Pythium root rot of wheat

Pythium root rot is a soil-borne disease that reduces yield in wheat growing regions throughout the U.S. and Canada. It is caused by Pythium spp. and Globisporangium spp. Symptoms include stunting, yellowing, tiller reduction, and poor stand. Symptoms are generally more noticeable in low lying areas. Infected roots are shorter, have few root hairs, and are necrotic. The outer layer of the root (the cortex) falls off easily. Symptoms can be observed from seedling stage to ripening.

The outer layer of the root (the cortex) of Pythium-infected plants falls off easily. Image: M. Burrows.
Outer layer of root tissue missing on plant with Pythium root rot. Image: M. Burrows. 

Cool, wet, poorly-drained soils favor Pythium root rot. Fields that retain moisture, such as those with heavy soils or crop residue on the surface, will be at greater risk for disease development.

Disease risk can be reduced by selecting a planting date that avoids cool, wet soil. Residue management allows soil to warm and dry more quickly in spring. Fungicide seed treatments are labeled for Pythium, but effectiveness is limited to the first few weeks after planting.

Gallery

Gallery image: M. Burrows.