Southern Rust Makes Its First Appearance in Kansas Corn
After a relatively slow start to the growing season, southern corn rust has officially arrived in Kansas.
The disease was recently detected at trace levels in Stafford County on July 20, 2026, marking the first confirmed report of southern rust in the state this year. While southern rust often appears in Kansas by early July, the 2026 season has developed much more slowly than normal, and disease levels remain lower than what we typically see by late July. The first confirmed test of southern rust in southeast Kansas was in Bourbon and Crawford on July 22, 2026.
Unlike several other common corn diseases, including tar spot and gray leaf spot, southern rust does not survive Kansas winters. Instead, the fungus is carried north each year on wind currents from tropical and subtropical regions. Once it arrives, however, favorable weather can allow the disease to spread rapidly.
Warm temperatures near 90 degrees, humid conditions, and warm nights create the ideal environment for southern rust development. As summer heat settles across Kansas, growers should begin paying close attention to their corn fields.
Fortunately, much of the corn in eastern Kansas has already reached or passed the optimum fungicide application window, reducing the likelihood of significant yield losses. The situation is different for later-planted corn in central and western Kansas, where fields remain vulnerable and should be scouted regularly over the coming weeks.
One question many producers ask is whether they should apply a fungicide before finding the disease. The answer is generally no. Preventive fungicide applications specifically for southern rust are not recommended before the disease has been detected. Instead, regular field scouting is the best management strategy. Once the characteristic orange pustules appear on leaves, the disease can reproduce quickly under favorable weather conditions.
When deciding whether a fungicide application is warranted, growers should consider several factors, including hybrid susceptibility, the number of infected plants, and the crop’s growth stage. Early infections on susceptible hybrids during favorable weather present the greatest risk for yield loss.
There is good news for producers who have already applied a fungicide at tasseling or silking for diseases such as tar spot or gray leaf spot. Most products labeled for those diseases also provide effective control of southern rust and typically offer about three weeks of residual protection. Even so, continued scouting remains important because disease pressure can increase after fungicide protection begins to decline.
Identifying southern rust is relatively straightforward. The disease produces bright orange pustules that are usually found on the upper surface of corn leaves. If you rub your finger across the pustules, the orange spores will easily come off onto your hand—a simple field test that distinguishes southern rust from many other leaf diseases.
To help producers stay informed, the Kansas Corn Commission and K-State Plant Pathology have developed an online Corn Disease Resource Center that allows growers to monitor diseases affecting corn across Kansas. The interactive map highlights where diseases have been confirmed and can help producers determine what threats may be approaching their area.
State specialists are also asking for growers’ assistance in tracking southern rust. If you suspect the disease is present in your field, contact your local K-State Research and Extension office or submit a sample to the K-State Plant Disease Diagnostic Lab. Reports from across the state help researchers monitor disease movement and provide timely recommendations to Kansas corn producers.
As we move deeper into the growing season, regular scouting remains the best defense. Early detection, combined with timely management decisions, can help protect yield potential if southern rust continues to spread across Kansas.
Lonnie Mengarelli is a Kansas State University Extension Agriculture agent assigned to the Southwind District. He may be reached at [email protected] or 620-223-3720.
*The use of trade names is for clarity and educational purposes only and does not imply endorsement by K-State Research and Extension. Always read and follow current pesticide label directions.
