Several species of fungi may
cause brown or black circular or irregular shaped spots on the leaves.
Infected leaves should be
removed and burnt and the plants sprayed with a fungicide such as Mancozeb
(Dithane M45, Manzion, Manzate). Sooty mould is a black fungus on the upper
surfaces of leaves, growing in the secretion of aphids, mealybugs, many scales,
and immature whiteflies. The mould spoils the appearance of foliage but is not
particularly injurious to the plant. Kill the insects and the problem will
disappear. Oil emulsion or miscible oil sprays will loosen the mould and help
clean up the plants. By spraying this material at about sundown, the dew helps
to free the sooty mould from the leaf, and a forcible stream of water from a
hose nozzle next morning before the sun dries the leaf will wash away 90 % of
the sooty mould. A fungicide such as Mancozeb may also be used.
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