The disease is present on hybrid teas and florabundas by June, but it flourishes best on these types in the late summer as the nights become cool. The fungus overwinters in the buds or on the canes and the first symptoms of the disease are slight curling of the leaves followed by the appearance of white powdery growth. Buds may not open at all, or if they do open, the flowers are misshapen. The leaves sometimes become blistered and have a reddish cast under the white fungus growth. This reddish case may become almost black in appearance.
Powdery mildew is prevalent on succulent growth brought about by excessive nitrogen application.