A very active weather pattern across northeast Illinois that spawned tornados, a derecho, and significant rainfall and flooding across the region. In corn fields, foliar leaf diseases are now more easily detected, including Southern rust. A Southern rust report was received by Dr. Boris Cameletti, University of Illinois Plant pathologist on July 23rd in Williamson County in southern Illinois. While the presence of the disease in not good news for northeast Illinois cornfields, the fact that it has appeared later in the season when compared to recent years is good news. With much of the corn crop now at R4 or dough stage, the benefit of a fungicide application, unless exhibiting severe pressure, is low. By comparison, in Grundy County Southern rust made it appearance by mid-July in 2024 and 2025. R4 is one of the shortest reproductive stages in corn plant development before reaching R5 or Dent stage. In fields where scouting has included the pulling of ears, we are finding along with neighboring states, incomplete or scattered kernel set on some ears. Suggested causes include temperature and moisture extremes during pollination, lack of wind during pollen shed, and hybrid characteristics. We are encouraging growers to check variations or responses between hybrids. Yesterday Dr. Conner Sible and Steve Brand from the University of Illinois visited with local producers as guests of the Kendall-Grundy Farm Bureau and local Illinois Extension offices in Kendall County and shared their growing season observations along with nutrient use and crop genetic (root structure) interactions.

As we progress through the second half of the growing season for corn and soy, conditions have been mostly favorable for grain fill in the Northeast region. Most soy is at or near R5 also known as the beginning seed or beginning bean stage. As rapid seed fill begins later in this stage, the soy plant starts to remobilize nutrients from leaves and stems to meet the demand of pod fill. In fields visited, disease and insect pressure in the soy crop has remained very low. I have not come across red crown rot in soy fields visited, but reports have this emerging disease spreading in Illinois. It was announced this week that Illinois farmers can receive free red crown rot (RCR) testing thanks to the United Soybean Board and the Illinois Soybean Checkoff in partnership with the University of Illinois. If you suspect that you have RCR in your fields and would like confirmation, please consider sending diseased samples to the University of Illinois Plant Clinic in Urbana. While scouting R3 or milk stage corn, I noted white frass on a developing ear, almost always an indication of feeding by the corn earworm. The corn earworm is also known as the cotton bollworm and is a pest of several crops in addition to corn and cotton. The adult female corn earworm moth prefers to lay eggs on fresh silk. The hatched larvae follow the silk to the tip of the ear where they feed and produce excrement or “frass”. Larva inside the ear do not have effective insecticide control. While this pest is a challenging insect to control in sweet corn operations, it usually is a minor concern in yellow dent corn. As we diligently continue our foliar corn disease scouting, a slight uptick in gray leaf spot was noted, but fields I have visited are remarkably disease free at this stage compared to recent years.

This past week saw hail, substantial rain, and missed opportunities for needed precipitation in varying fields across the northeast region of Illinois. Corn has reached R3 or the milk stage in the field I have been scouting this summer. At this stage the kernel no longer adds new cells to the kernel endosperm but fills the existing cells with liquid starch. If punctured the liquid or “milk” will spray or shoot out of the kernel. Foliar disease pressure in this field continues to be low, I have noted very sporadic purplish lesions in leaf midribs and on corn stalks. This is symptomatic of the fungal disease Physoderma brown spot. Especially on lighter soils or areas where significant nitrogen loss occurred, likely due in part to extreme rainfall, considerable remobilization of carbohydrates is taking place as corn plants cannibalize lower leaves to meet their nutritional needs of ear development. Soy has reached R4 or full pod stage, the beginning of a critical stress response period for the soy plant. New flower growth slows and plants lose their ability to remake new flowers and pods. Similar to the corn crop, disease and insect pressure currently are low in the 2026 soy fields I have visited.

A favorable week for crop growth in the northeast region of Illinois. Corn is pollinating, despite predicted 90 degrees plus highs this week, most fields have adequate moisture and should not suffer despite elevated temperatures at this critical stage for the corn crop. I enjoy my early morning coffee looking across several corn and soy fields. This past week I noted most mornings start with a mist or fog. The mist does not come directly from the corn and soy crops, even though both put water vapor in the air through the process of transpiration. The morning mist is the result of the cooling of the moist air. As the air cools overnight, it reaches its “dew point” and can no longer hold water as a gas, causing water vapor in the air to turn into liquid droplets. Of significance to those scouting for crop diseases, the morning mist extends periods of leaf wetness, a favorable requirement to several fungal leaf diseases. This week, with the appearance of brace roots in the corn crop, the question of underground root expansion was raised. There are many limiting factors to root growth, too much or limited moisture, soil compaction or other natural barriers. However, the general suggestion is that root expansion in the corn crop continues through pollination. At this point the crop redirects energy toward grain fill. By this time with favorable soil structure, it is not uncommon for corn roots to extend to six feet in depth. Our soy plants tend to generate roots further into the vegetative stages, to R5 and R6, beginning and full seed.
The corn crop is R1 with kernel fertilization underway. Soy is between R2, full flower and R3, or beginning pod. Despite favorable conditions for leaf diseases, I have yet to see an outbreak of tar spot on corn or soy leaf disease in fields I have scouted. Growers are encouraged to remain diligent with both field visits and local reports.

This week farmland in the northeast region received additional precipitation and winds over the July 4th weekend. Rainfall totals reported ranged from 1+ inches to isolated fields that received 9+ inches. When sharing an update, the challenge is whether to report on the part of the field that has been unaffected (or even enhanced) by the rainfall, or the parts of the field that have been killed or damaged by ponding or saturated soils. Depending upon where you look, there are outstanding portions of fields, but if you evaluate the field as a whole and note the unevenness and drowned out areas the field overall rating diminishes. Soybean are at R2 or full flower, at this stage the plants begin a period of rapid dry matter and nutrient accumulation. This week shorter season or earlier planted corn hybrids have reached R1 or pollination and scouting for foliar leaf diseases has intensified. This job will soon be less pleasant when pollen shed increases. In fields scouted, I have yet to find symptoms of Tar Spot. I have noted black specks on corn leaves, but the Tar Spot stromata (lesions) cannot be brushed off. What I have found are either wind deposited dirt or possibly insect frass or excrement. If you can wipe off the black spot on a leaf it is not Tar Spot. Follow our weekly reports for updates on Gray Leaf Spot, Tar Spot, Southern Rust and other diseases found in both corn and soy across the state.

In a recent report, I stated that warmer weather would benefit the 2026 crop, perhaps in the future I should qualify my term of “warmer weather”. A week of 90 degree plus days in Northeastern Illinois has allowed farmers and agribusiness the opportunity to play catch-up applying post herbicides. Last week, you could not travel a rural road without meeting a sprayer. Most fields have weed populations that have easily exceeded weed size management recommendations and most have drowned out areas that will likely germinate later season weeds. Fields this year are unlikely to have “perfect” weed control. Growers are encouraged to evaluate post herbicide applications and start scouting for leaf diseases in corn. Tar spot symptoms have been reported in the state, and one tool that can be utilized to see if a crop disease has been reported in your area is visiting the Crop Lookout Website. Crop Lookout is a real-time, interactive map that highlights emerging field crop issues across the United States and Canada. Updated throughout the growing season by university Extension specialists and research partners, the tool visualizes reports of diseases, pests, and other agronomic challenges as they develop. Northern Corn Leaf Blight or Goss’s wilt have been found in Grundy County as the crop is near the Tassel stage.

Another week with precipitation, in many areas ground sprayers have been unable to operate since June 7th. Many fields that are inherently poorly drained are ponded and both corn and soy are suffering. Farmers are facing the challenge of post applications of herbicide for corn and soy, and in some cases nitrogen for the corn crop. Warmer and dryer weather is desperately needed for the crops in the area. Most soy in the area not stressed by saturated soil has reached R2 (full flower), corn has reached V11. Waterhemp has reached 18 to 24 inches in untreated fields. Area alfalfa fields are flowering and Japanese Beetle have emerged in Northeast Illinois.

When I left Illinois for a brief vacation the first week of June, the Northeast Region was dealing with impending drought concerns (note wrapped corn from June 4th). Twelve days and 5+ inches of precipitation for many acres, an entirely new set of concerns for the 2026 crop. New concerns relate to saturated soils, erosion and crop damage caused by moving surface water and wind, and the lack of opportunity to apply post herbicides while weeds are in the optimum treatment window. Even when standing water dissipates, a saturated soil very quickly limits oxygen availability to a growing crop. An oversimplified way of describing the effects of a saturated soil is that the lack of soil oxygen available to the roots can reduce or stop plant functions. This can include transpiration, nutrient uptake, and water uptake. Extended saturated soil can cause visible stunting and even plant death, resulting in varying degrees of reduced final yield. In addition to struggling crops, persistent precipitation has prevented many post-herbicide applications from taking place. A few weeds, especially waterhemp, easily have exceeded the recommended maximum weed size for control of most herbicide. Soy on well drained soils are starting to enter their reproductive stage (flowering). We are near halfway through the growing season and have experienced the environmental conditions of excessively cool, hot, dry, and wet; What’s next?

A dry week in the Northeast region, corn picked up one additional leaf (V6) and soy pushed out another trifoliate (now V2) in the fields that I am observing on a weekly basis. Hay harvest, nitrogen sidedressing, and post herbicide applications are all taking place. With the comparatively quick onset of dry conditions and stress on both crops and weeds, farmers are encouraged to evaluate post herbicide applications at least a week after application. Environmental stress, including drought, can slow active growth and herbicide solution absorption in plants, decreasing herbicide effectiveness on targeted weeds.

A warm and mostly dry week for growing crops (and weeds). Several mid to high eighty-degree days pushed corn from V3 last week to V5. At V5, all of the embryonic leaves and ears have been initiated in the corn plant, and its growing point (meristem) will soon be above ground. The warm weather also pushed the soy crop, last week a no-till soy field at VE has reached nearly V1 with the first set of trifoliates unfurling. I would be remiss if I did not share that the great growing weather also benefitted weeds as well. Several species, especially waterhemp are matching the crops quickened growth. In this region, most planting has finished and farmers are taking advantage of the rain free forecast to harvest the first hay cutting.
Over the years I have made numerous trips from Grundy County to the University of Illinois campus. My most frequent route includes a stretch of Route 47 straight south to Interstate 74. Yesterday I made the trip and wanted to share my windshield observations. I noted several agronomy practices that seem to be picking up in frequency, they include sidedressing corn with liquid nitrogen, no-tilling soy into a standing cereal rye cover crop, and a growing number of winter wheat acres in rotation. It will be interesting to follow these fields and practices as the growing season progresses.