This is a fungus that attacks stems, buds and leaves. It appears anytime during the growing season. It begins in early spring when shoots are approx. six inches tall. Young shoots discolour at base, wilt then fall over.
Leaf and Stem Spots
The cause of this could be from several fungal organisms, causing spots of varying sizes and colours. Organisms may affect stems, leaves, bud scales and flower petals. Peonies are affected when young and leaf and stem tissues are very succulent. Spots may be small reddish elongated areas that could enlarge to lesions with gray centres and reddish borders and could increase into zonate cankers. Cankers may cause twisting on stems, if stem is very young it may be killed.
This is a soil borne fungus (Verticillium albo-atrum). Peony shoots wilt, but basal parts look fine. Wilt is a destructive fungus and almost impossible to control because its in soil. If this is confirmed remove and destroy infected plant. Do not replant any plant in this area.
Also a soil fungus, this can cause stem rot. Parts or entire plant may wilt. Infected part of stem turns a light tan colour and may become dry and stringy. White mold (fluffy white)appears under humid conditions. Remove and dispose infected plant parts. (Do not drop any mold)
Peony Leaf Blotch
Also known as measles or stem spot. Optimal conditions for this is warm, humid weather. Leaf spots are glossy, purplish-brown on upper sides of leaves. Spots are chestnut brown on lower sides. Infection is more pronounced at margins of outer leaves, and as they continue to grow may become slightly distorted. Elongated reddish brown streaks will appear on young stems when fungal infection sets in. Infected tissue near crown may darken and depress as plant growth continues. Stems may show raised spots on upper half of plant. Leaf blotch may be managed by cutting stems at ground level in fall or early spring. Rake area before new shoots appear. Provide good air circulation and avoid wetting leaves when watering can help reduce disease.