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Viola Diseases

Name: Viola Diseases
SKU: ART-3396

Informational table showing disease name, symptoms, pathogen/cause, and management of Viola diseases.

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Updated:

November 27, 2023

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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, 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.