Cause The soilborne fungi or fungus-like microorganisms, Fusarium spp., Pythium spp. and Rhizoctonia solani, may attack before, during, and after germination. In the Pacific Northwest, Pythium spp. are the major cause of pre- and post-emergence damping-off of young clover seedlings. Pythium is favored by cool, wet soils. Rhizoctonia solani is more often associated with post-emergence damping-off of older seedlings and soil temperatures are warm; it is favored by warmer soil temperatures. These fungi can survive several years in soil and can infect other plant species including beans and other vegetable crops. Red clover becomes more resistant to these soilborne pathogens after plants reach the 4- or 5-leaf stage.
Symptoms Seeds either do not emerge, or emerged seedlings often develop blackened stems and wilt. Very few infected seedlings survive and root die-back maybe evident.
Cultural control
- Encourage rapid emergence by managing planting depth (shallow), timing, and soil moisture. Work soil at moisture conditions that reduce soil compaction.
- Avoid planting in wet or poorly-drained soil.
- Rotate clover crops with grass and grain.
- Use good quality seed.
- Lime acid soils to get a pH of 6.5 or 7.0.
- If the stand is lost, replant ideally in dry, warm weather, which is more favorable for germination.
Chemical control
- Treat seed with fungicides.
- Acquire at 0.75 to 1.5 fl oz/100 lb seed plus a dye. For control of Pythium only. See label for reentry restrictions.
- Allegiance-FL at 0.75 to 1.5 fl oz/100 lb seed when Pythium is a problem. See label for reentry restrictions.
- Apron XL at 0.64 fl oz/100 lb seed when Pythium is a problem. See label for reentry restrictions.
- Captan 4L at 8 fl oz/100 lb seed.
- Maxim 4FS at 0.08 to 0.16 fl oz/100 lb seed. For control of pathogenic Fusarium and Rhizoctonia spp. See label for reentry restrictions.