Eliminate sooty mold by treating the aphids, killing the ants that farm them and wiping the powder off the plants with a mild detergent solution. The problem forms due to the honeydew the aphids create when eating the plants. Eliminating the aphids usually solves the problem.
- Treat the aphids
Use a soap-oil spray you create at home by mixing 1 tablespoon of cooking oil with 1 tablespoon of mild dishwashing liquid with a cup of water. Put the mixture in a spray bottle, and spray the leaves weekly in the early morning. Pay careful attention to the underside of the leaves.
- Kill the ants
Kill the ants with an approved insecticide to prevent reinfestation. If using ant bait, remember you must keep it dry for it to remain effective. Ants feed on the honeydew the aphids create. They move aphids from one location to another to improve honeydew production.
- Wipe the soot from the leaves
Mix a solution of mild dishwashing detergent and water. Use a rag to wipe away the soot from the plant. While it normally does not cause problems and goes away if you deal with the underlying source, heavy infestations of sooty mold interfere with photosynthesis. Wiping away the soot exposes the leaves to the sun to improve plant growth.