Common root rot
Cochliobolus sativus (Ito & Kuribayashi) Drechs. Ex Dast. [teleomorph]
Bipolaris sorokiniana (Sacc.) Shoemaker
Crown rot (foot rot, seedling blight, dryland root rot)
Fusarium spp.
F. pseudograminearum O’Donnell et. T. Aoki sp. nov.
Gibberella zeae (Schwein.) Petch [teleomorph]
F. graminearum Schwabe, Group II [anamorph]
G. avenacea R.J. Cook [teleomorph]
F. avenaceum (Fr.:Fr.) Sacc. [anamorph]
F. culmorum (W.G. Smith) Sacc.
- Symptoms: These fungi produce a darkening or browning of the root, crown, and basal culm tissues. Individual plants or groups of plants may lodge. White spikes often are visible just prior to normal physiological maturity (picture at left). lnfection early in the crop development can cause pre- or postemergence "damping off" of seedlings (picture at right). Since each fungus can attack a different plant part at a different growth stage, positive field identification of the causal agent is difficult.
- Development: The roots or crown tissues are infected by conidia or mycelia present on crop debris, Infection by and development of common root rot is favored by warm, dry soils when the plants are under stress. The root, foot, and crown rots caused by Fusarium spp. are generally favored by cooler, moist soils.
- Hosts/Distribution: These diseases affect all major small grain cereals grown in the temperate regions of the world.
- Importance: Major epidemics have not been reported. However, localized losses can result from thinned stands, a decrease in the number of tillers, and from reductions in head size and test weights.
