The Q&A Archives: Using Liquid Soap to Combat Japanese Beetles

Question: I have 8 grapevines and they have been attacked by Japanese Beetles. I'm trying to get rid of them by both handpicking and spraying heavily with liquid dishwashing soap mixed with water. I was wondering if too much soap will damage my plants, or the roots. I spray heavily about twice a day.

Answer: 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. Water the soil around the vines well to dilute the soap that has accumulated there. What happens if you spray plain water? Does that also cause the beetles to depart? It may be as effective as using soap. Have you considered covering your grape vines with fabric row cover to exclude the beetles? The cost of the fabric should quickly pay itself back in the time and energy you'll save. Contact Gardener's Supply Co. for sizes and pricing (; 800-863-1700) or check your local garden center. Best of luck to you!

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