The beetle species Popillia japonica is commonly known as the Japanese beetle. It is about 15 millimetres (0.6 in) long and 10 millimetres (0.4 in) wide, with iridescent copper-colored elytra and green thorax and head. It is not very destructive in Japan, where it is controlled by natural predators, but in America it is a serious pest of about 200 species of plants, including rose bushes, grapes, hops, canna, crape myrtles, and others.

It is a clumsy flier, dropping several centimeters when it hits a wall. Japanese beetle traps therefore consist of a pair of crossed walls with a bag underneath, and are baited with floral scent, pheromone, or both. However, studies done at the University of Kentucky suggest traps attract more beetles than they actually trap, thus causing more damage along the flight path of the beetles and in the vicinity of the trap than may have occurred if the trap were not present.

These insects damage plants by skeletonizing the foliage, that is, consuming only the leaf material between the veins.

As the name suggests, the Japanese beetle is native to Japan. The insect was first found in the United States in 1916 in a nursery near Riverton, New Jersey. It is thought the beetle larvae entered the United States in a shipment of iris bulbs prior to 1912, when inspections of commodities entering the country began. "The first Japanese beetle found in Canada was in a tourist's car at Yarmouth, arriving in Nova Scotia by ferry from Maine in 1939. During the same year, three additional adults were captured at Yarmouth and three at Lacolle in southern Quebec."

Life Cycle and Habits

The adult beetles normally emerge during the last week of June through July. The first beetles out of the ground seek out suitable food plants and begin to feed. These early arrivals begin to release an aggregation pheromone (odor) that attracts additional adults. Newly emerged females also release a sex pheromone that attracts males. After feeding and mating for a day or two, the females burrow into the soil to lay eggs at a depth of 2 to 4 inches. Females lay 1 to 5 eggs before returning to plants to feed and mate. This cycle of feeding, mating and egg laying continues until the female has laid 40 to 60 eggs. Most of the eggs are laid by mid-August though adults may be found until the first frost. The eggs hatch in 8 to 14 days and the first instar larvae dig to the soil surface to feed on roots and organic material. The first instars shed their skin (molt) in 17 to 25 days. The second instars take 18 to 45 days to mature and molt again. Most of the grubs are in the third instar by late September and by October they dig deeper into the soil to overwinter. The grubs return to the surface in the spring as the soil temperature warms, usually in mid-April. The grubs continue their development and form a pupa in an earthen cell 1 to 3 inches in the soil.

Mid-summer rainfall and adequate soil moisture are needed to keep eggs and newly-hatched grubs from drying out. Females are attracted to moist, grassy areas to lay their eggs; thus, irrigated lawns and golf courses often have high grub populations, especially during otherwise dry summers. Older grubs are relatively drought resistant and will move deeper into the soil if conditions become very dry. Japanese beetle grubs can withstand high soil moisture, so excessive rainfall or heavy watering of lawns does not bother them.

As Japanese beetle grubs chew off grass roots, they reduce the ability of grass to take up enough water to withstand the stresses of hot, dry weather. As a result, large dead patches develop in the grub-infested areas. The damaged sod is not well-anchored and can be rolled back like a carpet to expose the grubs. If the damage is allowed to develop to this stage, it may be too late to save the turf. Early recognition of the problem can prevent this destruction.

Japanese beetles overwinter in the grub stage. When the soil cools to about 60°F in the fall, the grubs begin to move deeper. Most pass the winter 2 to 6 inches below the surface, although some may go as deep as 8 to 10 inches. They become inactive when soil temperature falls to about 50°F.

When soil temperature climbs above 50°F in the spring, the grubs begin to move up into the root zone. Following a feeding period of 4-6 weeks, the grubs pupate in an earthen cell and remain there until emerging as adults

During the larval stage, the Japanese beetle lives in lawns and other grasslands, where it eats the roots of grasses. During that stage, it is susceptible to a fatal disease called milky spore disease, caused by a bacterium called milky spore, Paenibacillus (formerly Bacillus) popilliae. The USDA developed this biological control and it is commercially available in powder form for application to lawn areas. Standard applications (low density across a broad area) take from one to five years to establish maximal protection against larval survival (depending on climate), expanding through the soil through repeated rounds of infection, in-vers can be used to exclude the beetles; however, this may necessitate hand pollination of flowers. Kaolin sprays can also be used as barriers.

Research performed by many US extension service branches has shown pheromone traps attract more beetles than they catch. Traps are most effective when spread out over an entire community, and downwind and at the borders (i.e., as far away as possible, particularly upwind), of managed property containing plants being protected. Natural repellents include catnip, chives, garlic, and tansy, as well as the remains of dead beetles, but these methods have limited effectiveness. Additionally, when present in small numbers, the beetles may be manually controlled using a soap-water spray mixture, shaking a plant in the morning hours and disposing of the fallen beetles, or simply picking them off attractions such as rose flowers, since the presence of beetles attracts more beetles to that plant.

Adult Control

By noticing when the first adults arrive on a property, you can pick off and destroy these scouts that attract additional pests. The adults are less active in the early morning or late evening. They can be destroyed by dropping into a container of soapy water.

The adults do not like to feed on ageratum, arborvitae, ash, baby's breath, garden balsam, begonia, bleeding heart, boxwood, buttercups, caladium, carnations, Chinese lantern plant, cockscomb, columbine, coralbells, coralberry, coreopsis, cornflower, daisies, dogwood (flowering), dusty-miller, euonymus, false cypresses, firs, forget-me-not, forsythia, foxglove, hemlock, hollies, hydrangeas, junipers, kale (ornamental), lilacs, lilies, magnolias, maple (red or silver only), mulberry, nasturtium, oaks (red and white only), pines, poppies, snapdragon, snowberry, speedwell, sweet pea, sweet-William, tuliptree, violets and pansy, or yews (taxus).

Several traps using a floral lure and sex attractant are available. These traps are not recommended for general use unless special conditions can be met. The traps have been demonstrated to be effective in reducing damage and populations only when landscapes are isolated from other Japanese beetle breeding areas or when mass trapping (everyone in the neighborhood) is used. In most urban areas, traps tend to attract more beetles into the area than would normally be present. In this situation, adult feeding and resultant grub populations are not reduced.

The adults can be controlled by spraying susceptible plants with insecticides. Over-the-counter pesticides available for this include: acephate (Orthene), carbaryl (Sevin), and several pyrethroids - bifenthrin, cyfluthrin, deltamethrin, lambda-cyhalothrin, permethrin, and others. Applications of imidacloprid (=Bayer Advanced Tree & Shrub Concentrate) generally need to be made 20 days before anticipated Japanese beetle adult activity. During the heavy adult activity periods, sprays may be needed every 5 to 10 days.

Grub Control

The bacterial milky diseases, Bacillus popilliae Dutky, has been quite effective at controlling the grubs in certain areas of the eastern United States. The spore count must build up for 2 to 3 years to be very effective and during this time you should not use an insecticide against the grubs that are needed to complete the bacterium cycle. In Ohio and Kentucky, test trials have not produced satisfactory results. Additional experiments are needed to determine the lack of efficacy of milky disease in these soils.

Insect parasitic nematodes have recently become commercially available. Products that contain strains of Steinernema carpocapsae (Biosafe, Biovector, Exhibit, Scanmask) have been marginally effective against white grubs in turf. Preparations containing Heterorhabditis spp. seem to be more effective. Apply the nematodes when the white grubs are small. Irrigate before and after applying the nematodes.

The grubs are best controlled when they are small and actively feeding near the soil surface, usually late July to mid-August. However, with the development of new grub control chemistry (e.g., imidacloprid [Merit] and halofenozide [MACH2]), applications in June and July have sufficient residual activity to kill the new grub populations as they come to the soil surface in late July through August. Control of grubs in late-fall or early-spring is difficult, at best, because the grubs are large and may not be feeding. Only trichlorfon (Dylox) and carbaryl (Sevin) formulations are available for such rescue treatments. The key to good control is to make an even application and water thoroughly.

Japanese Beetle Management for Minnesota
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Japanese beetles feed on a large range of hosts, including leaves of plants of the following common crops:
Beans, strawberries, tomatoes, peppers, grapes, hops, roses, cherries, plums, pears, peaches, raspberries, blackberries, corn, peas, blueberries, and these genera:

• Hemerocallis
• Heuchera
• Hibiscus
• Humulus
• Hydrangea
• Ilex
• Impatiens
• Ipomoea (morning glory)
• Iris
• Lagerstroemia
• Liatris
• Ligustrum
• Malus (apple)
• Malva
• Myrica
• Ocimum (basil)
• Oenothera
• Parthenocissus
• Phaseolus
• Phlox
• Physocarpus
• Pistacia
• Platanus
• Polygonum
• Populus
• Prunus

• Quercus
• Ribes (gooseberry, currants, etc.)
• Rheum
• Rhododendron
• Rosa
• Rubus (raspberry, blackberry, etc.)
• Salix (willows)
• Sambucus
• Sassafras
• Solanum
• Syringa
• Thuja (arborvitae)
• Tilia (linden, lime, or basswood trees)
• Toxicodendron
• Ulmus
• Vaccinium
• Viburnum
• Vitis
• Weigelia
• Wisteria
• Zea
• Zinnia

Plant Selection

Careful selection of plant species when replacing or adding to your landscape is the key to avoiding annual battles with Japanese beetles. Some species and cultivars are highly preferred by the adults and should be avoided where the beetle is abundant. Plants that are especially prone to damage include roses, grapes, lindens, sassafras, Norway maple, Japanese maple, purple-leaf plum, and others (Table 1). Many varieties of flowering crabapples are also severely attacked by the beetles, although some cultivars are resistant.

Fortunately, many common trees and shrubs are much less attractive to Japanese beetles (Table 2). These differences in susceptibility should be considered when selecting plant species and cultivars for use in Japanese beetle-infested areas.

Sue Writes,

Can the Beetle Bagger Japanese Beetle Trap be used in the house, specifically the kitchen?