Inconsistent Summer Weather Limits Corn Disease Impact in Iowa
Inconsistent summer weather patterns in Iowa have limited the widespread impact of several corn diseases, including tar spot, northern corn leaf blight, gray leaf spot, and bacterial leaf streak. According to Rebecca Vittetoe, an extension agronomist with Iowa State University, while these diseases are present, the fluctuating weather conditions have prevented any single disease from becoming overly prevalent. Vittetoe noted that tar spot is expected to become more common as the season progresses and temperatures cool. However, the stage of corn development is a critical factor; diseases appearing later in the R stages, particularly by R6, will have less impact on yield compared to earlier appearances during the grain fill period. This variability in weather has, in some ways, played in farmers' favor by preventing a severe outbreak of any one disease. 
