Japanese and other beetles are fairly easy to control using organic controls and methods. First of all get rid of the pheromone traps.. Pheromone attracks beetles......... from far and wide. They sense the pheromone and come to find its source, many getting trapped and many not. The ones that are not trapped end up laying eggs in your lawn and garden and become grubs where they do a little damage to the roots. This is the important stage at which to eliminate them and the best way is very simple and easy. Distribute Beneficial Nematodes in the early spring. They will kill and destroy the grubs as they hatch and they will destroy the eggs as well.. If the nematodes do not kill all of the grubs which is unlikely, spray Neem in the early mornings. Beneficial nematodes also control many other insects as well. Fleas, ticks, wireworms, any insect that reproduces in the soil. Your local nursery should carry them. They come in 2 forms, the live form on a sponge and the dried form. I have never had good results with the dried form so stay away from it...Make sure the nematodes are fresh. There will be a date on the little package. Make sure they are less than 2 weeks old and well refridgerated. Spinosad is also an excellent organic means to kill beetles of all kinds. You can use it as a spray on the plants or use it as a drench. Mulching your garden will also reduce the number of insects that lay their eggs in the soil.
We used to have a terrible problem with them. My rosebushes would bloom and by the end of the day the beetles had eaten and destroyed all the flowers. We now use a yard service that comes out several times during the spring and summer. They have gotten rid of all the grubs and we have been beetle free since then!