Roses are one of the most beautiful and widely cultivated flowers in the world because of their delicate nature and romantic portrayal. Roses, being as delicate as they are, are susceptible to fungal diseases. There are several ways to treat roses organically to rid the flower of fungal infection.
Horticultural oils can be used to control pests on roses that can cause and spread fungal infections. Powdery mildew that can spread rapidly can be controlled by using diluted horticultural oil mixed with baking soda, then sprayed over the rose plant with a hand-held sprayer. This will effectively starve pests on the plant and prevent further spread of mildew.
The most effective organic treatment for fungus is prevention without the use of any spray, organic or chemical. Cleaning up rose bushes in the fall will prevent the spread of fungal diseases such as black spot. Removal of all infected leaves that have fallen from the plant, laying in the soil, as well as the pruning of diseased canes from the rest of the plant will keep disease from spreading during the winter and further sporing of fungus in the spring.
Sulfur can be used as an organic fungicide spray to prevent and control the further spread of infection. Sulfur should be used throughout the season. Spraying of the leaves and canes of the rose plant is required to prevent spread. Unlike some fungicides, sulfur does not have a lasting effect, and must be sprayed regularly to prevent fungal infection. Spraying weekly, as well as before rains, is usually enough.
Another organic method of fungal control is good air circulation. Roses should have plenty of clearance between other plants, as well as buildings or other structures. Roses that do not dry quickly enough have a higher risk of fungal infection like black spot, and spread disease quickly through close habitation.
Good rose care will prevent the spread of fungal infection as well. Overwatering will splash the spores of fungus and allow it to spread. Once the early summer has ended, and favorable black spot conditions have passed (cool, wet weather), blasting the leaves and petal of the rose bush with a hose will remove insects and powdery mildew.