Prolific precipitation and high late-summer heat is speeding crops to maturity.
"So be ready to harvest not by the calendar, but by the crop," said Cody Hornaday, a technical agronomist with Koch Agronomic Services.
"Parts of northern Illinois and northern Indiana got absolutely hammered a couple weeks ago, with record rainfall in a lot of places," Hornaday said at last week's Farm Progress Show. "But I think the biggest thing that basically sticks out across the entire [Midwest] region is the heat."
Hornaday ran a growing degree unit calculation starting March 1 through the end of August in southern Indiana.
"Based on that information, we were within 50 GDUs of the highest level of GDU accumulation on record," he said.
Just as across most areas of the Midwest, high nighttime temperatures drove a lot of the GDU calculation, Hornaday added.
Abundant rainfall has helped the crop deal with this, he said.
"But the heat has really accelerated development," Hornaday noted. "In southern Indiana and part of Kentucky, farmers are a good week to two weeks ahead on harvest right now, with some farmers starting as early as two weeks ago."
Variability's the story
Weather variability also has been part of this year's crop production story.
"There have been areas with too much rain and [areas with] not enough rain," said Stefan Swenson, Syngenta corn product manager.
The good news is that compared with 2025, disease has not been as severe across the Midwest. Still, don't let down your guard come harvest. Early prolific precipitation spurred nitrogen losses, while later-season rainfall could fuel fusarium crown rot.
Both could result in standability problems and lodging losses at harvest, so target these fields for harvest first.
"By and large, there are diseases [such as fusarium crown rot] that aren't as visual as southern rust last year," Swenson said. "These diseases can impact late-season standability that you cannot now visually see but will be apparent at harvest. Now is a good time to go out and scout fields, dig up roots and cut open stalks to see if there is any rot occurring."
Variability extends to weeds
Variability also affected soybean weed control this year.
"Some fields are really clean, while other fields are starting to get a little hairy," said Sam Breckenridge, a Helena Agri-Enterprises product manager.
Why the difference?
Fields that received layered residual herbicides with multiple modes of action best controlled weeds such as waterhemp. It continues to emerge late into the season, and August rainfall can accelerate this tendency.
"Waterhemp is aggressive and can pop through that [soybean] canopy," said Jim Talbert, a product specialist for Helena Agri-Enterprise.
This also applies to Palmer amaranth. Like waterhemp, this pigweed - present in Midwestern states such as Iowa - resists several herbicide modes of action.
"Overlapping residuals that stop them before they start is the best strategy for managing them," Talbert said. "Once they take off, they grow so aggressively that you can't outpace them with just a postemergence [herbicide] application."
