Cause Rhizoctonia solani, a soilborne fungus. It survives in the soil as sclerotia or as mycelium colonizing bits of organic matter. Roots become infected as they grow past these structures. The fungus then grows along root surface, forms an aggregation called an infection cushion, pushes into the root where it colonies, spreads and kills the tissue. The fungus can form knots of mycelium that develop into sclerotia. These are released into the soil as the plant debris decomposes.
Symptoms Rotted roots at and below the soil line even in well-drained planting media.
Cultural control
- Start with healthy plants.
- Use sterilized planting media.
- Do not overwater after transplanting.
- Check electrolyte concentration (EC) levels regularly.
- Use low ammonium-nitrogen.
Chemical control Apply to plugs before transplanting.
- Medallion WDG at 1 to 2 oz/100 gal water. Using with oils or adjuvants may damage plant. Group 12 fungicide. 12-hr reentry.
- Terraclor 400 at 6 to 12 fl oz/100 gal water. Application rate of this solution is based on pot diameter and/or depth of soil, see label for details. Group 14 fungicide. 12-hr reentry.
- Terraguard SC at 4 to 8 fl oz/100 gal water. Group 3 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.