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Viola Diseases

Informational table showing disease name, symptoms, pathogen/cause, and management of Viola diseases.
Diseases Symptoms Pathogen/Cause Management
Aster yellows Leaves are yellowed and narrow rather than oval. An abnormally high number of shoots form. Phytoplasma Remove infected plants. Control leafhoppers.
Bacterial infection An abnormally high number of shoots form. Rhodococcus fascians Remove infected plants.
Black root rot Plants are yellowed, stunted and die. Thielaviopsis basicola Try to maintain the soil pH below 6.2 where the violets are growing. Provide good soil drainage. Apply a fungicide to protect plants.
Crown rot Dying plants have white fungal growth on stems at the soil line. Small, golden-tan, mustard-seed sized structures dot the white growth. Sclerotium rolfsii Remove infected plants. Keep mulch away from the base of the plants.
Downy mildew Leaves have purplish or yellowed areas. Peronospora or Bremiella Apply a fungicide to protect plants in the spring when cool, wet weather prevails.
Fungal leaf spots Small spots, on generally on lower leaves, enlarge and become dark purple to black, 1/4” or more in diameter with feathery margins. Leaves then yellow. Cercospora, Alternaria, Ascochyta, Botrytis, Centrospora, Ciborinia, Colletotrichum, Cryptostictis, Cylindrosporium, Heterosporium, Marssonina, Phyllosticta, Ramularia, Septoria When irrigating, keep water off the foliage. Apply a fungicide to protect plants.
Powdery mildew White fungal growth develops on the upper surface of leaves. Sphaerotheca Apply a fungicide to protect plants as soon as any white fungal growth is observed.
Pythium root rot Plants wilt and die as lower stems and roots discolor and die. Pythium Remove infected plants. Apply a fungicide to protect plants.
Rhizoctonia stem rot Roots and stems brown as plants wilt and die. Rhizoctonia Remove infected plants.Apply a fungicide to protect plants.
Rust Pustules yellow-orange spores form on the underside of leaves. The upper side of the spot is yellow. Puccinia or Uromyces Avoid overhead irrigation. Apply a fungicide to protect plants.
Scab White spots with purple edges form slightly swollen areas along petioles and leaf veins. Sphaceloma violae Apply a fungicide to protect plants.

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Viola Diseases

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