By Scout Nelson
University of Minnesota Extension specialists recently discussed whether foliar corn diseases could threaten crop yields during the March 4, Strategic Farming Let’s Talk Crops webinar. The session focused on disease risks and management strategies for the 2026 growing season.
The discussion was led by UMN Extension educators Angie Peltier and Ryan Miller along with UMN Extension corn and soybean plant pathologist Dean Malvick. The Strategic Farming webinar series continues through March, and registrations are still being accepted: https://z.umn.edu/SF2026. To watch this episode, visit: http://z.umn.edu/StrategicFarmingRecordings.
Experts explained that several foliar diseases can affect corn yield potential in Minnesota. Among the most important diseases discussed were tar spot, southern rust, northern corn leaf blight, and Goss’s wilt and blight.
Tar spot remains a disease of concern since it first appeared in the United States in 2015 and in Minnesota in 2019. The disease is caused by the fungus Phyllachora maydis, which survives infected crop residue. Spores released during the growing season can spread infection and reduce yield potential under favorable weather conditions.
Tar spot is often favored by moderate temperatures and humid conditions. Researchers continue developing predictive models to help farmers better estimate disease risk. Selecting resistant hybrids and using properly timed fungicide applications are key management strategies.
Another disease discussed during the webinar was southern rust, which has increased in prevalence in recent years. Unlike tar spot, the fungus that causes southern rust cannot survive Minnesota winters. Instead, spores travel north each growing season. Warm temperatures above 80 °F and humid conditions favor the disease.
Northern corn leaf blight was also highlighted as a disease that can develop during cool temperatures and extended leaf wetness. Farmers can reduce risk by selecting resistant hybrids and applying fungicides when disease pressure increases.
Experts also noted that Goss’s wilt and blight previously caused serious yield losses in parts of Minnesota. Improved hybrid resistance has reduced its impact, although the disease still appears in some regions.
Researchers also reported that Curvularia leaf spot, a newly identified corn disease in Minnesota, was detected in 2025.
Field research conducted between 2023 and 2025 examined how fungicide timing affects disease control. Results suggest that a single well-timed fungicide application around tasseling often provides the best economic return compared with multiple treatments.
Photo Credit: gettyimages-luc-pouliot
Categories: Minnesota, Crops, Corn