Anthracnose is a fungal disease which shows up on roses as black small, circular spots with distinct and clear-cut edges. As the spots enlarge, the centre dries out and becomes grey. The centre may eventually fall out to give a shot-hole appearance. The leaves may yellow, but not to the same extent as in black spot disease of roses. Defoliation is not as serious either. Spots can occur on stems and flowers rarely. Spores are spread by wind and is worse in cool, humid conditions. Rosa Multiflora, used as rootstock is commonly affected.
Control is by improving air circulation around the plants and ensuring they receive sun almost all day long. Chemical control includes copper oxychloride spray or zineb sprays which are used to also target black spot.
Reference : McMaugh, pg. 219
Wonderful examples and good comment
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