The only way to get rid of the adults is to trap them and kill or spray. Now, at this time, put down Milky Spore( a powder form)around all plants. This goes into the ground and the bacteria destroys the developing grubs of the Japanese Beetle. Next spring you will only have a few. It needs to be repeated every 3-4 yrs. It also destroys iris borer grubs as well as other grubs. I've used for 10 years.