Warmer weather, diseases and less rainfall could impact Nebraska’s corn harvest

Drought has slightly loosened its grip compared to earlier this year, when wildfires scorched the little remaining grass left in western and central Nebraska. But one of Nebraska’s most profitable cash crops still looks like it’s struggling as harvest approaches.

In the latest drought update from the National Drought Mitigation Center, about 3% of the state, all in Nebraska’s Panhandle, remains in exceptional drought – the worst classification on the NDMC’s scale. But a quarter of the state is experiencing extreme drought, and that’s persisting from the Panhandle through central Nebraska and even the northeastern edge of the state. While the southeast has seen improvement this summer, it saw slight increases in drought within the last week, but recent rains this week and some showers expected in the coming week could improve conditions.

Nebraska’s corn crop is not expected to be as poor as its wheat harvest, which appears to be on track for one of the worst in history and led many wheat farmers to abandon their fields altogether. But ag experts are keeping their eyes on a few issues that could impact the last half of this growing season.

Decent weather conditions throughout the Corn Belt this year are putting most states on track for a regular harvest, except for parts of Nebraska where warmer weather and a lack of rainfall have some researchers expecting lower yields than average.

University of Nebraska-Lincoln researchers observed a temperature anomaly this summer in Nebraska where nighttime temperatures averaged about three degrees warmer than normal. That could mean irrigated crop acres in southeastern Nebraska see lower yields than normal, according to UNL’s mid-July outlook.

Along with an increase in warmer nighttime temps, Nebraska and much of the Midwest is seeing a slight increase in dewpoints, according to Eric Hunt, an agricultural meteorologist.

“We are about one to two [degrees] Celsius above the second half of the 20th Century in terms of dew point,” Hunt said in a recent drought outlook update at UNL. “As this planet warms, it could hold more water vapor with warmer Gulf temperatures. We are basically seeing the effect of that east of the Rockies.”

And while some more moisture in the air might sound beneficial, it could bring a better breeding ground for diseases that can limit a crop field’s yield.

“I think one of the reasons we have been dealing with more issues with these fungal diseases is probably, flatly because we’re getting more humid here in the summer,” Hunt said.

One of those diseases has already arrived in Nebraska: tar spot, a relatively new problem for Nebraska farmers.

“The fungus has only moved into Nebraska in about 2021,” Extension Plant Pathologist Tamra Jackson-Ziems said. “It can be very bad when you know you have very favorable weather conditions, and on hybrids – some of them will be more sensitive than others. In the worst-case scenarios, they have documented 50-bushel yield loss. So, imagine 50 bushels less when you were expecting 150 to 200, and so it can have a big, big impact.”

It’s an issue that presents itself on the leaves of corn, and when there’s a lot of the disease, it covers larger portions of the leaves. That can really inhibit the plant’s ability to fill grain, Jackson-Ziems said.

“So the ultimate cost of that is that farmers don’t get as much corn, or the total overall yield that they get is less – means their income is less, and that’s what we’re trying to prevent,” Jackson-Ziems said.

More than two dozen counties in Nebraska have confirmed cases of tar spot, but the state’s recent 100-degree weather could slow its spread. Tar spot can overwinter in Nebraska, making it a recurring guest for farms that experienced it last year.

Corn farmers are also keeping their eyes out for southern rust, another corn disease. No cases have been confirmed in Nebraska, but confirmed reports have popped up on farms in southern Kansas, Missouri and eastern Iowa. It wreaked havoc on farms last year. And it dealt a blow to some farmers who had it two years in a row.

“To have some southern rust is not unusual, but it was bad two years in a row, and it’s created a lot of – almost – trauma in people because it got worse than they expected and impacted yields, and it was a bigger issue too because of low commodity prices,” Jackson-Ziems said.