Southern rust swept through the Midwest this past summer, taking big bites out of corn yield potential and forcing many growers to consider making late-season fungicide applications they hadn’t budgeted for.
Now, many farmers are asking themselves and their agronomic advisers how to plan for next season. A common question: Is southern rust going to be a significant problem in the Midwest again in 2026?
The answer: No one knows. Southern rust does not overwinter in crop residue – it has to blow in on winds from southern climes to be a problem for Midwest growers. So, what happens next year with the disease depends largely on how Mother Nature behaves.
Another fun weather fact from summer of 2025...
— Pioneer Troy (@deutmeyer_troy) November 18, 2025
Chart showing why disease pressure was at biblical levels in areas this summer. Over two months of humidity levels WAY above average.
Mid June until beginning of September, nearly every day was above average humidity (blue line)… pic.twitter.com/eFHEDs4hs1
Fungicides Paid Their Way
If there’s any silver lining to the challenge many farmers had with southern rust this year it’s that now almost everyone knows how yield-crippling the disease can be and the value fungicides can deliver.
Mary Gumz says she was fielding calls from concerned corn growers as early as the V10 to V12 growth stages of corn.
“It was a very different scenario than we’re usually in most years, and we were recommending that farmers spray earlier than usual,” recalls Gumz, a Pioneer agronomy manager.
With the tough economics farmers faced this season, some opted to forgo an application. But where corn growers made the hard call and applied fungicide, those fields delivered at harvest.
“We got some big yield increases, and you could visually see the difference between those plants where we did make the early call [with a fungicide application] compared to the usual application at tassel timing,” she says.
Another factor that made southern rust so difficult to control this season is that, in many cases, a second application of fungicide was warranted where the disease had time to rebuild.
“You can get about two or three weeks of efficacy from a fungicide on southern rust, but don’t expect you’re going to get season-long control,” says Randy Dowdy, Valdosta, Ga., and partner in Total Acre. “I’m not aware of a fungicide that you can spray at tassel for southern rust and that will last 50, 60 days or until black layer.
Proactive Planning For Next Season Can Help
While southern rust is a concern, Kim Tutor, BASF technical marketing manager, encourages farmers to keep in mind those tough diseases, such as tar spot, northern corn leaf blight and gray leaf spot, that are annual disease challenges in the Midwest.
Tar spot overwinters in corn residue, ready to rebuild in corn crops when weather conditions are favorable to its development, and is making its way across the Corn Belt.
“Tar spot can be infecting a corn plant, causing damage internally for two to three weeks before we are able to detect a lesion or see symptomology on the surface of the leaf,” Tutor adds.
She says if you are in a situation where models show significant disease pressure is moving into your area or you are based in an area with tar spot pressure, for instance, to consider making an early application with a fungicide that has residual control during what she calls an optimized application window – as early as V10 and through at least R3.
If you are in an area with heavy tar spot levels or you are looking to push the envelope for yield, Tutor recommends making two fungicide applications in corn, keeping applications 20 to 28 days apart.
As for which fungicide you apply, for so-called driver diseases like tar spot or southern rust, Missy Bauer, Farm Journal Field Agronomist, recommends going with what she describes as “Cadillac” type chemistry, newer technology that features multiple modes of control.
Extension plant pathologists annually update fungicide efficacy ratings for various crops, including corn, via the Crop Protection Network website. You can check the ratings for each fungicide’s performance on various diseases using the Corn Fungicide Efficacy table. Some products work better on tar spot or gray leaf spot, whereas others are more effective on rusts and other diseases.
Given the outlook for grain prices next year, be sure to also check out the new Corn Fungicide ROI Calculator on the Crop Protection Network.
You can use the calculator to look at different scenarios (grain prices, expected yield, disease severity) to see the potential ROI on fungicide applications.
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