Powdery Mildew Symptoms and Signs

DISEASE DIGEST

As noted already in BYGL 2012-05 http://bygl.osu.edu/content/powdery-mildew-diseases, powdery mildew fungi are already evident on many plants this spring, from roses to ninebark and from apples to crab apples.  Joe Boggs reports seeing DOGWOOD POWDERY MILDEW and MAGNOLIA POWDERY MILDEW in southwest Ohio.  He is seeing both the signs of the pathogen (the white fungal growth on leaves of these plants), and symptoms of damage due to these pathogens on leaves, namely desiccation of leaf tissue and reddening of the foliage.  Often these symptoms with certain powdery mildew diseases are misdiagnosed, as observers think of powdery mildew only in terms of the powdery-white growth which they see on leaves.  For example, powdery mildew of lilac typically does not exhibit much reddening and desiccation, and only the white powdery growth on the surface of the leaves.