Black spot

Rose black spot is very similar and can be dealt with in the same way.

Symptoms

Leaves are marked with purple or brownish-black spots, then turn yellow and fall. Smaller marks sometimes also blotch the stems. Plants can be weakened by regular attacks.

Find it on

shrubs, roses

Organic

Fallen, affected leaves must be promptly destroyed, along with any stems showing signs of infection. The best way to avoid the problem - which thrives in warm, wet conditions - is to lay a thick mulch around the plant. This helps lock moisture in the ground, and stops rain splashing the spores from the soil on to new growth.

Chemical

Spray with a fungicide containing myclobutanil. Begin spraying each fortnight from early spring, just as the new foliage emerges, as a preventative measure.