Southern Rust Makes Big Midwest Impact as It Expands Northward

Photo by Kiersten Wise

In 2025, southern rust made an unusually large impact across the Midwest and northern U.S. due to ideal weather conditions. This included hot, humid temperatures and record rainfall in July. The fungal disease spreads through airborne spores from the South. In a recent Pioneer webinar, 86% of farmers reported experiencing it this year.

Southern rust appears as small, light-orange pustules on the upper leaf surface. It spreads rapidly and causes premature leaf death that weakens stalks and reduces yield and grain quality. Unlike common rust, which thrives in cooler weather, southern rust develops when temperatures exceed 77°F and humidity stays high.

A persistent heat dome and high dew points in late June created near-perfect conditions for the disease’s spread, while southerly winds helped transport spores northward. Pioneer agronomists noted that southern rust can appear unpredictably, making scouting and timely fungicide application crucial.

Southern rust does not overwinter in cold conditions. It requires a living plant to survive. While there were no abnormally strong winds this season, much of the country experienced a stronger flow from the southwest in June.

Managing future outbreaks of southern rust requires a combination of genetics with resistant hybrids, crop protection with proactive fungicide programs, and data-driven approaches. A timely harvest can also help mitigate yield loss from southern rust.