Pythium Root Rot

P. arrhenomanes (Drechs).
P. graminicola (Subr).
P. ultimum (Trow).
P. aristosporum (Vanderpool).
P. irregulare (Buisman).

  1. Symptoms: The fungus causes generalized stunting that is often difficult to recognize without comparison to a disease-free control (picture at left). The fungus also causes a reduction in total root length, killing root tips and lateral roots, rendering the roots unable to expand through the soil (picture at right). Pythium also destroys root hairs, preventing the uptake of necessary water and nutrients. In young seedlings, signs of nutrient deficiencies such as chlorosis, or purpling of the leaves, can be seen.
  2. Development: The most severe damage caused by Pythium is typically associated with cool, wet soils, especially those which are poorly drained. It is seen most commonly in low spots in the field, or where excess crop residues slow the drying and draining of soils in the spring.
  3. Hosts/Distribution: Pythium is ubiquitous through most soils, and have a wide host range, attacking a variety of other rotation crops and weeds.
  4. Importance: Pythium causes above-ground stunting, reduction in biomass, and reductions in yield, and is ubiquitous through most soils.

Pythium Root Rot Pythium Root Rot


  • Dr. Timothy C. Paulitz- Leader Soil Pathology Research, Washington State University, Washington, United States of America.