|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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