Mango sooty mold (Meliola mangiferae) is one of the species of fungi that grow on honeydew results from interactions among sap-feeding insects such as soft scale (wax, green and cottony cushion scales), mealybugs, aphids, whiteflies and treehoppers and non-parasitic fungi. The fungi just leave some cosmetic damage on tree and do not infect the plant tissue. However, they impact plant photosynthesis and growth negatively by blocking sunlight from reaching leaf chloroplasts.
Symptoms: As parasitic insects use the sugary honeydew as a food source, the sooty mold fungi begin to grow on the sugars left by insects on the foliage, turning the leaf surface to black. It means that any plant that is host for sap-feeding insects, is susceptible to sooty mold.
Damage: Gas exchange and photosynthesis reduction, cosmetic damage, reduced marketability, reduced fruit quality in juice processing
Control: The best way to control sooty mold fungi is using preventive method by eliminating their sugary food supply. Controlling sap-feeding insects on the foliage as well as ants that tend and protect them. As soon as sooty mold is observed, insect control should be started. The type of insecticide depends on the plant and target pest. General-purpose fungicide may be effective on killing fungi but not removing black color. Controlling ants by using barriers or insecticide baits is another control method. Pruning to remove most of the infested plant parts is helpful. If the tree is small, sooty mold can be washed off with a strong stream of water or soap and water.