Pythium Seed Rot & Damping-Off

Pythium can rot seeds and seedlings prior to emergence and can cause postemergence damping-off under wet conditions. The characteristic symptom of most Pythium infections is soft, brownish-colored rotting tissue. In established plants, secondary roots can be soft and rotted, and roots and plants may be stunted or killed in some cases.Phytophthora is a related pathogen that causes similar symptoms; the two can be differentiated only through laboratory examination.
Background Information
  • Pythium is a common and widespread pathogen. This pathogen primarily affects seedlings and can cause extensive thinning of stands, but it can also cause root rot and poor growth in older plants. It is most damaging in wet and slowly drained soils.
Disease Agent
  • Pythium is a soilborne, fungal-like pathogen. Several different species of this pathogen damage soybean. The various species of Phythium that infect soybean have a wide host range that can include corn and other crops.
Symptoms
  • Phytium can rot seeds and seedlings prior to emergence and can cause postemergence damping-off under wet conditions.
  • The characteristic symptom of most Pythium infections is soft, brownish-colored rotting tissue.
  • In established plants, secondary roots can be soft and rotted, and roots and plants may be stunted or killed in some cases.
  • Phytophthora is a related pathogen that causes similar symptoms; the two can be differentiated only through laboratory examination.
Time of Occurence
  • Primarily spring and early summer, although infection can also occur later in the season.
Conditions Favoring Disease
  • Wet and cool conditions
  • Low, poorly drained areas
  • Compacted and clay soils
  • Herbicide damage
Disease Managment
    • Use seed treatments.
  • Some seed treatments can reduce seed and seedling rot.
    • Improve soil drainage.
  • Avoid low areas of fields, especially if a field has a history of seedling or root rot problems.
  • Plant in soils warmer than 55°F.
  • Resistant varieties are not available.