Cause Both Pythium spp. and Rhizoctonia solani can cause pre- and post-emergence damping-off. Neither has been reported in the Pacific Northwest but Pythium damping-off has been found by the OSU Plant Clinic. Pythium is favored by cool and overly moist soil conditions.
Different Alyssum spp. were equally susceptible to Pythium spp. in the absence of nickel. However, nickel hyperaccumulating Alyssum species survived better as soil nickel concentrations increased.
Symptoms Stems of seedlings or recent transplants collapse at the soil line and die. Pythium is also reported to cause a basal stem rot.
Cultural control
- Plant in pasteurized, well-drained raised beds or soilless media. Also disinfect any tools and equipment that might be used and contaminate the media.
- Avoid planting seed at too high a density.
- Rotate to different beds from year to year.
- Avoid reusing pots or trays from a previous crop for propagation. If pots must be reused then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min.
Chemical control for Pythium
Rotate fungicides from different groups that have a different mode of action for resistance management.
- Banol at 2 to 3 fl oz/10 gal water. Group 28 fungicide. 12-hr reentry.
- Mefenoxam 2 AQ can be used if not phytotoxic at 0.12 to 0.24 fl oz/100 gal water as a soil drench, at 0.49 to 0.98 oz/100 gal water at transplanting, and see label for media incorporation. Group 4 fungicide. No restrictions on reentry when used as a soil drench or media incorporation.
- Proplant at 2 to 3 fl oz/10 gal water. Group 28 fungicide. 12-hr reentry.
- Subdue MAXX at 0.5 to 1 fl oz/100 gal water can be used if not phytotoxic. Group 4 fungicide. 12-hr reentry. No restrictions on reentry when used as a soil drench.
- Terrazole 35 WP at 3.5 to 10 oz/100 gal water as a soil drench. Group 14 fungicide. 12-hr reentry.
Chemical control for Rhizoctonia
- Chipco 26019 FLO at 13 fl oz/100 gal water. Use 1 to 2 pints of this solution per sq ft. Group 2 fungicide. 12-hr reentry.
- Medallion WDG at 1 to 2 oz/100 gal water. Use with oils or adjuvants may cause plant damage. Group 12 fungicide. 12-hr reentry.
- Spirato GHN at 1 to 2 fl oz/100 gal water. Use with oils or adjuvants may cause plant damage. Group 12 fungicide. 12-hr reentry.
Reference Ghaderian, Y.S.M., Lyon, A.J.E., and Baker, A.J.M. 2000. Seedling mortality of metal hyperaccumulator plants resulting from damping off by Pythium spp. New Phytol 146:219-224.