Key takeaways from 2025 growing season

WESTFIELD, Ind. — Southern corn rust is generally considered a “tropical disease,” but there were unusually widespread reports of the fungus across Indiana and Illinois in 2025.

According to Integrated Pest Management Platform for Extension and Education, southern rust was confirmed in 20 Illinois counties in late July. The reports ranged from Jackson County in southern Illinois to Jo Daviess in the northwest.

Southern rust was found in nearly 40 Indiana counties last year, with confirmations ranging from late August to early September. The disease was confirmed as far north as Elkhart County to Posey County in southwest Indiana.

“Southern rust is not a new phenomenon, requiring consistent management in the southern states. However, weather in 2025 supported a widespread outbreak of the fungus in the Midwest,” said Steve Crafton, LG Seeds agronomist.

Southern corn rust can occur in major regions for corn production in the United States. High humidity and temperatures around 80 degrees create a supportive environment for it to thrive.

Each year, wind currents from tropical areas carry rust spores north and begin new infections. When conditions favor rust development, the infection cycle continually repeats and causes secondary infections.

The period between when a plant is infected and when the fungus develops pustules and spores can be as short as nine days when conditions are favorable. Each pustule can produce spores for up to eight days, distributing thousands of spores that can cause secondary infections.

“This was an amount of southern rust that I had not experienced in my career,” Crafton said, noting it contributed to significant yield loss in some areas.

This fungus does not overwinter in northern Illinois. Crafton said this helps reduce the likelihood of a repeat in 2026 for this geography.

The southern rust fungus uses the plant’s nutrients for growth and reproduction, which affects grain fill. Yield losses as high as 45% have been reported when the disease in severe.

Symptoms are similar to common rust, but pustules are smaller and occur almost exclusively on the upper leaf surface. Pustules are usually circular or oval, very numerous and densely scattered over the leaf surface.

Spores are orange when they erupt from the pustule. As pustules age, they become chocolate brown to black, often forming dark circles around the original pustule.

To protect corn crops, foliar fungicides labeled for southern corn rust are available. Hybrids and inbreds showing resistance are also useful.

Heat Toll

High temperatures took a toll this past growing season. The prevalence of high temperatures from May through September impacted plant resilience.

“In Peoria, there were 25 days between July 1 and Aug. 15 where nighttime temperatures remained above 69 degrees,” Crafton said, explaining that corn plants struggle to rest at those higher temperatures.

“The corn plant needs lower temperatures at night to rest and respire — that can tamper with grain fill.”

Corn Rootworm

Corn rootworm is a consistent challenge, and while 2025 did not feature any major differences, corn growers need to remain vigilant against this pest.

“I completed some root digs and did see worms feeding,” Crafton noted, explaining that products with three traits to combat the pest have been shown to hold up well against corn rootworm pressure.

Protection Selection

Even though some challenges are beyond growers’ control, there are some traits and management tips they can focus on heading into the new year.

“Challenges come in waves. You never know what nature will throw at you,” Crafton said. “When we face a novel challenge, it can be tempting to overcorrect and prioritize products that solve for that one issue.

“We’re not going to see the same challenges every year — that’s why choosing products that have shown strong yield performance year after year and aligning them to your soils and management practices should be a priority.”

His advice is to spread maturity, diversify seed and prioritize harvest.

“There will be some fields as you scout that you know will need to be harvested first and others that will stand strong well into harvest,” he said.

Growers need a mix of corn seed products to keep maturity spread and preserve plant yield potential.

In-Season Management

What is the key to achieving those high yields? According to Crafton, in-season management is critical.

In 2025, you couldn’t discount a good fungicide program. Ways to save are always top of mind, and forgoing fungicide may have looked to be an appealing avenue; however, Crafton warns against this.

“Fungicide may help reduce the expansion of disease in the upper canopy, which is critical for setting the plant up for later success. Even one pass can make a difference. A healthier plant is better able to fill kernels and stand strong until harvest,” he said.