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Infection by Pythium

Pythium Root Rot

Pest Background

  • Caused by many species of the oomycete pathogen Pythium.
  • Pythiumspecies are favored by periods of extended soil wetness.
  • Pythiumspecies differ in optimal temperatures for growth and can have varying responses to fungicides.
  • To date, over 15 species have been identified in the Mid-Atlantic region, withPythium graminicolabeing most common.

 

Identification

  • Symptoms of Pythium Root Rot can include stunted, slower growing plants, to severely infected, dead plants that die after emergence (Fig 2).
  • Infected plants typically have brown, rotted roots and mesocotyl (Fig 1and 3).
  • Stand reduction is typically seen in low-lying, wet regions of the field.
  • Plants that are infected early generally maintain reduced root systems throughout the season, with poorly formed ears.
Comparison of corn hypocotyls healthy vs infected
Fig 1: Comparison of corn hypocotyls healthy (left) vs infected (right)
Fig 2: Aboveground symptoms of infection by Pythium
Fig 2: Aboveground symptoms of infection by Pythium (right)
Developing corn root system infected by Pythium
Fig 3 : Developing corn root system infected by Pythium

Management

 

  • Seed treatments with activity against oomycetes can provide protection for approximately 14 -21 days.
  • Limit water usage early in the season to avoid saturated field conditions.

 

References

Bickel, J. T., & Koehler, A. M. (2021). Review of pythium species causing damping-off in corn.Plant Health Progress,22(3), 219-225. doi:10.1094/PHP-02-21-0046-FI

 

 

Authors: Madeline Henrickson and Dr. Alyssa Koehler


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