Japanese Beetle Combat

A dust called Sevin-5 can be sprinkled on plants. It works.

From the internet:

"Sevin® is suitable for virtually any outdoor insect problem. Use Sevin on vegetables, fruits, ornamentals, trees, shrubs, and lawns (granules and dust products only). It doesn't penetrate plant tissue and it is easily broken down by the environment. Sevin has been widely tested. With over 1,000 toxicology studies conducted to date, you are assured of a proven product. Professionals have trusted Sevin for more than 30 years. And you should too."