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They’re Back . . . Japanese Beetles

By Portage County Business Council

If you are seeing a lot of brown and green shiny insects around your yard lately you are not alone, Japanese Beetles are making their annual appearance in Portage county.

This nonnative beetle was first found in New Jersey in 1916 and has since spread to the Midwest.  The adult Japanese beetle feeds on over 300 varieties of fruits, vegetables, trees, shrubs and flowers, eating the soft tissue between the veins leaving a lace-like skeleton.

According to UW-Madison Entomologist, Patrick Liesch, we are going to keep seeing these insects through the end of August.  So what can you do?

  • Hand picking – The presence of beetles on a plant attracts more beetles- Daily removal will reduce the number by ½ compared to plants that allow the beetles to accumulate. Beetles can be killed by knocking them into a bucket of soapy water.
  • Chemical control – Many landscape sprays will control adult beetles but may need to be applied every 5-10 days. Read the product label.
  • DO NOT USE TRAPS! – Although they capture thousands of beetles research shows that plants near traps get much more damage than plants in areas of with no traps. Beetles are drawn into trap areas and those that are not captured are more likely to lay eggs in turf areas nearby.

For information regarding this or other questions contact the Portage County UW-Extension office, 715-346-1316 or

Submitted by Denise Rocha, Portage County UW-Extension Office.