5 Critical Insights From The Southern Rust Rampage In Midwest Corn

Northeast Iowa farmer Elliott Henderson sprayed a fungicide on part of his corn crop three times this season and nearly all of his crop twice, battling to break the chokehold of southern rust in his fields.

Henderson, who farms in Buchanan County, wasn’t alone in his struggle to contain the disease. Iowa State University (ISU) Extension estimates southern rust reached all 99 counties in the state.

Most corn growers were aware of the disease but hadn’t experienced the ruthless destruction it could cause.

For many, that changed this season.

The farmers Henderson routinely connects with are finding extreme yield losses now, as they start combining a corn crop that in many cases dried down and died prematurely. What occurred is common to southern rust – the disease pustules ruptured corn leaf surfaces, making it hard for plants to retain or regulate moisture.

“I made some calls around to see what guys are getting, and yields are down. I mean, we’re talking 30 to 60 bushels,” says Henderson. “We’re seeing guys with a 240-bushel APH, and they’re talking 180-bushel corn.”

Yield losses of up to 45% can occur from southern rust in severe cases, according to the Crop Protection Network (CPN).

Along with the yield loss, Iowa test weights are also taking a hit and could result in lower prices for growers. The official minimum test weight in the U.S. for No. 1 yellow corn is 56 lbs. per bushel and for No. 2 yellow corn is 54 lbs. per bushel, according to Purdue University Extension.

Henderson says he’s hearing farmers share test weight numbers well below those.

“We’re seeing lows in the 40s, some upper 40s, so it’s definitely being affected,” he says.

A Perfect Storm Of Disease Pressure
Plant health issues were the biggest challenge many corn growers in the Midwest encountered this season, Randy Dowdy contends.

“It was not a pollination issue. It was not a kernel development issue. We didn’t see the tight tassel wrap. It was disease pressure — that was by far the limiting factor for growers this year,” says Dowdy.

When he participated in the Pro Farmer Crop Tour in mid-August, Dowdy says he saw corn crops from Ohio to Iowa that were affected by multiple diseases. The four main ones were southern rust, gray leaf spot, northern corn leaf blight and tar spot — sometimes all four were on the same leaf in Iowa.

“Those growers that sprayed and stayed on it and understood that a fungicide couldn’t last but for 21 days at best, and made multiple applications, I think they’re going to reap the benefits,” says Dowdy in this week’s Breaking Barriers With R&D podcast.

You can watch this episode of the podcast on YouTube: Breaking Barriers with R&D: Late-Season Wins and Soil-First Strategies

(CPN)

Both Dowdy and David Hula, business partners in Total Acre, lament that many Midwest growers didn’t take a cue from their southern brethren and spray fungicides multiple times this season.

“Industry, in general, says if you spray at VT or tassel time, you can get by with one time. That is mostly accurate under a normal weather year,” Hula says. “But this year [some Midwest states] just had that explosion of southern rust, so they were dealing with a disease that’s historically not been a problem. You just had the environment for it.”

With growers beginning to plan what to do next season, Dowdy and Hula spent some time this week considering how growers can build an effective agronomic management plan for 2026.

Here are five of their key takeaways:

1. Formalize a plan to address disease (and pests, too).

“You have to stay proactive with your scouting and be willing to go with earlier fungicide or multiple applications, depending on what shows up,” Hula says.

In the process of being prepared to make multiple applications, keep in mind that you might not need all of them. While tar spot overwinters in stubble, southern rust doesn’t. The latter might not be a severe problem next season, as it is blows in from warmer climes.

Dowdy believes the weather system bringing southern rust to the Midwest this season originated in the Delta.

“Let’s face it, the incubator for you was the fact that you were wet and then had high, nighttime temperatures. It was hot, and you had corn everywhere, and you had a perfect environment,” he says.

Henderson agrees, noting moisture at the wrong time and too much heat were factors.

“We had a lot of heat right after pollination into that blister stage. We were stacking GDUs up really fast on that early-planted corn,” he recalls. “I do think some of this later planted corn is probably going to have a better experience finishing out.”

2. Work with like-minded farmers, agronomists and industry experts.

Be aware of disease pressure that is around you or headed in your direction by tapping into a local agronomist or groups such as the Crop Protection Network, and stay abreast of what’s happening in other regions.

“Everybody here is on pins and needles about southern rust every season, and we are constantly getting feedback from county [Extension] agents and industry, who are pushing the information out to the farmer, because everybody is well aware of the ramifications of southern rust,” Dowdy says.

Henderson, who works with Dowdy and Hula via their Total Acre program, also has a network of farmers in Iowa that he connects with on a regular basis.

“It’s a network of dozens of us farmers that call each other, bounce ideas off each other,” he says. “The things we’re talking about are often time-sensitive. It can be a daily thing.”

3. Understand how to use fungicides for maximum ROI, if you have given them little consideration in the past.

“It’s all about coverage,” Dowdy says. “Drone applications can be fine, but no matter what you do, if a guy is spraying two to three gallons, and you compare it to a ground rig spraying 15 to 25 gallons, I mean, there’s just no comparison in that coverage.”

Another aspect of coverage, Hula adds, is making sure the fungicide gets into the plant canopy far enough to have the desired effect.

“Fungicides have a tendency to work from the leaf they’ve come in contact with and move up,” Hula says. “So, if you’re trying to protect at least that ear leaf – and I like to protect the leaf opposite and below the ear – you’ve got to get penetration with that product.”

For a drone application, Hula says growers might have to spend a couple extra dollars to get sufficient volume for the product to get down below the canopy.

“If that’s what needs to be done, let’s do it,” he encourages. “If I’m spending $30 or more an acre, then I want to at least have the success that I’m paying for.”

4. Use products labelled for the disease issue you face.

That sounds like a no brainer, but in the heat of battle the wrong product can get applied, or you can select a product that isn’t up to the task.

With a tough disease like southern rust or tar spot, using newer chemistries with more than one active ingredient is also a plus.

5. Stay with your crop throughout the season; don’t walk away.

Today’s corn genetics tend to have more back-end potential to add yield through kernel fill.

It’s a key reason to evaluate what a fungicide application can do for a crop that’s advanced into one of the later reproductive stages, say Hula and Dowdy.

Brian Herbek, who farms near DeWeese, Neb., has leaned into their advice the past few years.

“I found out a couple of years ago, there’s a lot of hidden yield out there that a lot of us leave on the table,” Herbek reports.

What he learned from Hula and Dowdy is corn has the genetic ability – some hybrids more so than others – to pack starch into its kernels late-season to create higher test weights.

He scouts corn late-season to decide where to make “the finishing pass,” an application of fungicide or nutrients or some combination of the two.

“It’s not for every field. I’ll tell everybody that right now, there are certain fields that don’t deserve that attention,” Herbek says. “But if you know what you’re looking for, and you have that potential, that application does makes sense, but you’ve really got to know what’s out in your field.”

Dowdy and Hula share additional thoughts on how farmers can improve next season’s corn crop in the face of disease pressure in the latest edition of their Breaking Barriers With R&D podcast on Farm Journal TV and YouTube.

More ideas and recommendations are available from the two corn yield champions on the Tuesday morning edition of AgriTalk with Host Chip Flory. Catch their discussion here:

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