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!

The 2024 growing season is ending on the dry side in Northeast Illinois. Aerial cover crop seed application has started, but limited harvest activity has taken place in the region. I continue to be surprised at the difference in maturity and color of crops across and within fields. From plants ready to harvest, to those mostly green from top to bottom. This was very apparent at the University of Illinois Soybean Variety Testing plot near DeKalb. Late season disease symptoms showing up in soy include SDS (to be confirmed by the plant clinic). Looking at corn ears, we see smaller kernels in areas effected by late season drought, the impact on final yield will be determined soon at harvest.

Another dry week, in travels across northeast Illinois we see both green corn and soy fields and in others, plants that have browned, dropped leaves and are likely only weeks from harvest. We have had reports of hand shelled corn samples near 30% moisture. For areas that had heavier soils, received timely rains and had higher water holding capacity, the yields will be impressive. A visit to the Sandwich Fair this week judging corn entries demonstrated sizeable ears. If they are representative, it will be interesting to see final yields from these locations. Somewhat of a surprise, we are finding pockets of white mold in some soy. Even though the symptoms (dead plants) are easily visible now, the initial infection took place when the soy was in the R1 to R3 stage. Harvesting white mold infected soy last and then cleaning your combine can limit the spread of sclerotia, the overwintering structures of this disease, to other areas or fields. Tar spot continues it spread in corn, even in earlier fungicide treated fields.

The past three days featured almost unbearable 90 degree plus days, compounding extreme dry or drought conditions for the 2024 crop. It ended with a 1 inch plus rainfall for some in the Northeast on Tuesday night. Prior to the precipitation, both corn and soy were demonstrating heat stress. One of the oddities found while scouting our now mostly R6 (full seed) soy was Thistle Caterpillar. The Lepidoptera adult is also known as the Painted Lady Butterfly. Thistle caterpillars are not known to overwinter in Illinois but migrate north annually from the southern US and Mexico. The caterpillars form webs by tying leaves together with silk creating a protected area for them to feed. Almost always considered a sporadic pest, it rarely causes enough defoliation to warrant treatment.
Today, Dr. Boris Camiletti, Plant pathologist with the University of Illinois shared his observations on the 2024 growing season from a plant disease standpoint to a gathering of Northeastern Illinois farmers. Diseased crop samples brought to the meeting were identified as Tar Spot, Northern Corn Leaf Blight, Gray Leaf Spot, Southern Rust and White Mold. In addition, ear rots Fusarium and Penicillium were found. Dr. Camilletti encouraged growers to continue scouting practices to aid in management decisions, make use of the Illinois Plant Clinic, and be on the watch for Red Crown Rot in soy that it is progressing its way north in the state.

Recent precipitation and current cool conditions are favorable for both corn and soy crop grain fill. The extended forecast is dry and warmer, which could expedite the grain fill window. For crops on some lighter soils in the Northeast, recent rains appear to have arrived late. Corn in sandy and soils with poor water holding capacity senesced quickly over the recent week. In field areas that flooded or have decreased plant populations due to environmental conditions, I’m finding grass weeds happily filling the void. One species in particular, Fall panicum, seems to be having an exceptional year. This summer annual can reach seven feet in height and is recognized by appearing to be growing in a zig-zag pattern caused by growth bending at the nodes. The seedhead is easily identifiable, resulting in a wide spreading panicle when mature.
For those in Grundy County and surrounding areas, Illinois Extension and the Kendall-Grundy Farm Bureau are partnering to host University of Illinois plant pathologist Dr. Boris Camiletti on Wednesday, August 28th at 1:30 pm at the Kendall-Grundy Farm Bureau building. Dr. Camiletti will lead a discussion on his research projects and share experiences in his first Illinois growing season. Producers, landowners and agronomists are encouraged to bring plant samples the afternoon of the meeting for discussion or identification purposes. Anyone is welcome to attend, the Kendall-Grundy Farm Bureau building is located at 4000 N. Division street in Morris, Illinois.