The Japanese beetle (Popillia japonica) is an invasive insect species that has become a notorious agricultural and ornamental pest in many parts of the world, particularly in North America. It is native to Japan, where it is naturally controlled by predators and environmental conditions. However, after being accidentally introduced into the United States in the early 20th century—likely via imported plant material—it established rapidly and has spread across much of the eastern and midwestern regions, causing significant damage to crops, turf, and gardens.
Taxonomically, the Japanese beetle belongs to the order Coleoptera (beetles), family Scarabaeidae (scarab beetles), and subfamily Rutelinae, which includes many other leaf beetles. Its scientific name is Popillia japonica. Adult beetles are typically about 12 mm (½ inch) long, with shiny, metallic green bodies and bronze-colored elytra (wing covers). A key identification feature is the presence of six white tufts of hair on each side of the abdomen, which distinguish them from similar beetles.
In its native Japan, the beetle is just one among many garden insects and does not cause widespread harm, primarily due to native predators and pathogens that naturally limit its numbers. However, in areas where it has been introduced, particularly North America, it lacks natural enemies and has thus become a highly problematic invasive species. Other names used informally to describe the Japanese beetle include “green beetle” or “metallic beetle,” though these are not official common names and may also refer to unrelated species.
The Japanese beetle is now widespread in the eastern and central United States, parts of southern Canada, and has more recently appeared in some western states under active quarantine. It thrives in urban, suburban, and rural environments, especially where there is access to irrigated turf, ornamental plants, or agricultural crops. Preferred habitats include lawns, golf courses, gardens, pastures, and fruit orchards. Adults feed on a wide variety of plants, while the larval grubs live underground and consume grassroots, making them doubly destructive.
Natural predators of Japanese beetles include birds such as starlings, robins, and crows, as well as predatory insects like ants, ground beetles, and parasitic wasps. However, these natural enemies often do not control large populations effectively in non-native ranges. Some fungal and bacterial pathogens have also been introduced or studied as biological controls, with varying success.
Japanese beetles reproduce during the warm summer months. After mating, females burrow into the soil to lay eggs—usually in turfgrass or moist soil. These eggs hatch into white, C-shaped larvae known as grubs, which feed on grassroots and organic matter. The grubs overwinter in the soil and resume feeding in the spring before pupating into adults in early summer. Adults live for about 30–45 days, but their overlapping generations mean infestations can persist for weeks.
Diet-wise, adult Japanese beetles are highly polyphagous and feed on over 300 plant species, including roses, grapes, beans, apples, linden trees, and many other ornamentals and fruit crops. They skeletonize leaves by eating the tissue between the veins, creating a lace-like appearance. Grubs, on the other hand, feed primarily on grass roots, damaging lawns, golf courses, and pastures. This dual-stage feeding makes the Japanese beetle one of the most economically damaging pests to both homeowners and commercial agriculture in infested regions.
Habits and other facts about Japanese Beetles
Japanese beetles (Popillia japonica) are best known for their highly destructive feeding habits, both as larvae and adults. Their behavior and life cycle are tightly synchronized with warm weather, and they are most active during the summer months when they emerge in large numbers to feed, mate, and lay eggs. A single beetle may not cause extensive damage on its own, but because they often feed in swarms, they can defoliate plants rapidly and attract more beetles through pheromones and plant volatiles released by damaged vegetation.
One of their most recognizable habits is leaf skeletonization. Adult beetles feed on the tissue between the veins of leaves, leaving behind a delicate lace-like structure. They tend to prefer sunlit areas and are often seen clustering on the upper foliage of plants. Interestingly, they are also attracted to previously damaged leaves—plants that are already under attack become even more vulnerable due to the chemical signals emitted during herbivory. This behavior makes their damage both conspicuous and rapidly escalating.
Japanese beetles are also strong fliers, capable of traveling several miles in search of food and mates. During peak season, their swarming behavior can affect not just one yard or farm but entire neighborhoods. They are diurnal (active during the day), with most of their feeding and mating occurring in full sunlight, especially during mid-morning and early afternoon.
In terms of reproductive habits, females typically burrow into moist soil or turf to lay their eggs, preferring well-maintained lawns and irrigated areas. Over a single season, a female may lay 40–60 eggs in multiple batches. The resulting larvae, or grubs, are just as harmful as the adults—feeding underground on grass roots and causing widespread lawn die-off and turf damage. Their presence may go unnoticed until patches of grass begin to turn brown and lift easily from the soil like loose sod.
Another important aspect of Japanese beetle behavior is their aggregation habit. Adult beetles are attracted to the scent of damaged foliage and to the pheromones released by other beetles. This creates a positive feedback loop, where the presence of a few beetles quickly turns into a full-blown infestation. This is why early detection and control are so important for managing their impact.
A few unusual facts: Japanese beetles can survive cold winters as larvae by burrowing deeper into the soil to avoid freezing. They have also been the target of several biological control efforts, including the introduction of parasitic flies (like Istocheta aldrichi) and milky spore disease (caused by Paenibacillus popilliae), both of which target the grub stage. Despite this, they remain a persistent pest, largely due to their adaptability and the wide range of plants they can exploit.
Lastly, although Japanese beetles are not dangerous to humans—they don’t bite or sting—their impact on agriculture, horticulture, and landscaping makes them one of the most costly invasive insect species in the United States. Their habits of communal feeding, rapid reproduction, and wide host range ensure that once they’re established in an area, consistent monitoring and integrated pest management are essential.
How to get rid of japanese beetles
- Pick beetles off plants early in the morning when they’re less active. Drop them into a container of soapy water to kill them. This is labor-intensive but effective for small infestations.
- Spray neem oil directly on affected plants. When beetles ingest it, it disrupts their reproductive system. It’s especially effective on young beetles and safe for most beneficial insects when used correctly.
- Install floating row covers over susceptible plants during peak beetle activity (June to August). These act as physical barriers and are best for protecting vegetables and flowers.
- Milky spore powder (Paenibacillus popilliae) targets the grub stage of Japanese beetles. Apply it to lawns and garden beds—it multiplies over time and provides long-term control, though it takes a year or more to become fully effective.
- Microscopic roundworms like Heterorhabditis bacteriophora can be applied to soil to infect and kill beetle grubs. These biological controls are safe, natural, and work well in moist conditions.
- Commercial Japanese beetle traps often attract more beetles than they capture, worsening the problem. If used, place them far from plants you want to protect—ideally at the edges of your property.
- Avoid highly attractive plants such as roses, grapes, and linden trees if you’re in an area prone to beetles. Instead, choose less appealing species like boxwood, lilac, or forsythia.
- During beetle season, remove or cover plants that attract them the most. Reducing food sources helps break the feeding cycle and discourages aggregation.
- For severe infestations, use insecticidal soap or pyrethrin-based products labeled for Japanese beetles. These kill on contact but should be applied with care to minimize impact on pollinators.
- Since grubs thrive in moist, well-irrigated lawns, reduce watering in mid-summer when eggs are laid. A slightly drier lawn makes your turf less attractive for egg-laying females and discourages grub development.