Red spot (Measles) of Peony

Peony plants infected with red spot (Cladosporium paeoniae)

Peony plants infected with red spot (Cladosporium paeoniae)

Close-up of leaf spots

Close-up of leaf spots

Red spot infected peony flower

Red spot infected peony flower

Pathogen: Cladosporium paeoniae

Hosts: Paeonia

Symptoms: Initial symptoms typically develop after bloom. Small reddish circular spots form on the foliage, lesions may coalesce making blotchy patches. The upper surfaces of infected leaves become a dark purple color, while the lower surface is brown. Foliage that is infected before it is fully expanded may become slightly distorted. Infection of stems causes reddish streaks.

Spread: This fungus survives on dead plant debris and in soil. Spores are spread by rain or wind.

Management: Remove and destroy infected plant material. Avoid overhead irrigation or carefully time irrigation such that the duration of leaf wetness is minimized.