Did you have a problem with Japanese Beetles last growing season? NOW IS THE TIME OF YEAR TO GET RID OF THEM BEFORE THEY EMERGE! The Japanese Beetle grub is at the surface of our grass and garden soil right now feeding on roots. However, before applying an insecticide for grubs, make sure you have a large infestation. Look for areas of brown turf and search in adjacent green areas for grubs and pupae. Insecticides are needed to control grubs and adults if the damage is extensive. If you treat the soil in your lawn and garden, you can kill them off before they emerge. Less grubs= less beetles chewing your plants in June and July!!
Sunnyside Gardens carries a chemical control and an organic control to get rid of these pesky grubs! The Bonide Grub Beater granual is ideal for use on turfgrass and landscape ornamentals. The best time to apply is March through early June when the grubs are still underground. A second application of Grub Beater is recommended late August through late October. This will kill any grubs that were laid by the adults this summer, and help prevent beetles the following summer.  Milky Spore is an organic product that will kill the grubs naturally over a couple seasons. Irrigating after applying an insecticide improves its insect control.
http://www.ehow.com/how_8129399_can-kill-japanese-beetles.html