By Pierce Paul, Ohio State University Extension plant pathologist
In Ohio, several foliar diseases are of greater concern in late-planted corn for a number of reasons.
- For diseases like gray leaf spot (GLS), northern corn leaf blight (NCLB), and eye spot that are caused by pathogens that overwinter in corn stubble, delayed planting allows more time for inoculum (spores) to buildup, especially in no-till, corn-on-corn fields.
- For diseases like common and southern rust that are caused by pathogens that do not overwinter in Ohio, planting late allows more time for spore for blow up from southern states. So, with late planting, not only are more spores likely to be available to infect the crop, they are also more likely to infect the crop at an earlier growth stage and under conditions that are more favorable for disease development. Let us use gray leaf spot as an example. In a “normal” year, although lesions may develop early in the season, this disease typically takes off and spreads after pollination (VT/R1) when the number of spores in the air is high and the weather becomes favorable for infection.