Japanese Beetles Populations Expected to Peak Later in July

FROM UNIVERSITY OF MISSOURI EXTENSION
SOUTHWEST REGIONAL NEWS SERVICE
Contact: Sarah Kenyon, agronomy specialist
Headquartered in Texas County
Tel: (417) 967-4545  
E-mail: kenyons@missouri.edu

HOUSTON, Mo. -- Japanese beetles have been reported in large numbers across Missouri according to Sarah Kenyon, agronomy specialist with University of Missouri Extension.

“These destructive insects feed on roses, shrub, vegetables, and even field crops like corn and soybean.  The damaged leaves typically look like Swiss cheese,” said Kenyon.

Trap counts across the state indicate the population will continue to climb and will peak later in July.  The green, dime-size beetle with bronze wings and white tufts of hair around its shell is amid a multi-year population boom.

Japanese beetles show little discrimination in filling their stomachs, and will feed on any plant that has a pleasant smell.

“Roses and linden trees are their favorite crops, but they’ll feed on a wide variety of ornamentals, fruit trees, grapes and 440 different plants species,” said MU Entomologist Wayne Bailey. “They usually feed on the tops of plants in the sunlight, and they like plants that smell succulent, so if it smells good to you they likely will prefer those plants.”

Field crops also appear on the menu for the Japanese beetle.  Both corn and soybeans can receive significant damage if control measures aren’t implemented.

This can be a serious pest for corn farmers.  The insect will chew on corn silk and tassels.  If the silks have been taken down to less than half an inch in length, there will not be any pollination, resulting in poor corn production.  In corn, treatment is recommended if there are three or more beetles per ear that are producing green silks and pollination is less than 50 percent complete.

In soybean crops, Japanese beetles chew at the leaves. They prefer lush leaflets at the top of plants and can hurt yield by significantly defoliating the plant.  Control is justified if there is 25 percent damage to the leaves of soybeans.

Japanese beetles live for one year.  The adult lays eggs in July that hatch and develop into white larvae, which overwinter in the soil and mature during the spring.  They emerge as beetles in mid-June and begin feeding.  Each healthy female lays 40 to 60 eggs.  Adults live up to 60 days.

Homeowners can fall back on a staple insecticide, powdered Sevin (carbaryl), to combat the destruction of Japanese beetles.  “Sevin is probably one of the best, because it’s readily available and relatively safe to most everything around,” Bailey said.

More for information on the insect contact MU Extension Agronomy Specialist, Sarah Kenyon at 417-967-4545 or by email at KenyonS@missouri.edu.
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