Japanese beetle traps are effective if placed in the right location. I use home made sticky yellow traps to get cucumber beetles. Nail a small board on a stake, paint it yellow, and coat with brush on insect rap coating. The larvae feed on the eggs and destroy the pest eggs. Spray containing the bacteria containing bacillus thuringiensis has long been used to control cabbage worms and other related species.
Natural insecticides made from certain plants are the heavy weights of organic pest control.
Rotenone, pyrethrin, sabadilla, and others are broad spectrum poisons and should be used sparingly. Fortunately, these insecticides break down quickly and there fore do not leave residues.