Cause The fungus, Rhizoctonia solani, which can survive in soil for at least several years. The fungus has a broad host range and can be spread by movement of infected plant debris. Disease is favored by warmer soil temperatures.
Symptoms A dry brown rot can develop on roots and a reddish brown rot of the lower portion of the main stem may develop. Leaf infections are characterized by areas of dry brown tissue and buds; medical marijuana plants grown in Oregon have been infected.
Cultural control
- Rotate out of susceptible hosts, preferably for 3 years.
- Avoid over-irrigating early in the season. Cooling soil with irrigation slows emergence and favors the fungus.