You can also buy Milky Spore disease as a powder sold in garden stores. It is a disease that only affects grubs in the soil, Japanese beetles and related ones. It is harmless to everything else. It only works on them when the soil is warm, so best time to apply it is late summer or early fall, when there are lots of grubs in the soil and the soil is warm. It works well in conjunction with the beneficial nematodes G.Cook mentioned.
It will take care of the grubs in your soil. That doesn't mean that you won't have Japanese beetles the next year, since they are good flyers. But if you apply the Milky Spore in fall and then again in spring (just to be sure it is well established), you shouldn't have to do it again, since the disease naturally multiplies through the soil.