
Black Spot - Marssonina rosae- on a Rose leaf.
Black Spot - Marssonina rosae - on a Rose leaf.
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Black
Spot ( Marssonina rosae ) is a fungal disease that can attack the leaves of
roses. The rounded spots, up to 12mm (1/2in) in diameter, are generally worse during humid
weather. Affected leaves often turn yellow and fall prematurely. In the case of badly
infected roses, the new leaves will also bear the disease and eventually the entire bush
can be defoliated.
Black Spot on roses can be prevented, or at the very least the occurrence minimized, by
taking the following organic gardening precautions :
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Allow for the free circulation
of air around rose bushes and thereby reduce the humidity level. |
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Prune so that the centre of the
rose bushes are not congested. |
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Water at the base of roses and
not the leaves. This is particularly important when watering late in the day, as the
leaves will remain wet for an extended period. |
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Remove affected leaves and pick
up any that have fallen. Leaves from diseased roses should be placed in a bag and disposed
of. Never put the leaves from diseased roses into the compost bin. |
A simple home-made spray to prevent Black Spot on roses can be made from bicarbonate of soda, or a mixture of Chamomile, Chive,
Elder, Horseradish and Casuarina leaves.
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