How to Cure Black Spot on Roses
- 1). Prune infected leaves and canes, discarding them in the trash. Rake the area surrounding the rose shrub to remove any infected plant debris that might have fallen on the ground. Do not recycle this material, as composting doesn't kill the fungus.
- 2). Blend 2 tsp. baking soda, 2 drops seaweed extract, 2 drops liquid dishwashing detergent and 5 quarts water. Stir the mixture and add it to a spray bottle. Spray the solution on all areas of the rosebush with black spot to kill the spores.
- 3). Add 1 gallon of well-rotted manure to a 5-gallon bucket. Fill the container with water and stir. Place the bucket in a warm area and let the manure steep for three days. Strain the manure tea with cheesecloth, scooping out enough to fill a spray bottle. Spray the infected plant tissue with this formula to kill the fungal spores.
- 4). Use a low-toxicity fungicide on infected rose shrubs. Select a product containing neem oil, sulfur or copper as its active ingredient. Apply it according to the manufacturer's label.
- 5). Spray a rose bush suffering from black spot disease with a synthetic fungicide. Select a product containing trifloxystrobin, maneb, triforine or another chemical labeled for use on roses with black spot. Follow the application method, rates and schedule indicated in the manufacturer's instructions for the brand you select.
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