Prevalent during periods of excessive rain, black spot disease is a fungal pathogen that can affect trees, ornamental plants, crops, shrubs and hedges. Plants infected with this fungal disease will develop black spots on the leaves and stems, and infected leaves may drop from the branches. If not treated, the fungal spores causing black spot disease will spread to nearby plants. If possible, begin treating black spot disease as soon as you notice signs of infection. Once treatment begins, take the necessary precautions to prevent this and other fungal diseases from returning.
Dissolve 4 teaspoons of baking soda in 1 gallon of lukewarm water. Stir for several seconds with a wooden stir stick.
Add a 1-percent solution of horticultural oil to the mixture. Stir for several seconds with the wooden stir stick.
Transfer the baking soda mixture to a clean pump sprayer. Spray the hedges thoroughly with the baking soda mixture, trying to avoid open blooms. Continue spraying until you have covered the hedge with a liberal amount of the mixture.
Repeat the treatment 7 to 14 days until you have the black spot disease under control.