Cause The fungus, Rhizoctonia spp., has been found on Astragalus in Oregon. Rhizoctonia spp. occurs in Oregon on other crops and may incite disease on numerous other crops including arugula, beets, snap bean, clover, peppermint, and brassicas. This fungus also causes damping-off of a wide range of plant species. It overwinters in soil as durable, long-lived structures known as sclerotia, but can also survive in association with infected plant debris. Rhizoctonia becomes active when soil temperatures are warm and may attack any part of the plant in contact with soil. The fungus is favored by poor soil structure and high soil moisture.
Symptoms Leaves turn yellow and then brown and dry as foliage dies. Plants wilt and may die. A brown rot of tissues may occur in the roots, taproot, crown portion, and lower stems.
Cultural control
- Avoid planting any crop that had Rhizoctonia rot problems.
- Practice a 3-year rotation with non-host crops (grains).