General Information

Pythium species are oomycetes (fungi-like organisms) that can infect soybean seed within hours after planting causing seed rot and is also associated with death of a developing seedling (called ‘damping-off’) and death of a seedling prior to emergence (called ‘pre-emergence damping-off’) – all resulting in the absence of plants in the row. Infection is favored by wet conditions after planting and is typically a problem in cool soils in north central U.S. and Canada. Symptoms include rotten, mushy seeds and/or seedlings with poorly developed roots. Water-soaked lesions may be present on the hypocotyl or cotyledons.

  • Plant high-quality seeds in warm, well-drained soil. Planting on beds and/or avoiding deep planting may improve stands and prevent saturated soil from surrounding the seed
  • Use cultivation practices that prevent or reduce soil compaction and promote good soil drainage
  • Seed treatments – seed treatments containing Metalaxyl or Mefenoxam best target oomycetes, although sensitivity may differ among species and adding a broad-spectrum fungicide seed treatment may improve control of Pythium Links to Seed Treatment Fungicide Efficacy Table – mobile version or pdf

Pythium seedling blight

Pythium seedling blight 2
Pythium seedling blight (oomycete: Pythium species)