What causes blackspot and powdery mildew?
Both are caused by spores that infect the leaves of the plants. The diseases spread from spores on the soil that gradually move up the plant. The spores move as water splashes on the soil. And, the spores grow and thrive under damp conditions. Prevention. • Cleanliness! Get rid of the source of the disease spores by cleaning up all leaves around your plants in the fall (throw them out, don t compost them!) • Watering. Water your roses so that the water doesn t splash up on the leaves. And, if you do have to use overhead watering, try to do it in early morning so that the leaves have a chance to dry out. • Air circulation. Try to plant your roses where there s lots of air circulation. Treatment • Lime sulphur in spring (before buds break typically in this area, mid-April). • Organic control of black spot on roses. “Brooklyn” mixture (see below) prevents the spread of blackspot and powdery mildew: it should be sprayed on your roses every week, starting as soon as the leaves open in the s
