Star soot is a dreaded disease among gardeners, which mainly affects laurel, oleander and roses. Black spots that spread on the upper side of leaves and eventually turn them yellow indicate soot dew.
Many gardeners do not plant roses simply because they fear that the plant could be attacked by the soot. The black dots not only look unattractive, they also weaken the rose, as it loses more and more leaves over time. Fertilizing with potassium-rich fertilizer also prevents infestation.