‘Sooty mould’ is a generic term for all sooty moulds caused by numerous Ascomycete fungi.
It includes genera and species from around 14 families.
Among the most common are Alternaria and Cladosporium species.
Sooty mould grows on plants such as azaleas and camellias.
It also grown on objects like fences and stones.
A plant is susceptible to infection if it is infested by sap sucking pests.
Examples are aphids, scale insects, mealy bugs or whiteflies that produce honeydew.
Occasionally a plant itself produces a sugary exudate.
Sooty mould is a black or dark brown area usually on the upper surface of leaves.
It may be a thin dusting or a thick layer that cracks and peels off.
Spores of all species are dark.
Sooty moulds cause little harm to the plant and is mainly a cosmetic problem.
If there is a thick layer of fungus it may reduce photosynthesis due to lack of sunlight.
J.F.
