The No. 1 disease responsible for harming roses is blackspot. Roses affected by this fungal disease may exhibit dark brown spots on the foliage and eventual loss of the leaves.Since not all roses are susceptible to blackspot, the best approach is to select a cultivar that is resistant to this harmful disease. However regular treatments with fungicides, beginning just as the buds begin to swell in early spring and continuing throughout the growing season, will help prevent them.
Although there are a number of potent fungicides on the market, nothing beats this homemade recipe: Mix together one tablespoon of baking soda and 2-1/2 tablespoons of highly refined horticultural oil in one gallon of water. Spray a little on lower leaves before covering the entire plant to make sure it doesn't burn the foliage. If it does, use half as much baking soda. That's it.
Another prevention method is to use a solution of half skim milk and half water. When sprayed on the foliage of roses, it prevents mildew and blackspot from growing. Spraying for blackspot should be done in the morning so the leaves will be completely dried in the sunshine. The skim milk forms a thin film over the leaf and prevents blackspot from developing.
Note: When spraying for blackspot, be sure to spray both sides of the leaves because it originates along the undersides of the leaves.
Without a doubt, however, the most important disease-prevention step you can take is practicing good garden sanitation. That means getting rid of fallen leaves as soon as possible and applying fresh mulch to smother any overwintering fungal spores.
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