Sooty Mold

This fungus grows on the honeydew produced by sucking insects (aphids, leafhopper, whiteflies and more) and affects a wide variety of plants (including peppers, tomato and citrus). It doesn’t actually infect the plant itself, but is detrimental because it coats the leaves and reduces photosynthesis. This can cause leaves to die prematurely and drop, which can result in slower growth.

To control sooty mold you need to control the insects creating the honeydew. The simplest way to do this is to wash them off the plants with a strong jet of water. If this doesn’t work try insecticidal soap or neem. Ants are often the cause of aphid infestation and may need to be controlled too. The mold can be hard to wash off, but eventually wears away.

Image: Brian Kunkel, University of Delaware, Bugwood.org