Apple Cider Vinegar Fungicide: for leaf spot, mildew, and scab. Mix 3 tablespoons of organic apple cider vinegar (5% acidity) with one gallon (3.8 liters) water and spray in the morning on plants. Good for black spot on roses and aspen trees, too.
Baking Soda Spray: natural, non-toxic anti-fungal spray
Baking soda has been found to possess fungicidal properties. For plants that already have powdery mildew, hosing down all the infected leaves prior to treatment is recommended. This helps to dislodge as many of the spores as possible to help you get better results. Use as prevention or as treatment at the first signs of any of the diseases.
To make: Mix 1 tablespoon baking soda, 2 1/2 tablespoons organic vegetable oil with one gallon of water. Optional: add 3 – 5 drops of essential oil of tea tree or lavender. Shake this up very thoroughly. To this mix add 1/2 teaspoon of pure Castile soap. Be sure to shake your sprayer while you work to keep the ingredients from separating. Cover upper and lower leaf surfaces and spray some on the soil. Repeat every 5-7 days as needed.