Japanese Beetles

The Japanese beetle (Popillia japonica Newman) is a highly destructive plant pest native to Japan as the name suggests. It is not considered a serious pest in Japan where its natural predators keep populations in check. However it is rampant in the United States where infestations are regularly reported. Strict regulations and pest management strategies have prevented the establishment of the Japanese beetle in other parts of the country.

The adult Japanese beetle is approximately ½ an inch long, it has an iridescent metallic green body and copper colored outer wings. Japanese beetles are harmful pests in the larval and adult stages. Adults feed on the foliage and fruits of several hundred species of plants and are a serious threat to American agriculture. The adults consume the leaf material between the veins and leaving large holes in leaves The grubs or larva develop in the soil and feed on the roots of various plants and grasses causing damage to turf on lawns, parks and golf courses.

There is no quick way of getting rid of the Japanese beetle once it is established. However there are chemical, biological and cultural methods that can be employed to manage these pests. The concept of integrated pest management has proven to be a useful, efficient and environmentally sound method of pest control. This method aims to manage pests and not eradicate them as it is realized that control methods may also harm potentially beneficial organisms in the environment. In addition eliminating the pest can cause disruptions in the food web of an ecosystem and can damage the ecosystem.

To control the Japanese beetle a rough estimate of the beetle population should be obtained. This can be done by using mechanical traps for adult beetles which attract adult beetles using a combination of pheromones and floral lures. As a result of their clumsy flying and the design of the trap the beetles are captured by the trap. If beetles fill the trap within a day or so, treatment will be necessary. A random sampling technique can be used to estimate beetle grub populations. A one square foot quadrant can be placed at random locations on the lawn and soil should be dug from these locations using a shovel. Turn the sod over a newspaper and count the number of white grubs visible. If the grub density is over 10 per square foot treatment will be required.

Chemical control methods can be used to manage Japanese beetles however the risks and benefits of the pesticide must be determined prior to using it. Correct timing and application are also essential for successful control. It is important to read and follow the directions and safety precautions when using chemicals. However the use of these chemicals is not encouraged due to the potential environmental threat they pose.

Biological control agents such as parasites, nematodes and fungi can be used to control Japanese beetle populations. Some of these control agents are commercially available and though they take longer to produce the same results as insecticides biological control agents last longer in the environment and have no adverse effect on the environment.

Cultural methods such as habitat manipulation can also be employed to suppress Japanese beetle populations. This includes planting resistant plant species and removing the more susceptible ones. Diseased and malnourished plants are susceptible to attack by beetles. Therefore plants and crops should be kept healthy. Also prematurely ripened fruit should be picked off plants as the odor tends to attract Japanese beetles. Homeowners and cultivators should have a well dispersed variety of plants that favors beetle resistant plant species in order to reduce the level of damage.

It is important to note that these methods do not completely eliminate the Japanese beetle but will keep populations under control and minimize the damage they inflict. People should also be aware of the pest control methods they use and be aware with the costs and risks associated with them. Community efforts such as cooperative pest management programs can go a long way in suppressing Japanese beetle attacks.