Illinois Crop Update – August 15, 2025
Russ Higgins – Commercial Agriculture Educator
Grundy County
Soil Conditions: Mildly Dry (soil is drier than normal, plant growth may have slowed)
This week Dr. Giovani Preza Fontes, assistant professor and Agronomy Extension Specialist from the University of Illinois visited the Grundy-Kendall County area and met with area producers where he shared expectations of both state and local yields. Farmers were provided with recent weather data and were encouraged to take kernel and population counts to determine yield estimates in their own fields. The pattern of variable rainfall and pop-up isolated thunderstorms discussed was demonstrated that day with rainfall ranging from 0 to 2 plus inches within a 40-mile radius. Most corn is at R5 and the likelihood of a return on investment on a fungicide treatment (or additional treatment) at this stage is unlikely. That said, scouting corn that did not receive a fungicide treatment in some fields is an introductory course in plant pathology. Symptoms of Tar Spot, Northern Corn Leaf Blight, Gray Leaf Spot and Southern Rust can all be found. Recent environmental conditions have been especially favorable for the development and spread of Southern Rust. All leaf diseases are reducing photosynthetic leaf tissue that would aid in grain fill.
Talon Becker – Commercial Agriculture Specialist
Iroquois County
Soil Condition: Near Normal
This week’s survey in the southern half of Iroquois County showed good crop conditions overall, but with some variability across the surveyed region. At the time of this survey (8/12), overnight rains in much of the area had replenished topsoil moisture in most fields surveyed. However, soil cracking and tip dieback in corn was found in several fields surveyed. Corn fields surveyed tended to be in R4 “dough” to early R5 “dent” stages. About a third of the fields surveyed showed an inch or more of tip dieback, presumably due to moisture stress due to soil conditions in the field and a lack of evidence of N stress in the plant canopies. Signs of foliar disease were minimal in corn. Soybean fields surveyed tended to be in the R4 “full pod” to R5 “beginning seed” stages. Plant health looked good overall, but some fields showed areas of stunted growth and a lighter canopy color. At this stage in the disease progression, observed symptoms did not provide a clear diagnosis. If you are seeing this in your field, submitting samples to the Plant Clinic (https://extension.illinois.edu/plant-clinic) can help with early diagnosis.
Reagan Tibbs – Commercial Agriculture Educator
Logan County
Soil Condition: Near Normal
Despite the seasonally warm temperatures during the last week, many crops across Logan County benefited from a rain shower early in the week. Most of the county saw 1 to 2″ of rain, which will undoubtedly help crop growth. Many corn fields are moving into the R5 “dent” stage, with not that many lagging behind the leaders. Much of the same can be said for soybeans, with most fields in the R5 seed stage.
Doug Gucker – Local Food Systems and Small Farms Educator
Dewitt, Macon, and Piatt County
Soil Conditions: Mildly Dry (soil is drier than normal, plant growth may have slowed)
Soil moisture conditions across the 3 counties vary from Wet to Moderate Drought. Rainfall has been quite variable across this area. Soybeans planted in April are in the R5 stage, Full Pod. The April-planted corn is in the R4 or R5 stage. Crops look good even in the dry areas at this time.
Weed control has been very good. I have noticed that the soybean fields conventionally farmed with weed issues typically only have a problem with one weed group, either the Amaranthus family or the Velvetleaf (Abutilon theophrasti). Grassy weeds have not been an issue across the area in conventional farmed fields.
