An Iowa State University Extension agronomist says inconsistent summer conditions helped limit overall corn disease impact in east central Iowa, even as several pathogens found favorable weather at times.
Rebecca Vittetoe reported that fields showed signs of multiple issues, including northern corn leaf blight, tar spot, gray leaf spot, and bacterial leaf streak. She also noted a small amount of southern rust. According to Vittetoe, the lack of a single, dominant disease likely reflects the season’s back-and-forth weather patterns.
She said tar spot could become more noticeable later in the season as temperatures drop. The extent of yield effects will depend on crop stage, she added. Corn that is already in the later reproductive stages, especially by R6, is less vulnerable than crops that encounter disease pressure earlier during grain fill.
Corn disease impact and late-season scouting
Vittetoe advised growers to scout ahead of harvest to identify fields with higher disease pressure. Prioritizing those acres can help address potential stalk integrity and standability problems before they complicate harvest operations.
She said timely field checks will be important as the season winds down, particularly where tar spot or other foliar diseases are present.