It’s a routine on repeat this time of year for Meaghan Anderson, field agronomist and extension specialist with Iowa State University. Walking fields, grabbing ears and checking stands across central Iowa. It’s something Anderson does every year around this time. And this year, she’s finding a crop that looks better in some spots than others, and a season that’s leaving its mark in ways that won’t be fully understood until the combines roll.
“This is nice looking corn,” Anderson says while holding a couple ears from a Central Iowa corn field. “Some of the corn I’ve looked at today has been a little questionable, but this is really nice-looking corn.”
That inconsistency is becoming the theme of her crop tour this year.
“Stands are better, but they’re much more variable than I remember them being in quite a few years, actually,” Anderson says.
Disease Pressure Down From 2024
Anderson conducts her own crop tour across Polk County each year, and this season one of the biggest surprises has been how little disease pressure has shown up, at least compared to last year.
“There’s quite a bit of disease moving into the upper canopy now,” Anderson says. “Again, this is a mature corn crop though, so this disease does not matter at this point for yield.”
Walking through one field, she points out the telltale signs.
“All these little pustules here and the little kind of yellowy brown spots , and then there’s a bit of tar spot as well,” Anderson says. “Those black spots are all the tar spots.”
Even so, she says this year’s disease load is nowhere close to what she saw in 2024.
“This is nothing like last year. So a field like this last year would have been completely covered with the southern rust probably three weeks ago,” says Anderson.
Early-Season Rain Still Leaving Scars
While the lighter disease pressure has been a pleasant surprise across Iowa fields this week, many central Iowa fields still can’t escape the scars left by too much rain earlier in the season.
“You go in and out of wet areas, and then not only that, but within a stand count you may have, 32,000 or 33,000 plants,” Anderson says. “But as you go through, there’s more small ears. And so it is a harvestable ear, but it’s a significantly smaller ear than those surrounding it.”
Two ears Anderson pulled from the same county illustrate just how big a difference a few inches of rain can make.
“You can clearly tell when there was too much rain,” Anderson says. “If you look, just the size of the ears compared with the size of the ears we’re pulling out of this field. It’s just a substantial difference.”
The gap comes down to how much rain each field received in late June and early July.
“The one on the right was from kind of northeast of Elkhart, probably in an area that during that time frame would have gotten anywhere from maybe 8 to 12 inches of rainfall in about 36 hours,” Anderson says. “And this one over here would have been probably more in the 5-inch range in that same time, and the ground sloughed the water significantly better than this did.”
That timing of the heavy rainfall made the damage worse, Anderson says.
“In our case here in central Iowa, in that particular area in Polk County, that was a really problematic timing, right ahead of the Fourth of July, right ahead of tasseling for most of these fields. So in this field, I had to walk a substantial distance to even get to corn that was producing ears,” Anderson adds.
Despite the variability, Anderson remains optimistic about the crop’s overall potential.
“I think we are going to have some really good corn,” she says. “It’s just going to be really variable as to where you’re located at.”
A Resurgence of Crown Rot
Alongside the variability, Anderson is also flagging a disease she says is making a comeback after several dry years: crown rot.
Walking past stalks in various stages of decline, she notes the range of severity. “I mean, most of them have some kind of an ear on them,” Anderson says. “They do vary a bit as to how far along they were when it died.”
As she spots crown rot in several fields,s he says the damage to some stalks are further along than others.
“I’ve seen some that are like really rubbery — this one is pretty solid, so it must not have died all that long ago,” Anderson says of one stalk. Of another, she says simply, “It’s totally hollow.”
Anderson says crown rot had largely faded from view in recent years, but conditions this season have brought it roaring back.
“Probably like four or five years ago is when I would start to notice it, but it would be so rare. I don’t know if that’s just because we went through 2020 to 2024, basically, we would be considered in drought that whole time, and it was so dry. And so now we’re getting sufficient to excessive rainfall, and we’re seeing a lot more of it,” she adds.
But she says the fact it’s showing up as widely as it is this year, is causing concern.
“It’s almost like we’re having this big resurgence of it,” she adds. “I don’t know what the exact cause of that is, but it’s clear that it has some type of genetic component, and then it’s environmental.”
Anderson says the oversaturated soils at the start of summer likely infected plants early, even though symptoms didn’t show up until much later in the season.
“From a time frame this year, probably early August is when I started to notice it,” Anderson says. “In some cases you could see these sort of — we call them like the ghosted plants — where they have almost like a gray-green color, very dried out, amongst totally healthy plants.”
The scale of it, though, is what’s caught her off guard.
“I know it’s an old thing, but it seems relatively new again, because we went a really long time without seeing much of it,” Anderson says. Asked if she’d ever seen crown rot this bad, her answer was direct: “Not as bad as this year. This is substantial.”
An Uncertain Yield Impact
Even with visibly rotted crowns, some of those stalks are still holding sizable ears — which makes pinning down a yield impact difficult, Anderson says.
“I don’t think you can, and I don’t know that anybody ever will be able to, because it’s one plant out of 100, it’s one out of 500 plants, how are you ever really going to pick that up on a yield monitor? I would say that there’s substantial variability. A lot of those ghosted plants appear to be ones that were weak to start with. I pulled out some really nice, very healthy plants that have very rotted crowns,” says Anderson.
She says the plants struggling the most tend to share a common trait.
“The ones that seem to be taking the earliest seem to be kind of the later emergers, the ones that were struggling to start with,” Anderson says. “And so there’s going to be a wide range, even that impact within one field between a plant that died three weeks ago versus a plant that just died 10 days ago.”
Watching Stalks Closely Ahead of Harvest
Asked about the biggest negative surprise of her crop tour so far, Anderson doesn’t hesitate.
“The amount of variability in the ears and early death on some of these plants,” Anderson says. “I don’t want anybody to be taken by surprise by plants falling early. I think we are probably going to get started harvesting here by the end of this week.”
She’s urging growers to scout their fields closely as harvest approaches. “I think we need to keep an eye on these things, because it’s going to be a long harvest season, and making sure that we’re not taken by surprise by stuff falling before we get out to it,” Anderson says.
As for the biggest positive surprise?
“I have found some really big ears here,” Anderson says. “There’s some corn that looks really good.”
With harvest just days away, a big Iowa corn crop is still within reach. But the final yield will come down to how much this season’s variability took away.
