Black mold (often called sooty mold) is a fungus that infects bushes, coating the leaves and branches with a thin layer of dark gray or black mold. It can be caused by just one fungus or several of them, and occurs when sucking insects infest your plant. The insects excrete honeydew, a sticky substance that fungal spores land on. The mold can appear soft, like velvet, or it can be hard and crusty.
This fungal disease is unattractive, and severe infestations may stunt the growth of your plant or cause it to wilt--but black mold is not deadly.
Clear the area around your bush, if possible. Exposure to sunlight and air helps lessen, or even stop, the growth of fungi.
Rinse off the mold with a strong spray of water. Add a teaspoon of liquid soap to the spray to help aid in cleaning the bush. Test an area of the bush first to see if the soap will damage it. Spray a few leaves, then wait a week. If the leaves appear unchanged, blast the entire bush with water until as much of the mold is rinsed off as possible.
Get rid of the underlying cause of the mold. Examine your plant for chewing or sucking insects such as aphids, scale, or mealybugs. Look for a sticky residue (honeydew) on the leaves or around the bush. Ants feed on honeydew, so a large population of ants in and around the bush is another clue.
Spray your bush with an application of insecticide. You may need to re-apply the poison a week to 10 days after the first application in order to completely rid the plant of the insect pests. Monitor your bush carefully, and treat it again at the first sign of insect pests.