I was very disappointed with the Roses this year as all but two were blighted with Black Spot. I was aware of this fungal disease and have removed infected leaves as I saw them but I didn’t use any spray at all. Some of my bare root roses didn’t flourish at all and I put this down to the very cold wet winter. I also decided that I had made a mistake by mixing spring bulbs in the pots with the roses. Death by Tulip. I intend to try and tackle the problem early next year.
Rose Blackspot is best prevented with an anti fungal spray early in the season before the foliage starts to show through. To be extra cautious spray the ground around the bush too. Most garden roses are prone to this disease and much depends on cleanliness for successful control. With roses that are susceptible to blackspot spraying every two weeks may be necessary. Hard pruning in the spring and burning all pruning material is best with any rose plant that regularly get blackspot. A feed with a high potash content will also help to allay the disease. This should be carried out early in spring in order that the rose plant may take the potash in as a preventative.
Make your own anti fungal spray with baking powder and washing up liquid mixed with water and put into a spray bottle. Spray both sides of leaves. Add one box of baking powder to water and add baby shampoo. Mix well before spraying. Spray every two weeks. This mixture changes the ph to kill and prevent fungal growth. Shampoo acts as a coating agent to maintain alkaline ph. Respray after rain.