I've never noticed any problems with Japanese beetles around my yard - I never really thought much about them until recently. Last year I had a wheelbarrow of compost and soil sitting in the yard for an extended period, and, when I went to use it, it was full of Japanese beetle larvae. It was really fun feeding them to the chickens - they loved them! I never thought I had many in the yard, but I found one recently while pulling weeds.
What are japanese beetles and why don't we like them? As the name suggests they are originally from Japan, hence they are one of many non-native insects that have no natural enemies to keep their population in check. As adults, they have huge appetites, feeding on the fruit and leaves of more than 200 different plants. They are identified by their green body and copper-colored wing covers - they also have white spots around the abdomen.
What can be done about them? Some adults beetles will be eaten by birds, but not in significant numbers. There are traps, but a large numbers of them would need to be set out, and there is evidence that these actually attract more beetles to the area. There are sprays that control adult beetles, but you may have to spray numerous times to be effective. Another strategy is to control the grubs. There are insecticides that you can spray on your lawn, but will provide only temporary results. A long-term strategy for grubs is biological control. They are highly susceptible to something called milky spore disease. It is caused by a bacterium and is very specific to japanese beetle grubs. It may take a few years to become established, but the bacterium will be effective for 20 years or more. For more detailed instructions dealing with Japanese beetles, please visit this link.