The Purdue Plant and Pest Diagnostic Laboratory

Japanese Beetles

The following questions were sent to the P&PDL diagnosticians here at Purdue University:

Question 1: I have had some SERIOUS problems with japanese beetles in my yard. They have been attacking some of my trees, and if it hadn't been for me squishing them with my bare hands, I'm SURE that I would have lost some of my trees. The main trees that they were attacking were my pussy willow trees, and my plum trees. I didn't know what to do. I used the BAG-A-BUG trap, and it seemed to work for a little bit, but there were just TOO MANY BEETLES!! Please e-mail me back, and tell me what I can do to solve my problem.

Answer 1: You can read more about Japanese beetles in Purdue's extension publication, E-75. Available at the following URL:

Question 2: We live waaaaaay out in the country, surrounded by acres of fields. Each year, we seem to have more and more Japanese beetles infesting our roses and strawberry plants, as well as a number of other plants. Spraying malathion or Seven helps temporarily, but they JUST KEEP COMING!!! Is there any way we can slow down or stop the infestation and save our roses?

Answer 2: It sounds as though you are doing the best you can do. Repeated chemical applications (malathion or sevin) is the best control against Japanese beetle populations. Also, if you want, you can replant plants that are resistant to these beetles. Besides the controls given, there is little you can do to slow down the Japanese beetles. Good luck!

-- Corey Gerber

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