Today 
A fungal disease weakens the plant and can seriously reduce its flowering performance. The brown spots eventually grow together and develop grey centres. Infection is caused by air or water-borne spores entering the plant through damaged leaves. In wet weather the fungus spreads quickly. The spores are persistent and overwinter in the soil and on old leaves, stems and rhizomes.
Solution
Organic
Healthy plants are less likely to succumb to an attack. Clear away leaf debris lying on the ground around the plants. Take care not to damage leaves and stems unnecessarily.
Chemical
At the first sign of trouble, spray leaves at fortnightly intervals with a multi-purpose fungicide containing carbendazim.
