Japanese beetles are pests in the U.S. found primarily east of the Mississippi, but are rapidly spreading westward. Adults are 3/8”-1/2” long with metallic green bodies and copper/bronze wings.
Adult beetles feed on the leaves of over 300 species of plants, including roses, crape myrtles, grapes, little leaf lindens, crabapples, purple leaf plums, and Japanese & Norway maples. The larvae, or grubs, feed on turf roots.
Beetles are often active on sunny days when the temperature is over 70º F and the relative humidity is below 60%. Chewed leaves appear lacey or skeletonized and may drop prematurely. Large numbers of beetles typically appear throughout mid and late summer. They often swarm and feed in the upper tree canopy and may create a brownish “halo” effect on small trees.
Because Japanese beetles fly long distances and feed throughout most of the summer, you may need to make multiple pesticide applications to manage them and protect new growth. Follow the directions on the product you use for how often to apply or consult an arborist. For moderate populations of beetles, a new soil-injected treatment will help manage them during the season. Pheromone traps can catch large numbers of beetles, but will not protect ornamentals from damage. Traps may help if they are used by an entire neighborhood, but they are not an effective control of individual properties.