This month we touch on one of the diseases associated with roses. Philip was asked: What common problems do you encounter when growing roses and what advice would you give to prevent these issues? Do you have any experience with preventing and treating rose black spot?
I never experience problems with roses, but I am used to them issuing challenges to me. As with any living organism it may suffer an attack, fungi (blackspot, mildew and rust) are the most common adversaries.
Plants are no different to people, prevention is better than cure. Choose varieties with good disease resistance. We breed roses to have good blackspot resistance.
Secondly give them a good environment, are they well fed, watered, sunny and have enough space for decent airflow? A happy vigorous plant will have better natural resistance, just like us humans, stress leads to health issues.
Prevention is better than cure, sulphur can act as a preventative fungicide and be applied as a spray or drench in early season. If there is an attack of blackspot it usually starts after the first flush of flowers, when the plant has been expending lots of energy producing blooms.
There are proprietary products on sale to stop the spread of blackspot, to be used according to the manufacturer’s instructions. When deadheading it can be helpful to trim back harder, giving more of a Summer pruning which will encourage a larger amount of young vigorous growth which will be more resistant.
Black spot is unattractive on the plant and a severe attack year after year will weaken a plant. A lot of varieties marketed today can recover and grow back with vigour, so long as they have the basics needs of food, water and light provided in generous quantities. The first, second and third rules are to provide good growing conditions.
Look out for more of Philip’s expertise in next months blog!