Leaf spot is a condition caused by fungus and bacteria that result in dark, black splotches to form on the leaves of infested plants. These spots are mainly a cosmetic issue, but severe cases can be detrimental to the plants health. Luckily, it is easy to cure black spots on plants using homemade antibacterial and fungicidal solutions to kill the spots at their source.
Combine 3 tbsp. of apple cider vinegar with 1 gal. water in a lawn and garden sprayer. Spray the plants with the vinegar mixture every morning until the black spots disappear.
Spray down the infested plant with water from a water hose. This will loosen the fungus's hold on the plant. Mix 1 tbsp. baking soda, 2 1/2 tbsp. vegetable oil, 1/2 tsp. of castile soap and 1 gal. water in a garden sprayer. Thoroughly cover the plants with the mixture once weekly until the spots dissipate.
Simmer 8 oz. of elder leaves in 16 oz. of water for 30 minutes. Strain the leaves out and combine the liquid with 1 tbsp. of castile soap and 16 additional ounces of water. Mix well and apply to afflicted plants and spray once weekly until the black spots are cured.
Mix 3 oz. minced garlic with 1 oz. mineral oil and let it soak for one full day. Strain the garlic out and save the garlic oil in a glass container. Combine 1 tsp. fish emulsion with 16 oz. water and store in a glass container. Mix 2 tbsp. garlic oil with 1 oz. fish emulsion and spray on afflicted plants to cure black spots.
Combine one part milk with one part water in a lawn and garden sprayer. Spray the infested plants with the mixture once every three to four days to get rid of black spots. Similar to apple cider vinegar, the milk changes the acidity of the surface of the leaves, making it harder for black spots and fungus to take hold and live on the plant.