Black spot is also a leaf spot disease that is best prevented. Forget about milk or baking soda being an effective control, studies show that below the upper parts of the US it doesn't work. Copper is somewhat effective, so are products with myclobutanil, which is a systemic fungicide, and combine it with Mancozeb, which is contact fungicide. If you spray Mancozeb three times, three days apart, spray ground and old leaf debris, and this will get black spot under control. Don't forget about contacting the American Rose Society www.rose@org, and look up a Consulting Rosarian for advice too. There was a new organic product I saw at a recent ARS national convention called Rose Shield. The company gave out free spray samples. Will try it and hope it works. I'm in the northeast side of South Carolina.
