In our area milky spore is generally not recommended since it only controls Japanese beetle grubs and not our predominate lawn grub, annual white grub. Also Japanese beetle grubs must already be infesting the turf for milky spore to work effectively. Pesticides commonly used for lawn grub control such as diazinon will also control Japanese beetle grubs. However, according to Phil Nixon in the U of I Extension Home, Yard and Garden Pest Newsletter , controlling Japanese beetle grubs does not significantly reduce the number of adult beetles the following year. The beetles are good fliers and easily fly a couple miles in a single flight.
Evidence suggests that adult beetles are attracted to previously damaged leaves.
Therefore reducing feeding damage now can result in less feeding damage in the future. Generally pesticide sprays of cabaryl sold as Sevin can reduce damage for up to two weeks. Sevin is toxic to bees and other beneficials. Synthetic pyrethroids can also be effective. The Japanese beetle repellent made from Neem has not been shown to be effective.