Peony Leaf Blotch

Encyclopedia Article

Overview of peony leaf blotch 

Peony leaf blotch is also known as measles or stem spot. Warm, humid weather provides optimal conditions for infection by the causal fungus, Cladosporium paeoniae.

Image of a peony flower with a case of leaf blotch
Leaf blotch symptoms

Signs and symptoms of peony leaf blotch

The leaf spots are glossy and purplish-brown on the upper sides of leaves. On the lower sides, spots are chestnut-brown. Infection is generally more pronounced at the margins of outer leaves. Leaves may become slightly distorted as they continue growing.

Disease cycle of peony leaf blotch

Fungal infections on young stems first appear as elongated, reddish-brown streaks. As plant growth continues, infected tissue near the crown may darken and become depressed. Stems on the upper portion of the plant may show individual, raised spots.

Type of Sample Needed for Diagnosis and Confirmation

The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if you plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each states diagnostic laboratory for U.S. residents.  If your sample is from outside of Iowa please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us

Image of a peony with leaf blotch symptoms
Peony flower with a case of leaf blotch

Management of peony leaf blotch   

To manage peony leaf blotch, cut the stems at ground level in the fall or early spring. Rake the area before new shoots appear. Fungicides are available to help control the disease, but must be used in combination with other management practices. Also, providing good air circulation and avoiding wetting the leaves when watering can help reduce disease severity.

 

 

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