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Terry L. Yockey, Goodhue County Master Gardener
Last season Japanese Beetles invaded Minnesota in a big way and unfortunately now that they have arrived, they are here to stay. Though they are fairly new to Minnesota, the first transplanted Japanese beetle was found in a New Jersey nursery in 1916. As the name implies they are native to Japan where they have several natural enemies that keep their population in check. Here in the U.S., however, Japanese beetles continue to spread to new areas every year and have become a highly destructive plant pest.
In mid to late-June female beetles emerge and begin feeding, mating and burrowing into the ground where they lay their eggs. The eggs hatch into grubs in about two weeks. The grubs grow quickly feeding on the roots of turf grass and are almost full-grown in August. As fall approaches and temperatures cool below 50⁰F the grubs dig deeper into the soil to overwinter. When spring arrives and the soil warms again they begin to move upward and resume eating. In mid-June the grubs pupate and the adult Japanese beetles emerge one to three weeks later.
Biological and Non-Toxic Controls
Adult Japanese beetles feed on over 300 different plants including trees, shrubs, annuals and perennials. Once Japanese beetles become established they are very difficult to eradicate so vigilance and using a variety of different control methods is crucial to their management.
Here are six non-chemical control methods:
There are several chemical insecticide sprays on the market that are effective against Japanese beetles, but most are toxic and harmful to birds, butterflies and other backyard wildlife. For more information on using chemical controls for Japanese beetle adults and grubs, please see the UMN Extension fact sheet at www.extension.umn.edu/distribution/horticulture/dg7664.html.
Posted by tlyockey on December 4, 2010 11:16 AM in Popular Topics