Common root and foot rot of wheat
Common root and foot rot occurs in all wheat production areas of the U.S. and Canada. The pathogen (Bipolaris sorokiniana) has a wide host range and also causes a foliar disease known as spot blotch. Symptoms include dark, chocolate brown to black lesions on the coleoptile, stem, roots, and/or subcrown internode (the area above the seed to the soil line). Heavily diseased roots result in stunting and poor tiller and root development. Early season infections can result in poor stand. Premature ripening may occur resulting in shrunken kernels and, in some cases, sterile spikes. Spot blotch symptoms first appear on lower leaves and progress upwards as conditions permit. Lesions are oblong and brown with a dark brown center. Symptoms can be observed from tillering stages through ripening. Common root and foot rot on wheat plants. Image: M. Burrows
Microscopic view of fungal reproductive structures of Bipolaris sorokiniana, the pathogen that causes common root and foot rot. Image: M. Burrows
In general, stressed areas of a field promote common root rot. This includes water and temperature stresses, nutrient imbalances, and insect injury. Seedling blights often occur if seeds are planted too deep or into dry, warm soil. Warm (68-86°F), wet weather persisting for several days favors spot blotch development.
Modest resistance to common root and foot rot is available. Rotation to broadleaf crops, adoption of no-till production, and proper planting depth can be beneficial. Some fungicide seed treatments help prevent seedling blight and provide some protection against root and crown rot. This protection lasts about three weeks from the time of planting, after which infection may occur. Potash can reduce spot blotch.