Symptoms and Signs
Above ground symptoms on cilantro include stunting, yellowing, and wilting of foliage. Eventually, foliage turns brown and dry. The fungus causes a characteristic dry rot that is brown with deep fissures at or near the crown. The root and crown are partially or completely destroyed leading to plant death. On cilantro, Rhizoctonia diseases can be confused with Fusarium wilt; contact your local UCCE advisor or specialist for help with diagnosing.
Comments on the Disease
The fungus has many crop hosts and survives on plant debris in soil as small, resting structures called sclerotia that can survive for multiple years. This disease is most common during spring and summer when temperatures are between 77° to 92°F (25°– 33°C) and soils are moist. The fungus grows through the soil and infects the root and crown of plants. Rhizoctonia occurs in most soil types but is most severe in heavy, poorly drained soils where water collects. This fungus also causes damping off on a wide variety of crops.
Management
Cultural Control
To prevent disease development:
- Avoid planting into fields that have large amounts of undecomposed crop residue. Rhizoctonia colonies can thrive in organic matter.
- Avoid planting cilantro after a crop that had Rhizoctonia problems. Use non-host crops, like grains, in a three-year rotation to reduce pathogen levels.
Resistant cultivars are not available.
Organically Acceptable Methods
Use cultural controls in an organically certified crop.
Treatment Decisions
Pesticides are not effective against Rhizoctonia root and crown rot of cilantro and parsley.