Gray mold blight attacks peony

Botrytis paeoniae attacks peony young stems, leaves and buds. Leanne Pundt at Univ. of Conn. said the fungal disease causes a brownish-black rot covered with gray mold. Rot may extend several inches below the bud.
Newly emerging shoots develop a blackened, blighted appearance. Half open flowers turn brown in part or entirely. The fungus usually fruits readily on infected parts.
Prompt removal of infected plant parts lowers the possibility of new infections. Good sanitation includes cutting and burning all old stalks in the fall and removal of mulch early in spring. Sometimes removal of the top 2 inches of soil, replacing with new soil, is helpful in stubborn cases.
Control can also be achieved with the use of fungicides applied when new growth is emerging or as soon as symptoms are visible. Compounds registered for use include mancozeb and thiophanate-methyl.