As farmers reflect on the 2025 growing season, one disease stands out: southern rust. It's a fungus that grows on corn.
The fungus spread not only into northern Missouri but also Iowa and even Minnesota. The disease is not new, but it's unusual for it to spread this far north, because it cannot survive harsh winters.
Oscar Perez-Hernandez, a professor of plant pathology at Northwest Missouri State University, says the disease is similar to common rust, another disease that impacts corn, causing bright orange pustules to form on the leaves.
"Compared to common rust, southern rust is a more aggressive pathogen, so you see more abundant lesions. As the disease progresses you see lesions all over the plant, even on lower leaves," he said.
Those lesions are a fungus that thrive in warm, humid conditions. Perez-Hernandez says each year winds carry the spores northward. But this year, unusually wet weather in July provided the perfect conditions for it to spread further than usual.
"From what I hear from students, local growers, and agronomists I've talked to, the disease this year was widespread,” said Perez-Hernandez.
Plant diseases need the right conditions to thrive, and each year is different.
But Perez-Hernandez expects that shifting rainfall and climate patterns will make the disease more common.
"Some pathogens that we didn't see in the past survive can now survive if we have a mild winter” he said. “And that of course is tied to climate change. So, we should expect to see southern rust in the future."
Many farmers saw crop losses due to the disease, but it can be prevented with proper fungicide treatments. In future years, farmers can be prepared, says Perez-Hernandez.
"I think one thing farmers should do is scout their fields earlier than normal and be checking for reports of southern rust in Mexico and southern states, because that can be an early warning,” he said.
The disease will show up weeks or even months earlier in southern states before spreading to northern regions.
Farmers should also check their corn hybrids, as some are more resistant to rust diseases than others.
