Illinois Crop Update – September 19, 2025
Steve Brand– Commercial Agriculture Specialist
DeKalb County
Soil Condition: Near Normal
We have had a bit of a mini heat wave here in the middle of September as temperatures returned to near normal compared to the previous two weeks of cooler weather. The warmer temperatures are helping the corn and soybeans progress along through maturity as we are a bit behind the rest of the state harvest and maturity-wise. As the rest of the state is entering into some more substantial droughts, north of I-80 is still well within normal rainfall with a small pocket up near Evanston entering into another early drought phase. With little rain in the forecast, I don’t expect many delays with dry down and senescence. Some windy days would help greatly as well. Disease has emerged in fields due to the cooler temperatures we have seen in prior weeks with heavy dews. Tar spot in corn mainly which will build inoculum for future seasons in fields that have hot spots, as well as SDS and Cercospora in soybeans. The SDS has done most of the damage it will do but the Cercospora can lead to purple seed stain and docks at the elevator, so that will be a disease to monitor throughout harvest.
Corn is firing up through the fields but there is still a lot of green out there. The furthest progressed fields I saw in Dekalb were just getting to black layer, with other fields still in the 60-75% milk line. This warmer and dry climate will help the plants to start to dry down in the next couple of weeks. West and south of Dekalb area are well ahead maturity-wise, and harvest will be here in a matter of weeks. Corn has strong stands, and I have not seen much if any lodging across the region outside of small pockets that had some hail damage early in the season.
Soybeans are turning and senescing rapidly. The late start to the season with cooler temperatures have prolonged the season quite a bit compared to other areas of northern Illinois. Cercospora is the main disease I have been seeing in scouting with a small amount of frogeye leaf spot. Beans are still very wet, and very few fields have reached near complete defoliation. Another week and a half and defoliation should be close to finished.
On more of a fun note, apple orchards and pumpkin patches are in full swing, and there are plenty of fun fall festivals on the horizon to enjoy this great weather we are having across northern Illinois!
Meagan Diss – Commercial Agriculture Specialist
Warren County
Soil Condition: Moderately Dry (soil is dry, plants may be browning or stressed, water bodies are low)
Harvest is here throughout the county and nearby counties. We are seeing the effects of little to no rainfall mixed with the hot temperatures from the past week being reflected in the low moisture in harvested crops. Some fields that were later planted aren’t quite ready yet but we’ll definitely see an uptick in harvest in the coming weeks as the weather has really been drying down crops. Now is a great time to double check harvest safety measures and ensure everyone knows what to do just in case.
Talon Becker – Commercial Agriculture Specialist
Vermilion County
Soil Condition: Moderately Dry (soil is dry, plants may be browning or stressed, water bodies are low)
Harvest is underway in southern Vermilion County. With the hot and dry weather we’ve had, most farmers seem to be focusing on soybeans at this time, likely in the hopes of minimizing shatter and header losses. I did see a number of corn fields harvested, but those consisted mostly of seed corn fields and only a couple production fields. Of the corn still standing, the majority is at R6 “black layer” but still with some green in the leaves of the upper canopy. I did find a couple fields still in early R5 “dent” yet to reach maturity, but those were few and far between. As has been the story for much of the region, ear sizes and tip fill have been relatively variable field to field, with some showing full ears and others an inch plus of bare cob. Soybean fields still standing were generally in the R7 “beginning maturity” to R8 “full maturity” stages, with a few stragglers still in the late R6 “full seed” stage.
