The weather conditions of 2025 were perfect for a southern rust outbreak across the Midwest, resulting in many growers needing to make late-season decisions on disease management. Southern rust is a fungal foliar disease that flourishes in hot and humid conditions; it requires a living host to reproduce. The spores are typically blown from the south by wind and rain. In a recent Pioneer webinar, 86 percent of attendees said they experienced southern rust in 2025 and almost 50 percent dealt with southern rust at least once from 2020 to 2024.
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Southern rust making big impact
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Southern rust has small circular, pinhead- shaped pustules that are reddish-orange.
Both rust diseases of corn can cause substantial yield losses under severe disease pressure. But southern rust generally poses a greater risk to corn yield than common rust, making proper identification important.
Later in the season, P. polysora forms darker pustules called telia that contain teliospores.
In recent growing seasons, southern rust is occurring further north in the Midwestern United States earlier in the season than has been historically typical for this disease.
Southern rust infects the upper leaf surface, as well as stalks and husks. It's favored by warmer temperatures of more than 77 degrees.
Southern rust is now routinely observed in Indiana, Illinois, Iowa, Nebraska and Kansas, and has been detected as far north as South Dakota, Minnesota and Wisconsin.
