How to Kill Black Spots on Hedges
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.
- Prevent black spot by eliminating above ground irrigating and instead water near the base of the hedges when possible. Furthermore, remove leaves and other plant debris that have fallen to the ground regularly.
- Do not apply horticultural oil to water-stressed hedges. It will cause more harm than good. If plants are stressed, treat that problem first before dealing with the black spot disease.
Marylee Gowans has written about gardening for both online and print publications. She attended the University of Akron, graduating with a Master of Fine Arts in creative writing. In 2009, she received master gardener certification from the Master Gardeners of Summit County, Ohio.