Viola Diseases

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

Updated: August 8, 2017

Viola Diseases
DiseasesSymptomsPathogen/CauseManagement
Aster yellowsLeaves are yellowed and narrow rather than oval. An abnormally high number of shoots form.PhytoplasmaRemove infected plants. Control leafhoppers.
Bacterial infectionAn abnormally high number of shoots form.Rhodococcus fasciansRemove infected plants.
Black root rotPlants are yellowed, stunted and die.Thielaviopsis basicolaTry to maintain the soil pH below 6.2 where the violets are growing. Provide good soil drainage. Apply a fungicide to protect plants.
Crown rotDying plants have white fungal growth on stems at the soil line. Small, golden-tan, mustard-seed sized structures dot the white growth.Sclerotium rolfsiiRemove infected plants. Keep mulch away from the base of the plants.
Downy mildewLeaves have purplish or yellowed areas.Peronospora or BremiellaApply a fungicide to protect plants in the spring when cool, wet weather prevails.
Fungal leaf spotsSmall 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, SeptoriaWhen irrigating, keep water off the foliage. Apply a fungicide to protect plants.
Powdery mildewWhite fungal growth develops on the upper surface of leaves.SphaerothecaApply a fungicide to protect plants as soon as any white fungal growth is observed.
Pythium root rotPlants wilt and die as lower stems and roots discolor and die.PythiumRemove infected plants. Apply a fungicide to protect plants.
Rhizoctonia stem rotRoots and stems brown as plants wilt and die.RhizoctoniaRemove infected plants.Apply a fungicide to protect plants.
RustPustules yellow-orange spores form on the underside of leaves. The upper side of the spot is yellow.Puccinia or UromycesAvoid overhead irrigation. Apply a fungicide to protect plants.
ScabWhite spots with purple edges form slightly swollen areas along petioles and leaf veins.Sphaceloma violaeApply a fungicide to protect plants.