Powdery mildew, a fungal disease ... or apply an insecticidal soap. Lastly, as the Aster blooms begin to fade and the flowers start to brown naturally, consider deadheading the brown flowers.

Powdery Mildew (PM) is a fungal leaf disease caused by Blumeria graminis , which can reduce grain yield and quality in cereal crops. B. graminis species can be subdivided into Formae specialis groups ...