It’s a challenge to report on soil conditions in northeast Illinois due to isolated pop-up thunderstorms. Some fields received over an inch of rain, while many less fortunate areas are drying quickly under above-average temperatures. I’ve noted many soybean fields exhibiting significant leaf burn from post-herbicide applications—likely a result of tank mix chemistries, additives, and environmental conditions. As our day lengths shorten, we’re reminded that soybeans in our region have an indeterminate growth habit, meaning vegetative growth (additional leaves) continues even after reproductive growth (flowering) begins. Despite high temperatures and limited rainfall, most corn fields visited still have wet leaves early in the morning. Periods of leaf wetness and high relative humidity are key risk factors for several corn leaf diseases, including Tar spot and Gray leaf spot.

Recent precipitation in Northeast Illinois ranged from 1+ to over 4 inches of accumulated rainfall. Some edge-of-field wind damage was noted in corn fields. The earliest planted soybeans are starting to flower, entering the reproductive stage of the crop. The most mature corn has reached, or is near, V10 to V11.

A reminder: if scouting mature corn, lower leaves will start to drop. In these cases, the first measurable internodal space is generally between the 5th and 6th node. Recognizing this provides a starting point at V6 when staging older corn. Depending on corn hybrids, expect between 15 to 20 leaves prior to tassel emergence. This is an important period of rapid growth as the corn plant creates leaves and stalks to provide photosynthate for the ear and developing kernels.

I’m a strong advocate of spending time on the ground scouting fields and recognizing any manageable issues that may arise. That said, I can also appreciate drone imagery for providing different perspectives on the developing crop. I have had mixed experiences with drones, but I have to admit the newer generation is more user-friendly. For those with access, collecting aerial images as the soy and corn crops transition from vegetative to reproductive stages can provide insight during end-of-season crop evaluations.

Areas within the NE region are starting to dry but potential precipitation is forecast. Favorable higher daytime temperatures are helping both corn and soy, particularly no-till soy that had been lagging. Post herbicide applications and nitrogen sidedress operations continue. Several edge of field issues reported this week, including likely deer feeding on V6 corn and Canada thistle encroaching on soy field edges. Options are limited with deer feeding at this stage of the growing season, we can hope their diet shifts to something besides corn. The perennial Canada thistle can be a challenge to control in a crop setting. The weed can spread vegetatively by rhizomes and windblown seed. The best growing season time to treat Canada thistle with a foliar applied herbicide which can through the plant (systemic) is normally in June after the first flower buds are formed and before the first flowers open. One hundred percent control often requires multiple timed applications including a fall application.

A cool week ending with several warm days with consistent winds provided favorable first cutting hay-making weather. June 4th brought widespread precipitation across almost all of NE Illinois. Below average temperatures slowed crop growth, most apparent on no-till soy fields. Recent changes in weather patterns and welcome precipitation should accelerate growth. The regional soy crop ranges from emerging to V3. The majority of corn is V4 to V7. Yellowish corn that has yet to receive intended sidedress nitrogen is apparent. Why is nitrogen deficient corn yellow? The short answer is that nitrogen, including many other important processes, is required to produce chlorophyll used in photosynthesis; its chlorophyll that gives the corn its green color. The general consensus is to sidedress nitrogen before the corn reaches the period of rapid nitrogen uptake (V7-8 through pollination). The Nitrogen Management for Corn document authored by Dr. Emerson Nafziger shared that applying N as late as tasseling in severely N-deficient fields may increase yields, but the later the application, the more yield will be lost. Post corn herbicide applications have started when weather (including wind) has allowed. Producers are encouraged to evaluate both pre and post herbicide applications.

Below average temperatures this week have slowed crop growth. Most planting is complete and limited replant, mostly soy, has taken place. While most observations are focused on aboveground 2025 crop development, it is interesting to consider what is happening underground. While variation exists among hybrids and locations we can share several generalizations about corn root growth. The maximum rooting depth is largely determined by the depth of the groundwater table. Corn roots require oxygen to respire and survive, for this reason most corn root growth ceases once the water table (and saturated soil) is reached. Roots can be expected to extend or “meet” across 30-inch rows by the corn plant at V6 but has been reported in earlier stages in favorable growing conditions. The corn plants’ maximum root depth, which can reach six feet (if not limited by soil barriers) is normally attained by the blister or milk stage in the growing season. Maximum root depth can be helpful, but we are reminded that most of the root density is in the top two to three feet of the soil profile.
While scouting fields this week I am visually reminded of management suggestions shared by Extension Weed Specialists, including Dr. Aaron Hager, on the importance of preventing Waterhemp from reaching the stage of viable seed production. When allowed to do so, these prolific seed producing weeds can generate an impressive flush of weed seedlings the following year. Despite the cool week Burcucumber is getting an early start and has been noted as well. Evaluate stand and post herbicide efficacy in both corn and soy fields in the upcoming weeks.

Widespread precipitation this week in NE Illinois along with much cooler temperatures. Most planting is starting to wrap up in the region. I visited several soy fields that after an initial rain event went weeks without additional precipitation leading to emergence issues. When visiting the field after recent rains, some emergence is still taking place while other soy seedlings simply couldn’t push through the crusted soil. Soybeans have epigeal emergence which means the hypocotyl arch pulls the cotyledons through the soil surface. Crusted soil can make this a challenge. Finer textured soils with low organic matter that have limited residue are more prone to crust. Crusting is also more likely following a heavy rainfall event causing soil aggregates to move into the open pore space. Limited rainfall after the heavy rainfall event intensifies the chance for soil crusting. Soil crusting causes soybeans to use all their energy trying to emerge from the soil and can result in a poor stand. What soy population is needed before considering a replant? Dr. Emerson Nafziger addressed this issue for both corn and soy in a 2020 farmdocDaily posting https://farmdocdaily.illinois.edu/2020/05/replanting-corn-and-soybeans.html . In his article Dr. Nafziger shared an adage for soybean stands, ” When plants are easy to count without bending over, there aren’t enough of them”. While we are cognizant of lower soy population’s remarkable ability to compensate yield, growers are still encouraged to scout fields that are prone to crusting or emergence issues for adequate stands. NE Illinois alfalfa fields are starting to blossom, I expect the season’s first cuttings to take place as soon as window of favorable weather for drying and harvest takes place.

A busy planting week for most in NE Illinois. Above average temperatures this week provided several days accumulating at least 17 GDU’s (base 50) per day. The favorable conditions for germination and seedling growth also extended to several problematic weeds including Waterhemp and Marestail. Early recognition of these and other weed species is important because post management strategies become challenging as the weeds reach critical sizes. Several areas missed recent precipitation events and we have received reports of disappointing soy stands in earlier planted fields. Growers are encouraged to evaluate crop emergence to determine if replant is a viable option.

Planting has resumed in Northeast Illinois after recent precipitation. Nearly ideal field conditions early to mid-April allowed for an early start to the planting season. Windshield surveys suggest a growing number of area farmers planted some, if not all, soy before corn. Corn that emerged are demonstrating a yellowish cast, the result of earlier cloudy and cool days. A reminder that seedling corn is still largely dependent upon kernel reserves. Once corn reaches the V3 growth stage, seedlings begin the transition to being dependent upon the nodal root system. The cure for the discolored corn, warmer and more cloudless days. For those with alfalfa, just as last year, alfalfa weevil is prevalent in area fields. If the alfalfa has reached 16 inches in height, taking the first cutting is often the preferred management tool for the pest over an insecticide application. Harvesting the alfalfa removes food and shelter and exposes larvae to harmful UV rays. Regrowth in heavily populated weevil fields should be monitored.

A widespread rainfall event passed through northeast Illinois putting a temporary hold on harvest activities. This pause gives growers the opportunity to visit fields and evaluate combine performance in harvested areas. This is also one of the easiest times to measure harvest populations in corn fields. For 30-inch rows, count the number of plants in 17 feet 5 inches and multiply by 1000 to determine population per acre. Winter annuals have started to grow, including common chickweed and henbit in northeast fields. Several reports of soy as dry as 9 percent moisture have been shared. The following recommendations originated from the University of Nebraska in reference to soybean harvest, “moisture content can increase by several points with an overnight dew or it can decrease by several points during a day with low humidity and windy conditions. Avoid harvesting when beans are driest, such as on hot afternoons, to maintain moisture and reduce shattering losses. Harvesting immediately after a rain, if field conditions allow, will result in higher moisture contents. However, several wetting and drying cycles from rain events will make the soybeans more susceptible to shatter losses from pods splitting open.” The full UNL article for equipment adjustment for harvesting soybean can be accessed at https://cropwatch.unl.edu/2017/tips-harvesting-soybeans-13-15-moisture

The growing season and grain fill is all but over for most and has ended on a dry note. All fields I have visited have been tinder dry, as harvest gets underway a reminder to check fire extinguishers and if available, have a tractor hooked to a tillage implement ready to go to help contain a field fire. Checking combines for residue buildup throughout the day and having the local fire department phone number readily available is also recommended. Despite Tar Spot getting a later start in Northeast Illinois, by late August and September it spread throughout the upper corn canopy reflected by image provided. Final yields will share the effect Tar spot and drought had on the 2024 crop. While checking corn fields I am finding very limited olive-green ear rot symptoms. This can be representative of Penicillium ear rot or Aspergillus ear rot. Aspergillus is most favored by hot and dry conditions. Aspergillus ear rot appears most commonly at the tip of the ear but can be scattered throughout. This ear rot is particularly troublesome because of their ability to produce a mycotoxin called aflatoxin. A great resource for identifying and understanding ear rots can be found from the Crop Protection Network. https://cropprotectionnetwork.org/publications/an-overview-of-ear-rots
Wishing a safe harvest to all!