Hello,

You state you have a "big infestation of Japanese beetles" in your neighborhood. Okay, but what plants specifically are your worried about? Most can take a period of Japanese beetle feeding without any permanent damage. Japanese beetles can fly great distances, so trying to completely eliminate them from your neighborhood is an exercise in futility. I am not certain at what distance away from the desirable plants would be safe to place those beetle traps, which have been found to attract 30-40% more beetles to your area. 

The more effective control method might be targeting the grubs in the lawn and yes, August - September and then late March - early April are the periods when grubs are active and near the surface of the turf. You would need for your entire neighborhood to get on board with grub control to effectively reduce the entire population of the neighborhood.

Recommendations for management of Japanese beetles can be found here and grub control can be found here.

Marie