Today 
Aptly named blackspot is a fungus that causes dark spotting on rose leaves and stems. Eventually, leaves turn yellow and drop off before autumn. Spores overwinter on the fallen leaves and re-infect the plant in spring when new foliage appears. Plants can be weakened by recurrent attacks, especially if they occur early in the season.
Solution
Organic
Pick up and destroy fallen leaves. When pruning, cut out any stems with blackspot on. In late-winter, spread a thick layer of mulch around the base of the affected plant to prevent rain splashing soil-borne spores on to new spring growth. Grow rose varieties that are resistant to blackspot - these are suggested in the catalogues of specialist rose growers.
Chemical
Spray against blackspot with fungicide containing penconazole. Follow the instructions, treating the new foliage in early spring, with further sprayings at regular intervals through the season.
