|Bacterial blight||Spotting may be accompanied by rings of dark red pigment or sometimes yellow haloes.||Xanthomonas||Maintain good air circulation. Promptly remove and destroy plant debris at season end. Avoid overhead irrigation.|
|Botrytis blight||Young shoots discolor, wilt, and fall over. Later, browned buds and blighted leaves may develop masses of gray, fuzzy fungal spores.||Botrytis cinerea or Botrytis paeoniae||Avoid overhead irrigation. Maintain low humidity. Remove infected plant parts. Clean up debris at season end. Apply a fungicide to protect plants.|
|Crown gall||Galls or overgrowth of tissue form at the soil line or along the stems||Agrobacterium tumefaciens||Remove infected plants and surrounding soil. Avoid wounding plants at or near the soil line.|
|Leaf blotch or measles||Small, reddish spots that can coalesce to form large, irregular purple blotches on leaves and stems. Lesions are also formed on stems.||Cladosporium paeoniae||Avoid overhead irrigation. Maintain low humidity. Remove infected plant parts. Clean up debris at season end. Apply a fungicide to protect plants.|
|Nematodes||Plants are stunted and yellowed. Small galls occur on roots or roots have little branching||Meloidogyne, Rotylenchus, Ditylenchus||Remove infected plants and do not replant there for one year. Till the soil to keep it weed free for one year before replanting.|
|Phytophthora blight||Infected parts become dark brown to black and somewhat leathery, and shoots may die. Crowns may also develop a dark, wet rot.||Phytophthora||Avoid planting in wet or poorly drained areas. Remove and destroy infected plants.|
|Powdery mildew||Foliage becomes coated with white mycelium.||Erysiphe||When mildew is observed, apply a fungicide to protect plants.|
|Root rot||Plants are stunted, yellowed, wilt, and die.||Fusarium, Rhizoctonia, or Thielaviopsis||Remove infected plants.|
|Southern blight||Stems turn water-soaked at the base, then wilt. The base of diseased stems will often show fans of thick, ropy-textured fungal mycelium and numerous, tiny, spherical sclerotia that turn from white to brick red as they mature.||Sclerotium rolfsii||Destroy infected plants.|
|Verticillium wilt||Wilting of shoots in the absence of damage to the crown.||Verticillium albo-atrum, V. dahliae||Remove and destroy infected plants, and do not replant peonies.|
|Viruses,||Ringspots, light and dark green mottling on the leaves, stunting, curled leaves, and poor growth.||Tobacco rattle, Tomato spotted wilt, Alfalfa mosaic viruses||No treatment is recommended if plants are only mottle but are growing well. Stunted plants and those not growing well should be removed.|
|White mold||Can cause stem rot on peony. The entire plant may wilt, or only a portion of it. Infected areas of the stem turn a light tan color and may become withered and stringy. Under wet conditions, fluffy white fungal growth (mycelium) often appears.||Sclerotinia sclerotiorum||Do not replant in infested areas. Maintain good air circulation.|
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