Get a bucket of water (a gallon milk jug cut to provide a very wide opening works great). Put a drop of dishsoap in it and fill halfway with water to make frothy. Hold under the affected plants and brush the beetles into it. They often naturally drop DOWN when touched (some fly away). Allow the water to sit for several days with the carcasses in it (kind of like a sun brewed tea). Use as you wish (but frankly removing the beetles by hand in this fashion takes care of most of the issue). Repeat daily to kill the adults - fewer adults equals fewer individuals to lay eggs for next year.