Sooty Mould

Plants/trees Affected

Trees, Shrubs, Palms and indoor plants.

                         

Symptoms

Leaves, stems and branches are covered with black sticky patches, they are saprophytic (ie remain on the surface and do not invade or feed off the plant). The mould prevents light and air getting to the leaf surface which interferes with the photosynthesis process, a vital part of the plants survival. If untreated it could result in the yellowing of leaves and stunted growth.

Causes

This is a secondary disease where the sooty mould fungus grows on honeydew, the sticky substance secreted by sap sucking insects like aphids, scale insects, mealy bugs and whitefly.  The fungus survives best in dry conditions as rain will wash the honeydew off the foliage.

Prevention

Sooty mould can be prevented by identifying the cause of the honeydew residue which falls on the leaves.  Treatment of the sap sucking insect infestation will stop the onset of the mould.

Treatment

• Sooty mould can be washed off the leaves with just water or soapy water if necessary and does not require any chemical intervention.