Downy Mildew

Also known as Crazy top
Sclerophthora macrospora (Sacc.) Thirumalachar et al.

  1. Symptoms: Diseased plants tiller profusely; they have short, erect, irregular, or crooked yellowish green culms; and the leaves are thick, erect, and usually in whorls (picture on left). Tillers die prematurely or spikes never develop. If formed, the spikes may be branched, and some of the floral tissues grow into leaflike structures (picture on right).
  2. Development: The disease in cereals is generally associated with water-logged or excessively irrigated fields. Development is enhanced if temperatures range between 10 and 25ºC. Infection may be initiated by inoculum in the soil, or from diseased weed hosts, and water must be present for infection to occur. Symptoms are most obvious during the tillering/stem elongation growth stages of the host plant.
  3. Hosts/Distribution: The fungus has a broad host range, including small grain cereals, maize, sorghum, and most grasses. It may be found wherever soils become water-logged or are poorly drained.
  4. Importance: Small, localized epidemics can occur when conditions are favorable. There have been no reports of widespread and destructive epidemics.

Downy Mildew Downy Mildew