Black spot is a common problem on roses but can be found on other plants too. The spots can be of various colours - grey, brown or black. The spots are in fact dead leaf tissue caused by the fungus which spreads the disease. Spots can sometimes join together to form larger areas of dead tissue. Some Roses also develop smaller black spots on stems.
There are few other symptoms than the spots themselves. However, diseased plants frequently have other problems causing weaknesses which enable the fungal disease to develop. It is worthwhile carefully checking any plant with leaf spot.
Treatment and control
General tips: Immediately remove and destroy all infected leaves and plant parts. Pick up any fallen foliage and destroy. To reduce the chances of re-infection for the following season, prune shrubs back hard. Where roses were infected with black spot disease in the previous season, then start spraying with a suitable fungicide as new leaves open and repeat at fortnightly intervals.
Spray with suitable fungicides: For Roses and other ornamental plants, products with one of the following active ingredients will enable control although directions should be checked to ensure suitability for specific plants: FungusClear Ultra and FungusClear 2 Gun! Continue spraying at fortnightly intervals throughout the season.