Nebraska Corn Yields Fall 20–30 Bushels as Tar Spot Hits Late

Nebraska field corn yields are running 20 to 30 bushels per acre below last season in the central Platte River Valley, even as USDA's October estimate for the state jumped to 188 bushels per acre — a projection that surprised analysts and sits at odds with what farmers are reporting from their combines.

Greg Greving, who farms with his sons Shane and Jeremy near Chapman, said disease pressure — including tar spot — has hit popcorn and field corn hard, leaning corn over and cutting yields across the board. Dust defines this harvest.

"In over 50 years, I've never seen the combines so dirty after working the fields," Greving said. "Normally, we would change the engine air filter once or twice per harvest, but this year, we've been changing it two or three times a day."

How far along is harvest?

USDA's National Agricultural Statistics Service put Nebraska's corn harvest at 37% complete on Oct. 19, a 10-point jump over the previous week but still behind the five-year average of 48%. The gap reflects the difficult conditions growers face in the field.

Is tar spot the whole story?

It is not, and the record shows why. Brandon Christiansen of Plainview expected tar spot early, as it arrived in 2025, but the disease struck late instead. "This year it came on later, and then at the end of the season, it just blew up," he said.

Nebraska Extension plant pathologist Tamra Jackson-Ziems, who scouted fields all summer through ScoutNebraska, a new weekly live in-field reporting platform, said the picture is more complicated than one pathogen.

"There is so much variation this year, field to field," she said. Heat and warm night temperatures early in the summer, followed by weeks of heavy cloud cover and high humidity, likely also cut yields. Some of the gray-to-black fungi alarming farmers on leaves is beneficial residue breakdown, not disease, she noted.

Other problems include:

• Corn kernels germinating inside tight husks under end-of-season moisture
• Ear rot, stalk rot and crown rot compromising stalk integrity
• Early plant shutdown and lodging under wind

Where standability is questionable, Jackson-Ziems advised, farmers should harvest those fields first. Fungicide timing, method and coverage made a measurable difference this year.

Where is tar spot heading?

For the first time, Jackson-Ziems observed tar spot in southwest Nebraska — a region where arid weather had kept it off farmers' radar. The disease, expanding from eastern Corn Belt states, is moving west and north across the state. "It is probably only a matter of time when it will be confirmed in eastern Colorado, too," she said.

What did fungicides return?

Christiansen sprayed twice this season, a little later than in 2025, using the most expensive products on the market. On his irrigated corn, treated fields beat check strips — "but not that much better," he conceded. His conclusion: high-yield Eastern farmers who spray several times a season point to Nebraska's future, but cheaper fungicides may suffice.

Late wind events leaned his best corn while poorer fields stood, he observed: "It seems that the best-yielding corn leaned over, and the poorer corn withstood the winds." He has ordered pickup attachments for his corn header; Greving called pickup reels a necessary tool this year.

Mother Nature set the ceiling, in Christiansen's view. Uneven emergence, an early drought, then a sopping-wet month limited the crop from the start — and irrigation itself feeds disease. "We are keeping the fields wet 24/7. We are going to have disease," he said.

His prescription is plain: keep the crop healthy all season, match genetics to the threat, and weigh the return on every input. Genetics research will eventually catch up with tar spot, he said, but unforeseen diseases and insects will take its place.