Black Spot

I am often quoted as saying, when pressed on the subject, “what are a few black spots among friends?” A few black spots are not that unsightly and the fact that a rose may get black spot should not be a reason for not growing it.

The disease is usually most noticeable from mid summer onwards, although the odd variety may succumb badly before this, especially after a mild winter. Black spot spores can be air borne and are occasionally carried from one plant to another on the blades of secateurs. When they find a suitable leaf to settle on they will not be seen until small round-ish patches of black or dark brown appear. These will soon multiply. The areas not spotted will become yellow and eventually the leaf will fall. Fallen leaves should be collected and burnt, where possible, as the spores will over-winter in shallow soil where they will lay ready to begin their destruction the following year. In bad cases the spores will infect branches and unless tackled this is when the whole plant is at risk. Cut away what you can and apply a winter wash with a mild sterilant. There are now several available that will successfully deal with fungal diseases such a black spot. Some say that black spot can be deterred by spraying the plant with a solution of skimmed milk but I have never tried doing so.