Japanese beetle, Popillia japonica Newman, is an introduced pest that has been in the United States since 1916 and in Tennessee since 1936. The larvae, a type of white grub, feed on the roots of grasses and a variety of crops and ornamental plants. Grubs molt twice by the fall and overwinter in the third instar stage. They reach full maturity in the spring and pupate in an earthen cell in the soil.

Adult beetles emerge from late May through June. The adult beetle is a broadly oval insect nearly one-half inch long. The body is a bright metallic green with legs a darker shade of green. The wing covers are a coppery brown. The gregarious adult beetles aggregate on host plants to feed and mate for the next 30-60 days. Japanese beetle adults feed on more than 300 varieties of plants. Certain preferred host plants such as American linden, Japanese maple, crabapple, crapemyrtle, plum and cherry tend to suffer much more feeding damage than the less-preferred host plants, such as magnolia, redbud, dogwood, red maple, silver maple, tuliptree, sweetgum, ash, boxwood, black oak, white oak, and northern red oak.

Adult beetles skeletonize leaves. Severe feeding causes the leaves to turn brown and often drop. Feeding damage on thin, fine-veined leaves or flower petals will often appear as large, irregularly shaped cut-outs. Refer to “The Japanese Beetle and Its Control,” PB 946, for additional information.

Japanese beetle traps are not recommended, even though large numbers of adult beetles can be caught in the traps. Trapping alone will control only a small percentage of the beetles and will attract more Japanese beetles to the area! Once in the area, they feed on susceptible plants and cause more damage than if a trap had not been used.

Japanese beetles can be removed by hand-picking the beetles off and placing them into a shallow dish of soapy water.

Protective insecticide sprays can be made to the foliage of susceptible plants during the period when Japanese beetle adults are active. Several sprays on a 7-10 day schedule may be necessary to prevent excessive feeding damage.

For chemical control recommendations, consult the Insect and Plant Disease Control Manual, UT Extension Publication 1690, found here. Please contact your local Extension office for specific pesticide recommendations.