Japanese beetles are one of the most damaging insect pests in America, and for good reason. While the larvae like to feed underground on the roots of plants (including turf), the adults will devour the foliage of just about any green plant--over 270 known varieties of plants, in fact. These shiny copper-colored beetles especially enjoy munching on the fruit and leaves of fruit trees. While they are difficult to get rid of entirely, as they simply fly in from neighboring areas, there are some effective methods of killing those you find on your trees.
Pluck them off by hand. Obviously, this is labor intensive and you probably won't be able to reach the Japanese beetles that are munching away on the highest branches. Still, getting as many as you can reach will help before you turn to other methods. Protect your hand with gloves and drop the beetles in a jar of soapy water to kill them once you pluck them off the tree.
Spray the leaves of your fruit tree with an insecticidal soap. This will kill the bugs and also make the foliage taste bitter, which will deter other Japanese beetles. Make sure you thoroughly wash any fruit that may have insecticidal soap on it before eating it.
Kill the grubs. While killing the adult Japanese beetles on your fruit trees is a good first step, you will also obviously want to kill the grubs that live in the soil and feed on the roots of plants. Get rid of any grubs in the soil or lawn with milky spore (a bacteria), which is an all-natural way of killing Japanese beetles.
Prevent the beetles from returning to your fruit trees. Plant garlic around the trees. Beetles hate the strong smell, and you can harvest the garlic in the bargain.