How to Treat Black Mold on Citrus

Identify the insect infestation. The citrus sooty mold fungus (Capmodium citri) appears on giant whitefly- or scale-infested trees. Scales appear as white, gray or reddish-brown, flat to slightly oval growths on citrus twigs, leaves and bark. Giant whiteflies typically feed on leave's lower surfaces. The mothlike adults deposit telltale wax trails when they walk.

Treat scales with a horticultural oil on a clear, dry, late spring or summer day. Cover foliage surfaces, twigs and bark thoroughly with the spray.

Treat light whitefly infestations by removing the affected leaves with pruning tools. Place the leaves in plastic trash bags. Seal the bags and dispose of them away from the citrus trees.

Spraying the affected trees with the garden hose controls large, giant white fly populations. Aim concentrated blasts of water at the leaf undersides at least once every week. After the pests' numbers decline, continue spraying at two- to three-week intervals. This practice is called syringing.

Remove the sooty mold remaining after eradicating the insects. Wash it off with the garden hose. Alternatively, simply wait for the honeydew-deprived mold to weather away.