Published on September 4, 2026 7:35 am
Last Updated on September 4, 2026 8:29 am
by Rhiannon Branch FarmWeek
A stretch of high temperatures the first week of September, reaching triple digits in some areas of the state, accelerated dry down for corn and soybeans nearing harvest.
“We were creeping ahead on growing degree days, but this heat is going to put the finishing touch on some of this corn,” Dana Harder, field agronomist for Burrus Seed in western Illinois, told FarmWeek. “It’s going to expedite harvest.”
Harder said during the final week of August, corn lost about 6 percentage points of moisture. And, during the first week of September, the crop was losing a little more than 1 percentage point per day.
Planting dates in his coverage area were delayed by spring rains, but harvest start dates could be four to seven days ahead of average.
Reports of harvest progress and initial yields are already coming in from southern Illinois.
FarmWeek CropWatcher Melissa Williams began harvesting corn in White County Aug. 27.
“This is our first year with all white corn and we’re obviously not expecting it to yield the same as yellow, but so far it’s really surprised us,” she told Collin Schopp with the RFD Radio Network.
USDA reported 11% of Illinois corn was mature with the same percentage of soybeans dropping leaves as of Aug. 30. The department intends to publish its first harvest progress estimate Sep. 8.
Harder said corn in his area experienced nitrogen loss from excessive rainfall in June which is showing up now in the form of tip back and aborted kernels. Crown rot is also a late season concern.
“When we have a lot of moisture during the season, we can have some of that infection take place,” he said. “The additional stress during grain fill can make the stalk weaker, so you’re seeing some premature death out there and I think evaluating stock quality is going to be key going into this harvest.”
August rains likely helped soybeans but the heat wave may have robbed some yield from later maturing fields.
At the end of August, USDA rated the condition of the Illinois soybean crop 13% excellent, 46% good, 29% fair, 7% poor and 5% very poor while corn was considered 12% excellent, 46% good, 30%, fair, 8% poor and 4% very poor.
The national good to excellent rating for soybeans, at 58%, was down 2 percentage points from the week prior, making it the fourth consecutive weekly decline and the lowest rating for the week in three years.
