- Myrothecium crown rot (Myrothecium roridum): Plants yellow and collapse, often after transplanting.
- Phytophthora crown rot (Phytophthora parasitica): Softening and discoloration of stem base leads to browning of lower leaf bases and plant collapse.
- Thielaviopsis root rot (Thielaviopsis basicola): Scattered individual plants in plug tray or packs are stunted and yellowed; roots are stunted and may be blackened.
- Cercospora leaf spot (Cercospora violae): Leaf spots begin as small purple spots and enlarge to form large 1/4 in. diameter dark spots without a sharp circular outline (usually seen on lowest leaves). Rogue out immediately.
- Downy mildew (Pernospora violae): Pale areas of leaves, with sporulation on leaf undersurface.