If there was one thing farmers learned from the 2026 growing season, it’s that Mother Nature rarely follows a script.
After a devastating southern rust season in 2025, many corn growers entered this year on high alert. Moisture was abundant across much of the Midwest, temperatures remained warm, and conditions appeared favorable for another round of significant disease pressure. But that’s not exactly how things unfolded.
Despite favorable weather conditions, southern rust never developed into the widespread threat many expected. Instead, growers faced a mixed bag of foliar diseases, followed by late-season concerns involving stalk, crown and ear rots.
“We had so much moisture and not a whole lot of disease,” says Alison Robertson, Iowa State University Extension field crops pathologist. “It was especially interesting compared to 2025.”
Robertson and Tamra Jackson-Ziems, University of Nebraska-Lincoln Extension plant pathologist, recently discussed the season’s surprises on the I See Dead Plants podcast. Their biggest takeaway: Don’t make next year’s management decisions based solely on what happened this season.
Don’t Chase Last Year’s Diseases
After southern rust caused significant concerns in 2025, many growers applied fungicides more aggressively this season. Yet despite favorable weather, the anticipated outbreak never materialized to the same extent.
Robertson questions whether every fungicide application this year delivered enough yield protection to justify its cost. Her advice for next year? Leave untreated check strips in fields where fungicides are applied.
“Check strips are the only way that you can tell whether that treatment had an effect,” Robertson says. Keeping everything else consistent allows growers to evaluate what the treatment actually contributed and determine whether a similar application can make economic sense next season.
The disease picture in Iowa wasn’t entirely quiet. Robertson says farmers encountered bacterial leaf streak, Goss’s wilt, northern corn leaf blight, tar spot and southern rust. In Nebraska, Jackson-Ziems saw similar diseases, with tar spot becoming particularly severe in parts of central Nebraska late in the season.
Some tar spot affected corn looked ready to harvest ready but wasn’t, says Jackson-Ziems. She notes the grain moisture in some fields remained between 25% and 30%, despite the crop’s seemingly advanced drydown. Tar spot can accelerate plant death without ensuring that kernels have dried sufficiently — a critical disconnect Jackson-Ziems says is worth remembering when evaluating fields and scheduling harvest next year.
Late-Season Issues Showed Up
Some of the more consequential disease concerns for 2026 emerged late in the season, when stalk, crown and ear rots became more apparent.
In Iowa, Robertson saw considerable Fusarium ear rot and heard reports of vomitoxin concerns following a wet September. She also noted increased stalk and crown rot issues.
Plant stress likely contributed to some of those problems. Excessive moisture can lead to nitrogen loss and reduced photosynthesis, limiting the carbohydrates available for grain fill. Plants under stress may draw on sugars stored in stalks and roots, potentially leaving those tissues more vulnerable to decay, Robertson says.
Nebraska experienced a different progression. Some areas dealt with drought during the first half to two-thirds of the growing season before warmer nights, higher humidity and rainfall arrived. Jackson-Ziems observed Fusarium and Gibberella ear rots, along with occasional reports of Aspergillus and Nigrospora.
For growers, the concern extends beyond yield. Ear rots can affect grain quality and create potential mycotoxin issues. However, finding ear rot doesn’t automatically mean mycotoxins are present. Jackson-Ziems encourages growers to evaluate affected grain, consider its intended use and pay attention to storage requirements.
Grain moisture management is especially important. She recommends drying grain to 15% moisture or less for shorter-term storage, with potentially lower moisture targets — around 13% — for storage extending into warmer months. Continued monitoring is important, as temperature changes can create condensation and moisture movement inside bins.
Make Hybrid Decisions Field by Field
While farmers can’t predict which diseases will emerge next season, they can use this year’s observations to reduce risk. Both pathologists emphasize the importance of matching hybrid genetics to individual field histories rather than making seed decisions primarily around yield potential or early-order discounts.
Crown rot is one example for consideration. Jackson-Ziems says incidence reached as high as 80% in some Nebraska fields. “If you had a problem with crown rot, try and find a hybrid,” Robertson says. “Talk with your seed dealer about a hybrid that maybe has a little bit more tolerance.”
The same approach applies to foliar diseases. Selecting hybrids with improved tolerance to diseases such as tar spot and northern corn leaf blight can help reduce risk and, under certain conditions, lessen the need for fungicide applications, Robertson says.
Field records are another important part of the process. Documenting where diseases occurred — even in fields that won’t be planted to corn in 2027 — can help growers make better decisions when corn returns to those acres. Crop rotation also remains a useful management tool for diseases.
Robertson cautions against assuming that this year’s disease pressure will carry over into next season. Pathogens can survive between growing seasons, but whether they develop into a significant problem depends on inoculum levels, hybrid susceptibility and environmental conditions.
Focus on What You Can Control
Robertson says predicting exactly what diseases will develop in a given season remains difficult. It’s why she encourages growers to focus on the management decisions they can control.
Robertson encourages farmers to select hybrids with appropriate disease tolerance, maintaining accurate field records and paying attention to fundamental agronomic practices, including appropriate fertilizer rates and planting populations.
Jackson-Ziems adds that the best preparation for 2027 isn’t trying to predict which disease will show up next — it’s knowing which diseases have challenged individual fields and then choosing hybrids and management practices accordingly.
Hear more of Jackson-Ziems and Robertson’s insights from their podcast discussion, available at the link below:
