Powdery Mildew is a generic term for the unsightly disease that grows on the surface of many plants. There are over 1600 different species of fungus that will cause Powdery Mildew symptoms and they are usually host specific, eg. infected Phlox will not likely spread its disease to adjacent Forsythia. That is not so say that both plants won’t be showing symptoms (if the conditions are favorable it is likely that they will), just that the causal organisms will be different.

Warm days and cool nights with significant dew fall in mid to late summer are prime conditions for the growth of PM. Ensuring good air circulation and dry foliage overnight (i.e. morning irrigation not evening) are paramount cultural techniques for avoidance. Excellent sanitation is also a requirement. The fungal spores over-winter in the scales of dormant buds as well as any discarded foliage.

Growing of resistant cultivars will also decrease frustrations.