Japanese Beetle

Identifying the insect

Japanese beetles have 4 life stages: eggs, larvae, pupae, and adults.

1. Eggs: Japanese beetles lay small eggs about 8-10 centimetres beneath the soil in an area near a preferred feeding site. These eggs can appear white, creamy, or even translucent in colour and are originally elliptical in shape but become larger and more spherical as they mature.
   
   
2. Larvae: Larvae are about 2.5 centimetres in length with a creamy white body and yellowish-brown head. They’re typically folded in a c-shape and can be distinguished from other species of larvae based on their V-shaped spines.
   
   
3. Pupae: Japanese beetle pupae look similar to adults, but have their legs, antennae, and wings tucked closely to their abdomen. Pupae are creamy or tan in colour but turn metallic green as they mature.
   
   
4. Adults: Adults are about 1 centimetre in length and appear oval from above. Their abdomens, thorax, and heads are metallic green, and their wing coverings are copper-brown. Japanese beetles have 5 distinctive bright white tufts of hair along each side of the abdomen. Adults tend to congregate together in large groups when feeding and are rarely seen alone.

Identifying damage caused by insect

Adult Japanese beetles feed on the foliage and fruits of over 300 plant species, several of which are found in gardens and fields. These beetles skeletonize the foliage by feeding between the veins of the leaf, creating a lace-like pattern.

Larvae growing underground will feed on the roots of lawn grasses and garden plants, creating patches of dead or dying material.

When they’re ready to lay eggs (usually around August), adult females will burrow into the soil and lay up to 5 eggs at a time before leaving to feed, mate, and lay more eggs elsewhere. Each female lays about 60 eggs over the course of her 30–45-day life.

After 1-2 weeks in the soil, eggs will hatch into larvae and begin feeding on the roots of grasses and plants. The larvae remain feeding underground through the fall and eventually dig deeper in the ground to hibernate in response to cold winter temperatures. At the onset of spring and warmer temperatures, larvae will begin feeding close to the surface again to continue development. Mature larvae will pupate around June and emerge as adults in June and July. Adults are very active in July and August, especially on clear warm summer days. Japanese beetles only undergo one generation per year, meaning adults die shortly after mating and egg laying. 

These beetles are found in a variety of habitats, including gardens, grasslands, forests, and urban spaces.

Japanese beetles tend to gather and feed on plant material growing directly in the sun, beginning at the top of the plant and moving downward. They feed on many different ornamental and agricultural plants, such as elm, maple, black walnut, fruit trees (e.g., cherry, plum, apple, apricot, peach, etc.), soybean, asparagus, corn, tomato, blueberries, blackberries, and grapes.

In the United States, Japanese beetles have spread primarily through States east of the Mississippi River, though partial infestations have been found in neighbouring States such as North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas. Quarantines have been established to protect habitats in the western States, such as Arizona, California, Nevada, Oregon, Washington, and Utah.

Japanese beetles were first found in Canada in 1939 in a tourist’s car arriving in Nova Scotia from Maine by ferry. Since then, they have spread through a few Canadian provinces, including Nova Scotia, Prince Edward Island, Quebec, and Ontario. While not shown in the map below, Japanese beetles have also been found in British Columbia. 

Ecological

Japanese beetles reduce available food for wildlife during larval and adult feeding. Feeding damage can also stress plants and reduce growth, making them more susceptible to attacks by other insects or disease.

Economic

According to the United States Department of Agriculture, Japanese beetles are one of the most significant turf-grass pests that cost an estimated $460 million per year to control.

Japanese beetles also feed heavily in pastures and crop fields, destroying plants and reducing yields. A risk assessment was conducted by the British Columbia Ministry of Agriculture to assess the impact of Japanese beetles if they were to establish and spread in the province. The report estimated potential annual crop damage to be $14.5 million under these scenarios, though the province has been successful in preventing the spread so far.

An economic survey of the British Columbia golf industry estimated upwards of $13.6 million in annual turf grass damage, with additional costs associated with sod production.  

Social

Underground larvae feeding on the roots of grasses and plants can damage lawns, golf courses, sports fields, and parks, impacting recreation and aesthetics. The presence of larvae can also attract animals, such as birds and mammals, that dig at the brown patches of grass in search of food.

Monitor the health of plants and crops regularly for any signs or symptoms of Japanese beetle. Catching this pest early before they start feeding in large numbers is important, since damaged plants release compounds that attract more beetles. Finding and removing beetle infestations early can protect plants and mitigate their impacts.

Mechanical Control

Removing individual beetles by hand can be an effective option if population numbers are low on small plantings. Shaking the branches of infested plants can dislodge beetles easily, especially when done early in the morning when the beetles are still cool and sluggish. Japanese beetles will die when put into a container of soapy water.

The use of Japanese beetle traps is generally not recommended to control populations. Studies have shown that these traps actually lure more beetles to the area, attracting more adult beetles than they catch. In some cases, these traps have led to increased foliar damage on host plants.

Try to prevent Japanese beetle infestations on high value plants by covering them with cheesecloth or other fine netting materials.

Biological Control

Pathogenic nematode products are available and can be applied late summer or early fall to control foliar feeding the following season. These products can prevent larvae from emerging in a field where it was applied, but it won’t impact larval emergence in neighbouring areas that have not been treated. This means foliage damage may still occur the following year if populations have not also been managed elsewhere.

Chemical Control

Products containing imidacloprid or chlorantraniliprole can be used as larvicides to control underground larvae and damage to lawns. Larvicides such as Acelepryn (with active ingredient chlorantraniliprole) target root eating larvae and are not harmful to people or wildlife. Ground applications are applied once per year by trained and licensed applicators.

Cultural Control

Quarantines and regulatory controls are sometimes put in place to prevent the spread of invasive species. For example, the government of Canada established regulatory areas in the Cities of Burnaby, Coquitlam, Port Coquitlam, and Vancouver in the province of British Columbia in 2023. The Canadian Food Inspection Agency also regulates the movement of articles that can carry Japanese beetles to prevent its spread into new un-infested areas. To learn more about the Regulations and Phytosanitary requirements in Canada, click the link below:

D-96-15: Phytosanitary Requirements to Prevent the Spread of Japanese beetle (Popillia japonica) in Canada and the United States