The black coating is called Black Sooty Mold, a simple mold that grows (and feeds on) the sticky, sweet excrement of different piercing/sucking insects. The usual culprits are aphids, scale insects, whitefly, leaf hoppers, and mealybugs.

Is this the same plant in the other post? If so, you know who is the guilty party.

The BSM is benign...the insects are the problem. Get rid of the insect pests and the mold will go away on its own.

Thank you.

Did you purchase the Immunox you mentioned in the other post for the BSM? If so, that's what I meant about prescribing heavy duty meds for a headache, when all that's needed is an eyeglass adjustment.

The black mold isn't even growing on your plant.....its feeding on the sugars that the scale insects are creating as they feed on the plant.

BSM can grow on anything upon which that honeydew falls; the walls, floor, patio furniture, etc. can all become covered with the unsightly stuff. It should never be treated with a fungicide.

Once you get rid of the scale, the mold will go away on its own.