How to Remove Japanese Beetles from Your Japanese Maples
This is a very common question we at MrMaple get, year after year. The biggest mistake people make is setting up alot of bug traps, it's counter-intuitive to do this if you have a smell infestation. The traps will catch females which release pheromones that will in turn attract a lot of Japanese beetles to your area. While it may subdue alot of them, you'll notice a huge increase of your problem.
The best solution for a small infestation of Japanese beetles is to manually pick them off and dispose of them. However, female Japanese beetles, again, will leave pheromones on the plant, which may attract males back to the plants. To resolve this secondary issue, get mildly soapy water and spray down the plants that housed the beetles to wash away the pheromones.
As a last resort option for larger infestations or if the above tactics didn't resolve the issue, you can use insecticides. In the past we've had good results from using spectracide triazicide for large infestations. Always follow the safety procedures for whatever insecticide you plan on using. Once again, ensure you spray mildly soapy water on the plants you used the insecticide on afterwards to clean any left-over chemicals off.