Japanese Beetle Control in Grapes

Japanese Beetle Identification

• The Japanese beetle (Popillia japonica) feasts on the foliage and fruit of about 300 species of plants, making it one of the most flagrant pests of everything from ornamentals to vegetable and fruit plants. It is especially fond of those of the grape (Vinis) species. The beetle measures less than 1 inch in length and is distinguished by a bright green metallic body that is set off by the striking color of its copper brown wings. A tuft of white hair sticks out from underneath each wing.

Damage

• A prolific skeletonizer of leaves, the Japanese beetle damages plants to the extent that large segments defoliate. Grapes can withstand some loss of foliage but will be harmed in cases of extreme infestation. Gardeners should inspect grapes at least twice weekly, looking for both the insect itself and signs of feeding. Japanese beetles forage in groups, usually starting near the top of a plant and working their way downward, leaving behind a collection of leaves full of holes.

Infestation

• Japanese beetles enjoy full sunshine and typically only infest grape vines that are planted in direct sunlight. Additionally, they are social creatures and are attracted to plants that already hold a population of their brethren. Therefore, it is important to monitor the grape and quickly remove any beetles that have inhabited the specimen. These pests are extremely mobile and able to fly several miles, quickly gathering on a plant and beyond the eye of an unwary gardener.

Control

• Picking away the Japanese beetle by hand provides a decent level of control. Search for the insect in the morning while it is sluggish and knock it into a pail of soapy water to destroy it. If infestation is extensive -- with more than 15 percent of the leaves of the grape damaged -- chemical control is likely vital. A number of insecticides control the Japanese beetle. In some instances, localized spraying on a small number of branches may suffice.