Answer: Summer Wine is considered to have fairly good mildew resistance, but mildew is fairly common on ninebark when weather conditions are conducive to it. Once mildew appears, it generally can not be controlled by spraying. The spraying would be done on a preventive basis next year to prevent it from recurring. Other steps to take would be to thoroughly clean up all fallen foliage this fall and dispose of it in the trash, thin the plant to promote air circulation through it, and be sure it is planted in a location with good air circulation. Also avoid wetting the foliage if you water it, and if watering is needed try to do that in the morning so the foliage is not damp in the evening or at night. You might also want to consult with your local county extension just to confirm the diagnosis. They should also be able to make control recommendations. I'm sorry you are having trouble with your ninebark. Hopefully next year the conditions will be different and it won't be a problem.
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