Cause Pythium spp., Rhizoctonia solani, and Fusarium spp. Pythium is favored by cool, overly-wet soil conditions, Rhizoctonia by warmer soil temperatures, and Fusarium can grow at a wide range of conditions. All are soilborne and can produce long-living survival structures. Most soils that support plants have some level of microbial population that contain Fusarium spp. and commonly Pythium too. Rhizoctonia is not uncommon. But these microbes cause damping-off when seeds are germinating under unfavorable soil conditions or pathogens populations are at high levels. Typically problems are seen in western Oregon when seeds are sown in field soils when temperatures remain too cold, especially during rainy weather.
Symptoms Seeds either fail to emerge from soil or collapse soon after emergence, after a girdling canker develops at the soil line.
Cultural control
- Plant seed under optimal conditions for quick emergence and vigorous growth.
- Use sterile soil or potting mix to start seeds. Also disinfect any tools and equipment that might be used and contaminate the media.
- 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
- Apron XL at 0.085 to 0.64 fl oz/100 lb seed plus a dye for Pythium spp. See label for reentry restrictions.
- Allegiance-FL at 0.75 fl oz/100 lb seed plus a dye. Controls only Pythium spp. See label for reentry restrictions.
- Dynasty at 0.1 to 0.38 fl oz/100 lb seed plus a dye. 4-hr reentry.
- Maxim 4FS (Group 12) at 0.08 to 0.16 fl oz/100 lb seed for control of pathogenic Fusarium and Rhizoctonia spp. See label for reentry restrictions.
- Thiram 42-S or Thiram 480 DP at 5.2 fl oz/100 lb of seed for commercial application only (no home use). To control pathogenic Fusarium, Rhizoctonia, and other fungal spp. 24-hr reentry.
- Soil treatment.
- C-O-C-S WDG at 4 lb/100 gal water or at 2 oz/3 gal water. Can be re-applied on a minimum of 3-day intervals. Do not apply through any irrigation system. 48-hr reentry; 24-hr reentry for greenhouse applications.
- Quadris Flowable at 0.4 to 0.8 fl oz/1,000 row feet applied in a 7-inch or less band either in-furrow at planting or as a directed spray at cultivation. 4-hr reentry.
- Ridomil Gold SL may be banded or surface applied at 1 to 2 pints/A. To control Pythium only. Incorporate 2-inches deep when used. 48-hr reentry.
- Uniform at 0.34 fl oz/1,000 row feet applied in a 7-inch band in-furrow at planting. 0-hr reentry.
Biological control
- Bexfond at 7 to 14 fl oz/A for soil applications via drenches, in-furrow applications, drip irrigation, or sprays followed by irrigation. Reapply 3 to 4 weeks after planting. 4-hr reentry. O
- Bio-Tam 2.0 at 2.5 to 5 lb/A as a broadcast at sowing. See label for different methods and rates of application. 4-hr reentry. O
- Cease at 3 to 6 quarts in 100 gal water applied to soil at 1 pint/sq ft for each 3-inches of soil depth on 21- to 28-day intervals. For greenhouse plants only. 4-hr reentry. O
- Double Nickel LC at 0.5 to 4.5 pints/A for soil application on 14- to 28-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Mycostop at 0.07 oz/half lb seed at 0.05 to 0.08 oz/lb seed. 4-hr reentry. O
- Prestop WG as a soil drench or incorporation into growing medium. 4-hr reentry. O
- Rootshield WP at 3 to 5 oz/100 gal water for greenhouse soil drench and field chemigation or at 16 to 32 oz/A as an in-furrow spray. 4-hr reentry. O
- Taegro 2 at 2.6 to 5.2 oz/A on 7- to 14-day intervals can suppress soilborne diseases. 4-hr reentry. O
- Tenet WP at 2.5 to 5.0 lb/A at sowing will suppress certain fungal pathogens including Fusarium, Rhizoctonia, and Pythium spp. See label for specific application types and timings. 4-hr reentry. O