Japanese beetle season picks up in Wisconsin

An image of Japanese Beetles on a flower

By PJ LieschUW Insect Diagnostic Lab

As July arrives in Wisconsin, Japanese beetles become active and can cause problems for gardeners, landscapers, and farmers. Activity often peaks in late July and August.

When Japanese beetles feed, they use chewing-type mouthparts to nibble small holes in plant foliage, resulting in a lace-like appearance; this damage is often referred to as “skeletonization”.  Other plant parts such as flowers and fruits can also be fed upon.  Overall, this damage can affect the aesthetics of ornamental plants and can also impact the yield of certain fruits and vegetables.

Japanese beetles can feed on hundreds of different types of garden and landscape plants, but some of their favorites include roses, lindens, birches, grapes, and raspberries.  Luckily, there are many different ways to manage these insects, including non-chemical approaches and organic options.  Check out Extension factsheet XHT1062 for guidance on managing Japanese beetles if they are causing problems in your yard or garden this year.

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