Feeding is normally in the upper portions of trees. Beetles prefer plants in direct sun, so heavily wooded areas are rarely attacked. Adults are present until mid August. After mating females lay eggs in turf which hatch into grubs in August. Grubs feed on plant roots until cold weather drives than deeper into the soil.
Adults emerge in summer of the following year.
The bacterial control, milky spore sold as Doom or Grub Attack, is commonly recommended to control Japanese beetle grubs. 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.