When black spot is on a plant, the leaves can begin to fall off. Some plants become completely defoliated, but if cared for, will survive. Black spot lesions on the rose canes are small and seldom kill the plant, but are important in the survival of the disease over the winter. If possible, do not water plants overhead with sprinklers. Leaves must not be allowed to remain wet or in high humdity for more than 7-12 hours.
Sanitation is extremely important in controlling black spot.
Remove leaves from the ground and prune canes that have lesions to reduce overwintering of the disease. Fungal sprays can be used during periods of the year when conditions are favorable for black spot. Preventive spraying can begin in March until leaves are mature, then spray fungicide as needed. Compendium of Rose Diseases. Wade, G., J. Midcap, W. Corley 1995.