Bean IPM

Legume ipmPIPE Diagnostic Series

Root Rots

Pythium, Rhizoctonia and Fusarium species


Figure 1 - Initial Pythium infection with sunken light tan tissue on hypocotyl and wilting.

Figure 2 - Initial Rhizoctonia root rot lesions are sunken, reddish brown and irregular shaped. Wilted plant is shown also.

Figure 3 - Initial Fusarium root rot lesions are reddishbrown and linear, while older lesions cover the roots and

Figure 4 - Fusarium wilt brown to orange discoloration of roots and hypocotyl. Discolored streaks extend upward in water conducting tissue (vascular bundles) to yellow, wilted leaves.


Factors favoring
  • Contaminated seed and/or infested debris from previous seasons
  • Low quality and/or old seed (more than 2 years after certification)
  • Cool, wet conditions after planting, and/or factors contributing to slow emergence
  • Soil compaction which reduces root growth, and crop rotation less than 3 years
  • Cool temperatures with daily highs less than 77ºF [25ºC] favor Rhizoctonia and Pythium before flowering, and greater temperatures after flowering favor symptom onset of Fusarium diseases
Roots that are rotted
Figure 1 - Pythium
Roots with spots
Figure 2 - Rhizoctonia
Lesions covering the roots
Figure 3 - Fusarium
Plant cut open to reveal discoloration in the vascular tissue
Figure 4 - Fusarium

H. F. Schwartz, Colorado State University, R. M. Harveson, University of Nebraska, and G. D. Franc, University of Wyoming

Photo credits

H. F. Schwartz, Colorado State University