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GrainGenes Pathology Report: Downy Mildew

Downy Mildew
Other Name
Crazy Top
Host Species
Triticum aestivum
Hordeum vulgare
Avena sativa
Causal Organism
Sclerophthora macrospora
Scleropthora macrospora
Sclerospora philippiniensis
Pathogen is a 'water mold' fungus requiring saturated soil conditions for infection to occur. Diseased plants are most often noticed along or in standing water. Infected seedlings appear stunted, chlorotic, tiller profusely and have thickened, leathery leaves. Severely infected plants usually die before jointing. Infected survivors exhibit twisted heads and leaves. Contrary to the name, 'downy' fungal growth is seldom visible on wheat. Barley, corn, sorghum, oats and 100+ species of perennial and annual grasses serve as alternate hosts.
Symptoms typical of...Sclerophthora macrospora.
Downy mildew developing on spring wheat...
Wheat plants with downy mildew...
Triticale infected by Sclerophthora macrospora...
Oospores of Sclerophthora macrospora...
ReferenceKephart KD (1993) Winter wheat disease management Insect and plant disease management handbook.
ReferenceHarder DE and Haber S (1992) Oat diseases and pathologic techniques Oat Science and Technology 307-425.
Reference(1987) Compendium of wheat diseases.