Japanese Beetles

Garden Corner

What to do About Japanese Beetles

Japanese beetles were introduced to the U.S. in 1916 after accidentally being imported on the roots of iris plants. They have become a growing problem since that time as they have an abundant food supply, a favorable climate and no known native predators in the U.S. Japanese beetles pose many threats to various plants. In the larval stage they wipe out lawns by feeding on grass roots, in the adult stage they have been found to wipe out more than 300 species of plants including flowers, vegetables, fruits and a wide variety or ornamental trees and shrubs.

There are many ways to remove beetles from your gardens. Removing beetles by hand may provide adequate protection for small plantings; try shaking them off early in the morning, while they are still sluggish, into a bucket of soapy water, which can kill them. Highly valued plants, such as roses, can be protected by covering them with cheesecloth or other fine netting during the peak of beetle activity. Many insecticides are labeled for use against adult Japanese beetles. But before reaching for a toxic chemical that could also kill beneficial pollenators, look for more natural, earth-kind products such as Azatrol or Neem-Away (Gardens Alive), or Pyola (pyrethrins in canola oil) which keeps Japanese beetles from feeding on the plants for three to four days. Be aware that insecticidal soap, extracts of garlic, hot pepper or orange peels, and companion planting are generally ineffective.

Traps are also available commercially, however research conducted at the University of Kentucky showed that the traps attract many more beetles than are actually caught. Consequently, susceptible plants along the flight path of the beetles and in the vicinity of traps are likely to suffer much more damage than if no traps are used at all. In most landscape situations, use of Japanese beetle traps probably will do more harm than good. If you experiment with traps, be sure to place them well away from gardens and landscape plants. Because Japanese beetles are attracted to favored host plants from a considerable distance, controlling their grubs in the lawn will not protect landscape plants from adult feeding.

For more information check out; www.utextension.utk.edu/publications/pbfiles/pb946.pdf