Scab (Head Blight)

Fusarium spp.
Gibberella zeae (Schwein.) Petch [teleomorph]
Fusarium graminearum Schwabe, Group II [anamorph]
G. avenacea R.J. Cook [teleomorph]
F. avenaceum (Fr.:Fr.) Sacc. [anamorph]
F. culmorum (Wm. G. Sm.) Sacc.
Monographella nivale (Schaffnit) E. Müller [teleomorph]
Microdochium nivale (Fr.) Samuels & I.C. Hallett [anamorph]

  1. Symptoms: Infected florets (especially the outer glumes) become slightly darkened and oily in appearance (picture at left). Conidiospores are produced in sporodochia, which gives the spike a bright pinkish color (picture on right). Infected kernels may be permeated with mycelia and the surface of the florets totally covered by white, matted mycelia.
  2. Development: Several species of Fusarium can attack the spikes of small grain cereals; the ovaries are infected at anthesis, and infection is favored by warm and humid weather during and after heading. Temperatures between 10 and 28ºC are required for infection. Once primary infection has occurred, the disease can spread from floret to floret by mycelial growth through the spike structure.
  3. Hosts/Distribution: All small grain cereals may be affected by this disease. Fusarium spp. are present in nearly all soils and crop residues.
  4. Importance: Severe levels of infection can cause yield losses of more than 50% and significant reductions in grain quality. Kernels from diseased spikes are often shriveled. Harvested grain containing more than 5% infected kernels can contain enough toxin to be harmful to humans and animals.

Scab Scab

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