I was in the garden this morning and saw my first Japanese Beetle of the season. The Neem oil we have been using on the cucumber beetles is effective on the Japanese beetles, too.
You can hand-pick them or hold a pail of soapy water under the plant and give it a little shake. This causes the beetles to drop into the soapy water and drown. Either way, if you see them . . . act. It doesn’t take long for Japanese beetles to skeletonize a plant leaf.