Illinois Crop Update – September 5, 2025
Steve Brand– Commercial Agriculture Specialist
DeKalb County
Soil Condition: Near Normal
Cooler temperatures have arrived this fall (late summer really) as we move through the waiting period of the growing season for corn and soybeans. Temperature averages in the 70s and low 80s have brought much relief after a very hot stretch across Northern IL. Nearly every corner of Illinois north of I-80 is at normal rain and water levels as down state begins to enter into a slight drought, and plants continue to work through ear and pod fill. I have noticed diseases starting to really ramp up with temperatures dropping and heavy dews every morning.
Corn is still green and starting to fire as it reaches maturity. Most fields I visited were full dent with the milk line in the ear around 50%, maybe a little further along in some places. (West of Dekalb was scouted this week). With the cooler temperatures and daily dews, tar spot and ear mold in particular have taken off in corn. Every field I visited had lesions well into the upper canopy with lower leaves turning a brown necrotic and dying. The upper 1/3 of plants above the ear are still green so ear fill is still occurring even as the bottom dies out. Ears are starting to see small amounts of mold on the ear tips as well. Black layer is most likely 10-14 days away based on the milk line and cooler temperatures.
Soybeans are still mostly green with select fields either planted early or an earlier variety starting to turn and enter senescence. For as disease free as we were early in the season, SDS has flared up across many fields and is starting to take off in hot pockets of fields. This year is a very important year to scout your fields if you see SDS symptoms. Red Crown Rot is a new disease seen in the area that has the exact same foliar symptoms, and is treated with different seed treatments if it is found in your field. The key characteristic to look for is a bright red color on the soybean stem just above the soil layer, and in some cases red spore balls called perithecia. If you find what you think could be red crown rot please contact your local extension office and we can work with you to get that sample tested for identification.
Other than that we are moving along and marching towards harvest. NW Illinois and Joliet are a bit ahead of the Dekalb area in terms of maturity and harvest will be right around the corner!
Doug Gucker – Local Food Systems and Small Farms Educator
Dewitt, Macon, and Piatt County
Soil Conditions: Moderately Dry (soil is dry, plants may be browning or stressed, water bodies are low)
The past two weeks have seen late-season leaf diseases appear in area fields: Tar Spot, Rusts- Common and Southern, Gray Leaf Spot, etc. A few farmers have taken out end rows in corn fields. In moderate drought areas, corn fields have fired up to ear in the drier parts of the fields. Corn fields are in the Dent stage, R5, and a few fields are in the Mature stage, R6.
Soybean fields are turning yellow, reaching the R7, Beginning Maturity stage, with early maturity soybean fields at or nearly at the Full Maturity stage, R8.
Talon Becker – Commercial Agriculture Specialist
Douglas County
Soil Condition: Mildly Dry (soil is drier than normal, plant growth may have slowed)
The storms that moved through the area in the evening of 9/3 did brought some needed rain, but rainfall totals appeared to be variable across Douglas County based on field soil conditions during my survey. This is backed up by the difference in registered rainfall totals between the Illinois State Water Survey monitoring stations in Bondville and Champaign, which recorded about 0.4″ and 1″ of rain, respectively, despite the stations being <10 miles from each other. In Douglas County, it appeared much of that rain missed the southwest part of the county.
Despite the dry conditions, corn and soybean crops are still looking good overall. Corn fields were generally in the early to mid-R5 “dent” stage. Tip fill was generally good, although ear size did vary a decent amount from field to field. Early maturity soybeans are starting to hit R7 “beginning maturity” in areas of those fields, but there are still plenty of later maturity soybean fields in the R6 “full seed” stage with a full green canopy. It seems harvest is still at least a couple weeks out for most in Douglas County.
