Corn growers across the U.S. can find themselves battling two different kinds of corn rust: common corn rust and southern corn rust. Common corn rust, as the name implies, is more prevalent than southern corn rust — but southern corn rust is more likely to cause catastrophic yield loss. Learn how to differentiate between these two fungal diseases and how to effectively manage each type.
Common corn rust
Common corn rust cost growers nearly 2 million bushels of yield in 2025.¹ Common rust spores can overwinter in subtropical and tropical regions with wind distributing spores that eventually reach the Midwest. Common rust develops best in high humidity with night temperatures of 65 to 70 F and moderate daytime temperatures.²
The earlier common rust develops, the greater the potential yield loss. Severe common rust damage can kill leaves and subsequently result in poor-quality grain at harvest. Common corn rust is a greater threat to seed corn than it is to other corn hybrids (though southern corn rust is an even greater threat to seed corn yields).
Symptoms of common corn rust
Chlorotic, fleck-like lesions are scattered sparsely across both upper and lower surfaces of leaves. As these small, tan lesions grow, fungus spores erupt from the lesions through the leaf surface. As a common rust infection progresses, pustules darken, ranging from red-brown to dark red. These pustules are powdery and rub off when touched. Leaf tissue encircling the pustules often turns yellow or dies, leaving lesions of dead tissue and creating a characteristic yellow halo. Corn husks, leaf sheaths and stalks also may be infected with common rust.
Southern corn rust
Southern corn leaf rust pustules stay mainly on the upper leaf surface and are bright orange to light brown. The disease thrives in warmer temperatures (high 70’s to low 80 F, while common rust thrives best when temperatures range from mid 60 F to low 70 F). Southern rust was responsible for an unprecedented 500 million bushels of yield loss to U.S. growers in 2025, when it spread rapidly due to ideal environmental conditions for the disease: heat and high humidity.³ Uncontrolled infections can significantly impact grain fill and yield, making early identification of southern rust symptoms vital.
Corn rust management strategies
A combination of tactics can help you proactively reduce the risk of rust impacting your yield.
- Identify which rust you’re dealing with: Common and southern rusts are like fraternal twins — the same but different. Carefully determining which specific rust is impacting your crop will help you tailor your control plan to maximize its efficacy. Early detection and differentiation are key.
- Select rust-resistant corn hybrids: Typically the best management practice is to use resistant corn hybrids. Later-planted sweet corn and seed corn can be particularly susceptible to rust and experience severe yield losses.
Fungicides: When applied earlier in the season, before too many pustules are apparent, fungicidal treatment can help manage common rust, reducing the rate of disease development and spread.
- For common rust, spray when 80% of leaves show one or more pustules.
- For southern rust, spray when 50% of leaves show one or more pustules.⁴
Foliar fungicides such as Veltyma™ fungicide are very effective in preventing further spread of rust. Unfortunately, fungicides are typically less effective to manage southern rust, and it requires higher application.⁵
Southern rust also usually emerges late in the season, meaning you have to navigate pre-harvest interval (PHI) restrictions when planning applications. Veltyma™ fungicide PHI for corn is 21 days, for example, while PHI for some other fungicides is as long as 30 days.
- Cultural practices: Avoiding late planting or selecting shorter-season hybrids can give your cornfield a head start on reaching more advanced maturity by the time the rust spores settle.
Experts are available to help you make your decisions. Reach out to your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.
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Endnotes
- Sikora, Ed, et al. “Corn Disease Loss Estimates from the United States and Ontario, Canada — 2025.” Crop Protection Network, 6 Mar. 2026, cropprotectionnetwork.org/publications/corn-disease-loss-estimates-from-the-united-states-and-ontario-canada-2025. Accessed 13 Sept. 2026.
- “Common Rust of Corn.” Crop Protection Network, 19 Mar. 2019, cropprotectionnetwork.org/encyclopedia/common-rust-of-corn. Accessed 13 Sept. 2026.
- “Common Rust of Corn.” Crop Protection Network.
- Ahumada, Daisy. “Corn Rusts: Common and Southern Rust.” NC State Extension Publications, 27 Sept. 2023, content.ces.ncsu.edu/corn-rusts-common-and-southern-rust. Accessed 13 Sept. 2026.
- Ahumada. “Corn Rusts: Common and Southern Rust.”
