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Be on the Look-out for Japanese Beetle

Japanese Beetle:  Photo credit:  Jeff Hahn

University of Minnesota Extension, Stearns County News
August 2, 2017        
Source:  Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns, Benton, & Morrison Counties

Be on the Look-out for Japanese Beetle
By Beth Berlin, University of Minnesota Extension

ST. CLOUD, Minn. (08/02/2017) — If you have friends or family who garden and live in the Twin Cities area they have probably complained about the Japanese beetle. The Japanese beetle, Popillia japonica, has been in the United States since 1916 and present in Minnesota for decades. However, it wasn’t until 2011 that the population, especially in the metro area, reached levels that are causing problems.  This invasive pest is now on the move and even parts of outstate Minnesota should be on the look-out.

This summer there have been reports of the Japanese beetle in the St. Cloud area.  This is alarming because the Japanese beetle will feed on over 300 species of plants; some of their favorite plants appear to be roses, linden, grapes, and raspberries. Not only do flower gardeners have to be worried, but also vegetable and fruit farmers.  The adult Japanese beetle feed on the fruits and flowers, and skeletonize the leaves by eating all the leaf tissue only leaving the veins. Meanwhile the Japanese beetle grubs feed on turf grass roots and can cause damage to lawns as well.

Adult Japanese beetles are approximately 3/8-inch in length with a dark metallic green head and metallic tan wings. There are a few other species of beetles in Minnesota that have a similar description such as the rose chafer or false Japanese beetle. However the key characteristics that will set the Japanese beetle apart are two white tufts of hair at the rear of the beetle and five white lateral tufts of hair on each side of its abdomen below its wings.  Adults will emerge out of the soil in early July, feed, mate, and lay eggs. They will continue to be active for six to eight weeks and then gradually die off; however this is after laying eggs to generate the next population cycle. Over two months females can lay a total of 60 eggs.

If the Japanese beetle populations are still low, best management practices include hand-picking the beetles off the plants and putting them into a bucket of soapy water. High valued plants can be netted to exclude the pest. Once populations increase, hand-picking can be quite labor intensive and other management options may need to be considered. Low impact, short residual chemical products include neem oil and pyola. Longer residual products contain permethrin or carbaryl (Sevin). Caution should be used with all products, but special consideration should be taken to protect the bee population. Read and follow all application and safety instructions.

With all invasive pests it is often a matter of time before they reach your yard; it appears it is time to learn how to identify the Japanese beetle and exterminate them if found before the population reaches destructive levels as they currently are in the Twin Cities metro area.  For more information about the Japanese beetle visit and search “Japanese beetle”.

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