Root rots of corn
Corn root rots are very common and are caused by several soilborne pathogens such as Pythium, Fusarium, and Rhizoctonia spp. Root rots occur to some extent in every field, causing economic losses under wet conditions. Aboveground symptoms include stunting, uneven growth, chlorosis, small or poorly filled ears, or wilting. In saturated conditions, effects of root rot are difficult to distinguish from the effects of oxygen deficiency and poor root development. Root symptoms are more reliable for diagnosis. Initially, small yellow-brown lesions develop on roots; roots later turn dark brown and are obviously decayed. Fine root decay may not be apparent without careful examination. Fine roots slough off after rotting; their absence is another root rot symptom.
Root rot is generally reduced by standard seed fungicide treatments on corn. Planting corn when soil temperature is above 50°F and soil moisture is not excessive also may reduce risk. Symptoms of Pythium root rot. Image: A. Robertson
Rotted roots resulting from Pythium infection. Image: C. Grau