Sorghum downy mildew


Several species of the genera Peronosclerospora, Sclerospora, and Sclerophthora are responsible for downy mildews:

  • Crazy top downy mildew - Sclerophthora macrospora
  • Brown stripe downy mildew - Sclerophthora rayssiae var. zeae
  • Green ear disease- Sclerospora graminicola
  • Java downy mildew - Peronosclerospora maydis
  • Philippine downy mildew- Peronosclerospora philippinensis
  • Sugarcane downy mildew- Peronosclerospora sacchari
  • Sorghum downy mildew- Peronosclerospora sorghi

Nature of damage

  • Some species causing downy mildew also induce tassel malformations, blocking pollen production and ear formation.

Signs

  • Symptom expression is greatly affected by plant age, pathogen species, and environment. Usually, there is chlorotic striping or partial symptoms in leaves and leaf sheaths, along with dwarfing.
  • Downy mildew becomes conspicuous after development of a downy growth on or under leaf surfaces.
  • Leaves may be narrow, thick, and abnormally erect.

Factors favoring development

  • The diseases are most prevalent in warm, humid regions.
  • Cultivation of alternate hosts in rotation or simultaneously will build pathogen pressure.
  • Moist soils favor oospore germination and therefore damp soil as a result of irrigation or reduced tillage techniques will encourage disease development.

Geographic development

  • These diseases are of serious concern to maize producers in several countries of Asia, Africa, and throughout the Americas.

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