Japanese beetles can be controlled by various methods including chemical spays, traps, physical means, or a special organic bacteria for long term control.

The most effective chemical control is liquid Sevin, which must be  applied every 4 to 5 days for complete control. New beetles will continue to hatch out of the ground for a period of about six weeks during the summer, so continue a regular spray or dusting schedule.

Japanese beetles can also be controlled by using beetle traps, however, they must be placed at least 15 to 20 feet away from the plants the beetles are feeding on. If the traps are too close to the plants, the beetles will be attracted to the plants rather than to the traps.

If you do not want to use chemicals in your garden, you can control Japanese beetles by knocking them into a bucket or pan of soapy water with a stick. They will be unable to fly out of the soapy water and will drown eventually. This procedure is best done in early morning or late afternoon when the temperature is cooler and the beetles are less likely to fly away from the plants.

Another non chemical control for Japanese beetles is a naturally occurring bacteria called Milky Spore. This bacteria kills Japanese beetle larvae (or grubs) which feed underground on grass and plant roots during the spring, fall, and winter. It is not harmful to beneficial insects, pets, or children. The bacteria spreads slowly through the soil to continue killing beetle larvae for many years. It will not kill new beetles that fly into the garden during the summer, only the larvae that are already in the soil.

Milky Spore is sold as a dust or granular material under the commercial names of Doom, Grub Attack, or Grub Killer. It is more effective in warmer areas of the country where the soil temperature remains above 70°F during the summer. This area includes the lower half of hardiness zone 6 through zone 10. Milky Spore is best applied in the spring or fall while the beetle larvae are in the ground.