Unfortunately, the most effective way of getting rid of Japanese beetles is to hand pick them. It's time consuming, but it works, especially if you are diligent.
Last week Janaya and Keauna visited. They devised a clever method of ridding my garden of these beetles -- and they were very diligent. Within a short amount of time the girls had a plastic water bottle filled with these nasty pests. Janaya had a knack for finding the beetles - she was the "spotter;" Keauna was the "finisher." Keauna held her water bottle up close to the beetle/s and with the cap, just slid them into the water bottle. Done. I told the girls they could have full-time work here for the next month!
Their help was very much appreciated. Luv ya both!