Several people have reported the adults eating the leaves of their grapes vines and other home landscape ornamentals. Japanese adult beetle will feed on a wide range of ornamental plants. They skeletonize foliage giving it the characteristic lacy look
Adult beetles can fly. This mobility makes it harder to control them. There are several insecticides registered for the adults. Treatments may need to be repeated to ensure adequate coverage of the plants' foliage.
Japanese beetle traps are one way to eliminate the adults. Rittenhouse says their trap is to attact male beetles, but they suggest not using the trap if you don't have a problem. This trap uses sex pheromones to attract the male beetle.
Upper Canada and Natural Insect Control have a trap that uses a floral attractant as well as a pheromone that lures both sexes.
Also nematodes are a consideration to control white grubs.