Black spots on rose leaves are caused by the black spot fungus Diplocarpon rosae. Not only does it make the plant look unsightly, but it also causes the leaves to drop prematurely, which weakens the plant if it occurs repeatedly. The fungus spends the winter on the stems of the rose and on fallen leaves.
Additionally, how do you treat black spot?
Organic methods for dealing with rose black spot
Pick up and destroy fallen leaves. When pruning, cut out any stems with black spot on. In late-winter, spread a thick layer of mulch around the base of the affected plant to prevent rain splashing soil-borne spores on to new spring growth.
Just so, should I remove black spot leaves?
If left unchecked, the loss of leaves can weaken your plants and inhibit bloom development. Black spot usually won’t kill your plants during the first year or two, but if it continues unabated, it will make them more susceptible to other diseases and unable to survive harsh winters.
