powdery mildew

While in Maryland and Virginia recently our Extension Nursery Landscape and Turf Team of diagnosticians admired crepe myrtles (Lagerstroemia indica) in whites, reds, and lavenders.  Absolutely gorgeous trees for their flower displays and their attractive bark.

Like many powdery mildew diseases, high relative humidity but not high rainfall is a key to dogwood powdery mildew, caused by the fungus Erysiphe pulchra. There is a good bit of this disease this year in northeast Ohio, which is quite dry, and yesterday I took a look at some flowering dogwoods (Cornus florida) growing in pots in trials. There was a good bit of fungal mycelial growth and spores en masse evident on the foliage (what is called the “sign” of the pathogen), which is something everyone is familiar with for many powdery mildew diseases. Good examples are lilac...