Powdery mildew is a common fungal disease which affects leaves, flowers and tender stems. The source of the infection could be any one of several different fungal strains. Powdery mildew occurs in both dry and humid weather, with the most severe cases generally being on plants in shady areas.
The off-white substance which coats the tender vegetation is made up of fungal spores and strands. The fungus drains the nutrients from the leaves, causing the leaves or blossoms to become discolored, often resulting in the death of the affected parts.
Powdery mildew is spread by airborne spores. Since each strain of fungus may infect a variety of plants, in infestation could spread rapidly through a landscape or garden.
Powdery mildew can be treated with a fungicide appropriate for the infected plant. If trees are in proximity to the infected plant, a professional arborist should be consluted to determine if powdery mildew has invaded the trees.