News release: Japanese Beetles

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640
660-663-3232, bakert@missouri.edu

Release Date: August 31, 2017
Headline: Japanese Beetles

There are many examples of insects and diseases that are not native to North America which were introduced at some time to our continent.  Some of these pests did not have any natural enemies in North America, and they spread at various rates, totally unopposed.  A classic example of an introduced disease is Chestnut Blight, which essentially eliminated the native chestnut trees from the eastern United States.

There are many introduced insect pests, but one of the most well-known is the Japanese Beetle.  It was first found in New Jersey in 1916. Today, it is found in almost all the states east of the Mississippi River and quite a few states west of the Mississippi, including Missouri.

The first occurrence in Missouri was reported in 1934 in St. Louis. Today it is found in many other locations around Missouri.

Japanese Beetles are not picky eaters, and are known to feed on more than 400 species, including trees, shrubs, flowers, fruits, vegetables, field crops, and turf.  In high numbers, they can skeletonize leaves, resulting in a plant with only a framework of veins where the leaf should be.  They also feed on the roots of plants, including grass in lawns and golf courses.

Japanese Beetles have a complete life cycle, which means they have an egg stage, a larval (grub) stage, a pupal stage, and finally an adult stage.  Feeding damage is made by both grubs and adults.

They overwinter as grubs about six to eight inches below the soil surface.  In the spring they become active, feeding on roots.  After pupating, they emerge as adults in June, and start feeding again.  After mating, the females burrow into the ground to lay eggs.  A single female may lay as many as 60 eggs.

Japanese Beetle adults are metallic green in color, with copper-colored wing sheathes on their backs.  On each side of their abdomen, they have six white tufts.  They are not large, typically measuring about 3/8 inch in length.

Insecticides are available to control Japanese Beetles, but they can be difficult to eliminate because of their potentially large numbers and ability to feed on so many different kinds of plants.  Earlier, attempts were made to quarantine areas, but these proved futile.  Even trapping did not work, as it was found to actually attract more beetles to the area where the traps were located.

While Japanese Beetles have been in our Northwest Extension Region for over 15 years, they continue to move into new areas. In fact, I found one a few weeks ago at my house in Gallatin. That was the first one that I had seen in Daviess County.

For more information, I have included some links to several university resources on my web site.  Check them out at: http://extension.missouri.edu/nwhort/j-beetle.aspx