How do you estimate yield in a field where 5,000 plants are already dead? It’s the kind of question Eastern Corn Belt growers are facing now after June rains, summer heat and late-season disease created one of the most variable corn crops in recent memory — and it’s why preharvest scouting could be some of the most valuable time you spend before firing up the combine.
Farm Journal Field Agronomists Ken Ferrie and Missy Bauer say getting into fields now will do more than help you estimate yield. It could also help you decide which fields to harvest first, where standability could become an issue and whether seemingly high-yielding fields have more crop damage than you expected.
Early-Season Stress Sets the Stage
Ferrie, who works with growers across Illinois, says his customer base is currently estimating corn yields 20 to 40 bushels per acre below last year. There are still pockets of impressive corn, he notes, but the season’s early- and mid-season stresses have left a much less uniform crop.
He told Farm Journal’s Clinton Griffiths and Tyne Hulsey during the podcast Unscripted that the trouble began in early summer.
“Definitely started in June, with a lot of cases of 14-plus inches of rain,” Ferrie says. “That’s just too much water to throw at the crop.”
In some Illinois fields, saturated soils left corn roots without adequate oxygen for nearly two weeks during a critical period for ear development. Nitrogen losses added to the stress.
“When you take on the water damage and then add the heat to it, if a hybrid got caught in that heat, that’s probably the one that cost all fields, no matter how much rain you did or didn’t get in there,” Ferrie says.
The combination of too much water and heat shortened ears in some areas and reduced the crop’s ability to recover. It also exposed differences among hybrid genetics and planting dates, making field-to-field variability particularly difficult to assess.
Heat Pushes Crop Toward Rapid Maturity
As you assess yield potential, Bauer and Ferrie say to keep an eye on how quickly the crop is moving toward maturity.
Ferrie says some April-planted corn in parts of Illinois was 24% to 25% moisture just over a week ago and then dropped to 18% last week.
“The stuff that’s at black layer is going to dry in the field pretty quick,” he says. “The stuff that’s not at black layer, though, it’s going to move along a little faster. Hopefully, it doesn’t come at too much expense of grain fill.”
That rapid finish makes harvest timing even more important.
Bauer’s Michigan growers are dealing with a different moisture story. After substantial rainfall earlier in the season, conditions turned dry during the second half of July and into August.
“We’ve just kind of been barely hanging on,” Bauer notes. “We get a little rain, but just not quite enough.”
Even with the dry finish, Bauer says the Michigan crop is relatively close to normal production levels. She expects corn yields to be similar to last year, with better crop uniformity helping offset slightly shorter ears than usual.
Disease Pressure Adds to Harvest Challenge
The 2026 corn crop’s final weeks in the field aren’t necessarily going to be easy.
Bauer says disease pressure was relatively light through much of the summer in her area after hot, dry weather reduced humidity levels. Tar spot, however, is now beginning to increase as more humidity is present.
Watch Crown Rot of Corn CPN TV at https://t.co/O9IDErOWgJ.
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In Illinois, Ferrie is seeing another problem that is becoming increasingly difficult to overlook: crown rot.
“Crown rot continues to increase in scale each year,” he says. “More and more fields are infected with it, and you see it across more and more acres.”
What makes crown rot particularly challenging is its timing. An infection typically occurs in the crop months before symptoms become obvious, a result of wet conditions, Bauer adds.
“Those infections likely happened back in June, and we’re just really now seeing the effects of them,” she explains.
Bauer recalls the 2021 season, when crown rot combined with severe tar spot infections in some fields and produced devastating losses.
“If the plant can’t fill ears, it can be extremely dramatic result,” she says.
Adjust Your Yield Calculations
Ferrie notes that dead corn can be a challenge for farmers to estimate accurately in their yield estimates. He says growers shouldn’t simply count every plant equally when a field contains significant numbers of dead or severely compromised plants.
For example, a field with 30,000 plants per acre might have 5,000 plants with dead stalks and drooping ears while the other 25,000 plants remain standing. The affected ears need to be sampled separately because they are likely to have substantially poorer grain fill.
“Those with the ears hanging down, they’re going to be 90 to 100,000 [kernels per bushel] pretty easy,” Ferrie says. “So, if you ignore them and give them the same weight, you’re going to way overshoot your yield estimate.”
That can quickly erase 20, 30 or even 40 bushels per acre from your yield estimate.
“If you know right away that you got 5,000 plants in the field that aren’t going to pass the ‘push test,’ it also kind of helps you rank your fields,” he adds.
With weakened stalks and down corn likely to be part of the harvest picture in some areas, ranking fields could help you prioritize fields for harvest before agronomic problems become more costly.
“The value of that pre-harvest scouting could be huge this year for a lot of growers,” Bauer says.
Fertility Cuts Show Up at Harvest
There is another lesson emerging from 2026, and it starts with decisions farmers made last spring prior to planting.
High fertilizer prices prompted many growers to look for places to trim costs. Ferrie says cutting nutrients based on soil-test information can be a reasonable strategy. The problem came when growers cut nitrogen and sulfur without accounting for how those nutrients would be supplied later — or how much could be lost during a wet season.
“Definitely in the corn side, it came down to nitrogen and sulfur,” Ferrie says.
Some growers moved more nitrogen into their fall applications because it was less expensive. But after the excessive June rainfall, some of that nitrogen was gone by the time the crop needed it.
The sulfur situation was challenging, as well. The atmospheric sulfur deposition has declined dramatically over time, meaning corn growers can no longer count on the atmosphere to supply what crops need.
That makes sulfur management increasingly important, particularly on lighter soils and in seasons with heavy rainfall that can flush available sulfur from the root zone.
The caution, say Bauer and Ferrie, is to make nutrient cuts only when you have a clear understanding of what the crop needs and how you’ll handle replacing that nutrient if heavy rains deplete it during the growing season.
Let Data Guide 2027 Decisions
Those lessons will matter as you begin making decisions for 2027, add Ferrie and Bauer.
Bauer recommends going back to soil tests and evaluating where fertilizer reductions make sense. She also says you should consider whether it makes sense to lock in portions of your fertilizer needs now, particularly if prices continue to move higher.
The goal is to avoid making a short-term input saving that creates a much larger yield loss later.
“Try to make sound decisions based off of real numbers, real data,” Ferrie advises. “Don’t let the emotions run you over when you’re thinking about how you’re going to trim back your fertilizer costs.”
That same thinking should apply to any major change in production practices made to capture a premium or reduce costs.
“Let the numbers do the talking for you,” he says.
For Bauer, the biggest lesson from 2026 is the importance of staying with the crop all the way through the season, even when conditions make that difficult.
“Try to take the crop from the beginning to the end and not walk away from it,” she says.
Ferrie agrees. A good cropping plan is only a starting point.
“You do all the planning in the world, but if the plan doesn’t quite work the way you want it, you have to be prepared to make adjustments to make sure we don’t leave any more bushels out there than we have to,” he says.
