This disease is a significant threat wherever corn is grown after corn. The fungus survives between growing seasons in residues of corn leaf blades and sheaths. From there, it is spread by wind and rain to leaves of the new corn crop. Thus, in the absence of crop rotation, susceptibility to gray leaf spot should be carefully considered when selecting a hybrid. Hybrids exhibit differing levels of partial resistance to gray leaf spot.
Partial resistance is the most common type of disease resistance in field crops.
Varieties with partial resistance are those that, under uniform conditions, exhibit less disease than some standard cultivar or host line. Gray leaf spot will still develop on a partially resistant hybrid, but it typically is slower to develop and less severe. For example, compared to a fully susceptible hybrid, a hybrid with partial resistance will usually have fewer lesions for a given spore load, and those lesions will be smaller. This reduces the impact of the disease on crop development and yield. When growing continuous corn, always select hybrids with as high a level of resistance as you can against gray leaf spot.