Once the pathogen has invaded the midrib or veins, it can advance rapidly to the petiole and stem, which results in the collapse of the whole leaf. Lesions expand rapidly. This results in a moldy gray appearance and rapid disease spread. Infection by botrytis blight causes collapse of the periole. Botrytis blight lesions move up the petioles and into the leaves.
Longitudinal lesions appear on the stems.
Spores of Botrytis are unicellular, smooth-walled and roughly oval in shape. Under dry conditions, the disease develops slowly and forms small to large, brown or black lesions or even becomes quiescent. Large lesions often split leaves or form holes in the center. Round, spherical or irregular microsclerotia may be produced on dead or dying plant parts. Although B. cinerea does not usually kill coneflower plants, it often heavily infects disc flowers and young shoots.