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Southern rust is most common in Southern states but can threaten plant health and yield potential throughout the Corn Belt. Though less common than common rust, southern rust is typically more severe—making accurate identification essential for effective management. Southern rust can be mistaken for common rust, but several visual differences help distinguish them:
- Southern rust pustules are typically limited to the upper leaf surface, while common rust appears on both upper and lower leaf surfaces.
- Southern rust pustules are orange to reddish-orange, while common rust pustules are red to cinnamon brown.
- Southern rust pustules have a circular shape, while common rust pustules tend to be elongated and jagged.
Rust pathogens do not overwinter in the Corn Belt. Instead, they develop in southern cornfields and move northward viawindblown spores carried by prevailing weather patterns.
Yield loss from southern rust depends on infection timing, the severity of leaf damage, and where on the plant that damage occurs. When upper leaves are affected early in the growing season, yield loss can be significant. If infection is limited to lower leaves or happens late in the season, the impact on yield is typically minimal. Consequently, later-planted corn is generally at higher risk for yield loss due to foliar disease pressure.
If southern rust is confirmed, growers should consider the following actions:
- Consider fungicide application. If applied properly and in a timely manner, fungicide treatments can be effective in protecting corn leaves from foliar diseases. It’s critical to apply fungicides with the correct water volume for maximum disease control.
- Aproach® Prima fungicide has two modes of action that provide excellent control of this disease. Farmers should consult their local ag retailer or Corteva Agriscience representative to determine when an application of Aproach Prima fungicide makes sense for their acres.
- Choose resistant varieties. According to the University of Nebraska, resistant corn varieties are the most cost-effective means to manage southern rust in field corn1. When making seed decisions for the next season, consider planting resistant varieties.
1University of Nebraska-Lincoln CROPWATCH. 2022. Southern Rust. https://cropwatch.unl.edu/plantdisease/corn/southern-rust
Aproach® Prima is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions
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