There are many disease organisms that can reduce corn yields in Kansas. One of the stealthiest is the root-lesion nematode (RLN) because it operates below ground on the roots and often has no specific, identifiable symptoms other than yield loss. It is present, at some level, in nearly all corn fields in the state. Historically the largest yield losses, which can exceed 40 percent in individual fields, occur in western Kansas where irrigated, no-till, continuous corn production systems in sandy soils are common.
Like most nematode problems, visible symptoms, if any, may be limited to patchy areas of the field where growth is stunted. Sometimes yellowing may also occur (Figure 1). Occasionally, roots may have lesions on them or roots may appear to be pruned (Figure 2).
Figure 1. Yellowing of plants caused by root-lesion and other nematode injury. Yield in the center of these areas was as low as 30 bu/ac. Photo courtesy of Tamra Jackson-Ziems, University of Nebraska-Lincoln.