprehensive solution on their own. However, when integrated with other Japanese beetle control measures, they can contribute to a multi-pronged defense against these invasive beetles.

Apply Targeted Pesticides

When tackling Japanese beetle infestations, applying targeted pesticides can be an effective strategy. One of the most recommended options is Neem oil which is an organic insecticide and fungicide that has proven effective against adult Japanese beetles. Neem oil works by interfering with the beetle's life cycle. When the active chemical in Neem oil is ingested by the beetles and subsequently passed onto their eggs, it leads to the premature death of the larvae before they can mature. This makes Neem oil a pivotal tool in preventing the proliferation of these pests. However, it is crucial to apply Neem oil before beetle populations become too large, as its effectiveness diminishes with higher beetle population density. Additionally, while Neem oil is generally low risk to bees and other beneficial insects, it should be used cautiously near water sources due to its toxicity to aquatic life.



Gardeners should be wary of the type of pesticides they use. Systemic pesticides, which are pesticides that are absorbed by plants from the soil, have broader ecological consequences. The active ingredients in many systemic products have been linked to honeybee colony collapse disorder. Therefore, while these pesticides might offer a convenient solution for eliminating pests, their long-term impacts on pollinator populations and overall ecosystem health make them a less favorable option. 

Getting Rid of Japanese Beetle Larvae

Controlling Japanese beetle populations effectively requires addressing not just the adult beetles but also their larvae, which develop in the soil and can cause extensive damage to lawns and gardens. Targeting these larvae is crucial for breaking the life cycle of the beetles and preventing future infestations. Various methods can be employed to combat larvae, including aerating the soil to disrupt their habitat, applying nematodes that naturally parasitize beetle larvae, using beneficial soil bacteria to inhibit larval development, introducing predators that feed on the larvae, and employing milky spores, a biological control that specifically targets Japanese beetle larvae. Each of these strategies offers a sustainable approach to managing beetle populations by focusing on the underlying cause of infestation.



Use Aerators to Penetrate the Soil

One innovative and straightforward method to disrupt the lifecycle of these grubs is by using soil aeration techniques during key times of their development. In early fall, grubs are actively feeding on grass roots near the surface of the soil which makes them particularly susceptible to mechanical interventions. Although lawn aerating sandals are often touted for their ability to help aerate lawns, entomologists have found that the spikes on these sandals are ideally suited for a different purpose: penetrating the soil and spearing the grubs. This method is particularly effective in areas of the lawn that show signs of browning, where grub activity is likely high. Additionally, a similar approach can be applied in early spring when soil temperatures reach around 60 degrees Fahrenheit. Checking average soil temperatures online can help determine the optimal timing for this treatment. This mechanical control method is not only simple but also one of the few that proves effective against the grubs that eventually mature into adult Japanese beetles.

Spray Nematodes

Using soil-dwelling nematodes, which are akin to microscopic worms, offers a highly effective biological approach to controlling Japanese beetle larvae in your garden or lawn. These nematodes are natural predators that seek out and kill grubs by invading their bodies and releasing bacteria that is lethal to the larvae. Among the various types of nematodes, Heterorhabditis bacteriophora is particularly effective against Japanese beetle grubs. To ensure the quality and viability of these beneficial organisms, it is essential to purchase them from reputable suppliers that specialize in beneficial insects. For optimal results, nematodes should be applied to the soil either in early fall or spring as these times align with the life cycle stages of the grubs when they are most vulnerable. It is important to note that nematodes do not persist in the soil, so they require annual applications to maintain control over the beetle population. This method not only targets the larvae effectively but also enriches the biological diversity of your garden's ecosystem.

Use Beneficial Soil Bacteria

Another innovative and environmentally friendly approach to combating Japanese beetle larvae involves the use of Bacillus thuringiensis galleriae (BTG). This naturally occurring soil bacterium specifically targets the grubs of Japanese beetles at a crucial stage in their lifecycle. BTG operates by producing spores that are toxic only to the larvae. The larvae ingest these spores while feeding on roots in the soil. This method stands out because it matches the efficacy of chemical pesticides in killing grubs, yet it is completely safe for beneficial insects including bees and other pollinators. It also poses no risk to humans, pets, or other wildlife and it does not harm plants. The effectiveness of BTG lasts several weeks which makes it an ideal solution during the periods when grubs are actively feeding and most vulnerable.

Introduce Welcome Predators

Introducing natural predators to your garden is an eco-friendly strategy to manage both Japanese beetle adults and their larvae effectively. Attracting birds is one of the simplest and most effective ways to enhance biological control. Birds such as catbirds, cardinals, and robins are known to consume adult beetles, while others like starlings and crows primarily target the grubs. To encourage these beneficial birds to visit your garden, it helps to provide food, shelter, and water. As autumn arrives, flocks of starlings can often be seen actively foraging through lawns, digging up and feeding on beetle grubs which significantly reduces their numbers naturally.

Another ally in the battle against Japanese beetles is the tachinid fly, a native predator that becomes more prevalent as beetle populations increase. These flies lay eggs on the heads of adult beetles. Upon hatching, the larvae burrow into the beetle, ultimately killing it. Adult tachinid flies, meanwhile, feed on nectar and are particularly attracted to certain types of flowering plants like dill, fennel, sweet clover, gomphrena, and mint. Planting these flowers not only adds beauty and variety to your garden but also supports the lifecycle of tachinid flies. This approach not only helps in reducing the beetle population but also fosters a biodiverse and resilient garden ecosystem.

Introduce Milky Spores

Milky spore is a naturally occurring fungal disease that specifically targets the grub stage of Japanese beetles which makes this treatment option a safe alternative to chemical pesticides. Once applied to the soil, the spores infect the grubs as they feed. The infected grubs then distribute the spore further into the soil, enhancing the effectiveness of the treatment over time. This method is not only organic but also poses no risk to children, pets, and non-target species which makes it an ideal choice for gardeners seeking a sustainable pest control solution.

The best time to apply milky spore is during late summer or early fall, typically between late August and September, when soil temperatures range from 60 to 70 degrees Fahrenheit. This timing coincides with the period when Japanese beetle grubs are most active and close to the surface to maximize the impact of the treatment. Application is straightforward and guided by the directions on the product packaging:

• Spread the spore evenly across the affected areas
• Water it in to help the spores penetrate the soil and reach the grubs

Since milky spore specifically targets Japanese beetles, it has no adverse effects on beneficial insects like bees.

How to Prevent Japanese Beetles

Preventing Japanese beetles from infesting your garden and damaging your plants before they become a problem requires proactive measures and strategic planning. Employing a combination of homemade repellent sprays, physical barriers, and careful lawn management can significantly reduce the likelihood of beetle invasions. Together, these preventative strategies form a comprehensive defense against Japanese beetles that will safeguard your garden's health and vitality without relying on harsh chemicals.

Make a Japanese Beetle Repellent Spray

Creating a homemade Japanese beetle repellent spray can be an effective way to protect your plants from these voracious pests. Interestingly, one natural repellent that has shown promise utilizes the smell of dead Japanese beetles. It appears that the scent of their deceased counterparts acts as a deterrent and discourages other beetles from approaching. To make this repellent, start by collecting the bodies of beetles, either through hand-picking or from traps. These collected beetles can then be placed in a blender with a small amount of water and liquefied to form a concentrated mixture. After adding more water to dilute the mixture, strain out the solid beetle parts to obtain a clear solution. This beetle-based repellent can be sprayed directly onto plants to create an olfactory barrier that repels new beetles. Due to its natural composition, it is safe to reapply this repellent as often as needed to maintain its effectiveness throughout the beetle season. This method, while somewhat unconventional and not for the squeamish, offers a chemical-free alternative to traditional insecticides and taps into the natural aversions of the beetles themselves.

Protect Plants with Row Covers

Using row covers is an effective method to shield your plants from Japanese beetles, particularly during their peak feeding periods. Row covers, which are lightweight fabrics designed to drape over plants, create a physical barrier that prevents beetles from accessing and damaging the foliage. In the northern regions, this critical period typically spans from mid-to-late June. In the south, it begins a bit earlier, from mid-to-late May. During these 6- to 8-week feeding windows, row covers can significantly reduce the impact of these pests on your garden.



However, while row covers are excellent for keeping out unwanted insects, they also block access to pollinators, which is essential for the fertilization of many crops. Therefore, it's important to strategically manage the use of these covers, especially for flowering plants that require pollination. For example, do not cover flowering fruits and other bloom-dependent plants until after pollination has occurred and the plant has begun to set fruit. After this stage, you can safely apply the netting to protect the developing fruits from beetle damage. This careful timing ensures that your plants receive the necessary pollination while still benefiting from the protective barrier against Japanese beetles.

Don’t Water the Lawn

Managing watering practices for your lawn can significantly impact the prevalence of Japanese beetles. These beetles are drawn to well-irrigated turf because their eggs require consistent moisture to develop properly. By reducing or completely halting watering during the beetle's peak season, which typically spans from late June to late July, you can decrease the attractiveness of your lawn for egg-laying females. Letting the grass go dormant during this period is a natural way to deter beetle infestation without the use of chemicals. This method not only saves water but also makes the environment less hospitable to the larvae that would otherwise thrive under moister conditions.

Careful Planting Considerations

Thoughtful landscaping can also enhance preventative measures. Research indicates that the Japanese beetles are particularly attracted to certain plants due to their natural sugar content and specific aromatic substances. For instance, plants with higher levels of the reducing sugar dextrose, such as Japanese and Norway maples, birches, crabapples, cherries, raspberries, roses, plums, and grapes are more susceptible to beetle attacks. Avoid planting these in close proximity or creating clusters of these susceptible species as they can become hotspots for beetle activity. By strategically planning your garden's layout and choosing less attractive plant varieties, you can further discourage Japanese beetles from settling in your outdoor spaces.

Contact EcoGuard if You Are Dealing with Japanese Beetles

If you're facing a challenging battle against Japanese beetles and need expert assistance, don't hesitate to contact EcoGuard Pest Management. Our team of knowledgeable professionals is equipped with the tools and expertise necessary to effectively manage beetle infestations and protect your garden and lawn. Whether it's implementing targeted treatments or offering advice on preventive measures, EcoGuard is here to help ensure your outdoor spaces remain beautiful and free from pests. Reach out today to learn more about our services and how we can assist you in safeguarding your property from the destructive impact of Japanese beetles.

Getting Rid of Japanese Beetle FAQs