Occurrence: Shaded areas during spring, summer, and early fall.
Distinctive disease growth on surface of the leaves of fine, gray-white, talcum powder usually on the upper surface of the leaves. The growth rapidly becomes dense and may cover the entire leaf. As colonization of the leaves by the pathogen increases, the leaf develops chlorotic lesions.
Conditions Favoring Disease Development: Poor air circulation, high atmospheric humidity but not visibly free water on the surfaces of the leaves, low light intensity, and an air temperature of 65°F.
Control: Management practices that improve air flow and reduced shading will aid in the reduction of the disease. Reducing length of time water sits on the leaf and ensuring proper watering practices are followed are critical in controlling the disease. Fungicides can be used to control ongoing growth of powdery mildew (follow label instructions particularly relating to timing, number of treatments, and rates).