This mold is created as a direct result of insects such as aphids, scale, whiteflies and mealybugs. They suck the sugars from the plant, leaving a great deal of this nectar behind on the leaves of the plants being attacked. This sticky substance covers the leaves and provides nutrients for the mold to grow. This fungus interferes with photosynthesis, reducing the energy level of the plants being attacked. Ants too play an important role since they heard many sucking creatures around from plant to plant.
Ants also have their own fungus which they carry on the bodies.
This fungus will also grow on the nectar left behind by the sucking insects. Also other insects will come around to feed on this nectar. The two main ingredients are Castile soap and citrus oil.