The eastern U.S. is home to the destructive Japanese beetle, which was accidentally introduced in the early 20th century. This insect occurs as far south as Alabama and Georgia and is responsible for "skeletonizing" the leaves of 300 types of plants. The beetles also eat flowers and fruit during their June and July feeding frenzy. The Japanese beetle is green with coppery wings and grows to 7/16 inch. If you avoid planting roses, grapes, maples, plums and crabapples, you'll be providing the beetle less food. This pest rarely eats or damages some other plants, such as persimmons, ash, holly, oaks and others.
Handpick Japanese beetles when you first notice them on your tree or trees. In the early morning, this insect is sleepy and sluggish--you can shake the tree and catch the beetles in a bucket of soapy water. Pick up any insects that miss the bucket and place them into it.
Cover your susceptible tree or trees with cheesecloth or floating row cover, sold as Reemay, before the beginning of Japanese beetle season in June. This method is most practical when your trees are small because larger trees can be difficult to cover.
Control the Japanese beetle from the ground up by eliminating its larvae, or grubs, which live underground. If you know your area and your trees are prone to Japanese beetle attacks in the summer, you can prevent a large infestation by sprinkling a product called milky spore on the ground in areas near your trees. The grubs eat grass roots, so concentrate on grassy areas near your trees. Sprinkle 1 tbsp. of milky spore every 4 feet and repeat the treatment two or three times in spring, until mid to late June when the grubs pupate and turn into beetles.
Apply an approved chemical pesticide to your trees when you have a large infestation of Japanese beetles. Effective products include cyfluthrin, bifenthrin, carbaryl, deltamethrin and permethrin. These insecticides kill and keep away beetles for two to three weeks; after that time, you must reapply insecticide to control new beetles that flock to your tree.
Use a product with neem if you prefer not to use a poison. However, natural remedies such as neem keep the insects away for only a few days, so you must spray your tree more frequently than you would if you're using a chemical product.
Trap beetles with special traps designed for this insect. However, the baits used in such traps can attract beetles that might not find your tree if the traps and their attractive bait were not present. Keep these traps at the borders of your property if you decide to use them.