Japanese Beetles - Knowledgebase Question

Liverpool, Ne
Avatar for dgiarro
Question by dgiarro
August 6, 2010
I wanted to find out if spraying my plants with a soap and water mixture will hurt my rose bushes and shrubs? I read that soapy water was a way to kill japanese beetles but I don't want to harm my plants. Thank you for your help.

Answer from NGA
August 6, 2010
Extended use of even gentle products may cause problems for plants. Insecticidal soaps aren't very effective against Japanese beetles, so I imagine that dish soap is less so. I've found that rose bushes are especially sensitive to the fatty acids in soaps which can burn the leaves. I'd use a product especially formulated for roses that is proven to control Japanese beetles. Rose Defense is one such product and it is safe to use on other shrubs, as well.

It often takes a two-pronged approach to control Japanese Beetles. You are seeing the adults which were grubs in your lawn and garden earlier this year. So, you'll want to control both the adults you're seeing now, and any grubs that may overwinter in your soil. Milky spore, Bacillus popilliae, is a disease-causing bacterium that is effective against grubs of Japanese beetles. Be sure to apply according to label directions.

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