Black spot
Diplocarpon rosae
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How to spot it
Black spot is the most important leaf disease on roses. Characteristic are the black spots with star shaped frayed edges, around which the leaf turns yellow. Badly infested roses lose their foliage early, weaken and flower less. The fungus overwinters in the fallen leaves and on the shoots.
Prevention
Choose robust, ADR tested rose varieties and plant them airily, so that the foliage dries off quickly after rain. Collect the fallen leaves consistently in autumn and dispose of them with the residual waste, not on the compost. Strengthening the plants with horsetail brew and cutting back infested shoots slow the spread.
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