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.

Rain is in the forecast which would greatly benefit the soy crop in drier areas of Northeast Illinois, that crop is still at R5 or beginning seed. As we reach mid R5 we can expect the remobilization of nutrients from leaves and stems to start. While few reports of soy disease have been noted to date, a report of White Mold in Kane County was shared this week. Most corn fields visited are now at some stage of R5 or dent stage. In lighter soils lacking rain, significant firing is evident. As our crops near maturity many farmers have turned their attention to readying combines and other harvest equipment. While important, we can also find value in late season scouting visits. This week has been a very interesting in corn leaf diseases, Tar Spot continues to infect and spread within and across fields. This is the time to evaluate fungicide application efficacy or hybrids inherent or bred tolerance to Tar Spot and other diseases. In addition to Tar Spot, symptoms of Northern Corn Leaf Blight, Gray Leaf Spot and Southern Rust can be found in area corn fields. Visiting fields with disappointing weed control can also provide insight into management decisions in future years. Included is an image of Waterhemp treated with a tank mix of Enlist and Liberty that killed the apical meristem but not the plant. In visiting Dr. Aaron Hager, Weed Specialist at the University of Illinois, he shared the current message for Waterhemp control in soy. I had to chuckle (and could relate) at recommendation 7.
1) Use glufosinate with Enlist One instead of glyphosate. If we miss grass with the tankmix, we can always come back and clean it up with glyphosate. We do NOT want to miss the waterhemp with the first application.
2) Keep the water volume close to 20 gpa whenever possible.
3) Be sure to use the correct spray tips; these drift reduction nozzles are terrible for contact herbicides, such as glufosinate.
4) Spray small waterhemp. If the field average size is 4 inches, the reality is a field with plants ranging from 8 inches to ½ inch.
5) Keep the AMS at the label recommended rate. This is NOT the place to cut costs.
6) Glufosinate likes bright sunshine, high air temperatures, and high humidity. Applications made when one or more of these are missing often are somewhat compromised.
7) Spray glufosinate like you once sprayed Basagran (that one resonates only with those with at least a touch of gray hair).

This week precipitation has been mixed in northeast Illinois, areas north of the Rte. 80 corridor have received multiple rainfall events while areas south have received limited to no precipitation. Soy continues to progress, reaching R5, beginning seed stage. Depending upon variety maturity and planting date, most corn fields visited were R3-R4 to R4-R5. An unwelcome discovery this week was significant Tar spot symptoms in several corn fields. The decision on using a fungicide treatment is difficult in later maturity stages, especially when we are near R5, the dent stage. A reminder that grain fill in the dent stage often extends to 30 days or more. However, with declining commodity prices farmers need to consider their ROI (return on investment) when considering a or additional fungicide applications. A tool available to aid in the decision making is the Corn Fungicide ROI Calculator from the Crop Protection Network. The purpose of the Corn Fungicide ROI Calculator is to share results from university uniform corn fungicide trials conducted in the United States and Canada and allow farmers and others in the agricultural industry to calculate the potential return on investment (ROI) for corn fungicide application across a variety of user-defined factors, which is based on research data included in this calculator. The two variables needed are expected corn yield and marketing price. The calculator can be accessed at https://cropprotectionnetwork.org/fungicide-roi-calculator

As July ends warmer temperatures and humidity returned to NE Illinois. While some appreciate seeing a sunrise mist with morning coffee, I think of extended leaf wetness on crops and that it often favors fungal leaf diseases. Despite these occurrences, I continue to see very limited leaf disease symptoms in corn or soy. From a maturity standpoint in fields visited, corn is transitioning from R3 (milk) to R4 (dough) stage. The starch within the kernel is converting from a liquid to a pasty consistency. R4 is often the shortest reproductive stage dependent on environmental conditions. Soy has reached R4 or the full pod stage. At this stage a ¾ inch (2 cm) pod can be found on one of the 4 uppermost nodes on the main stem. R4 through R6 (full seed) is a critical time for the soybean plants exposed to environmental stresses. Issues at this time can cause more significant yield decreases than other growth stages.
Recently Dr. Doris Lagos (USDA-ARS) at the University of Illinois reported finding corn aphids in the suction trap network https://suctiontrapnetwork.org/data/ and in fields. Several have corroborated finding corn aphids and suggested treating specifically for the pest. In my scouting visits I am finding corn aphid populations where I often find them, on plants at or near field edges, and at very low densities (random mostly singular plants).

Another week of varied precipitation in northeast Illinois, but mostly favorable growing conditions. Corn has reached R3 (milk stage). At this stage the moisture of the kernel is about 80%. Leaf disease incidence continues to be low in corn and soy fields visited. Most soy is R3 to R4, beginning to full pod. In addition to the crops entering their reproductive stages, so too are some weeds, including waterhemp. This weed is dioecious, both male and female plants having flowering structures. Once mature, the plants can be easily sexed by the presence or lack of shiny black seeds.
This week I attended the Monmouth Research Center Agronomy Day and was able to gain insight explaining why many were seeing waterhemp uncontrolled by post herbicide applications. The surviving plants appeared weeks after the post herbicide application as bushier, more robust plants. University of Illinois ‘s Caleb Wepprecht discussed “HPPD Resistant Waterhemp- A Growing Concern” and shared his take on weed control challenges from this year. A few factors in waterhemp escapes were inadequate spray volume on larger plants, leading to inadequate coverage of the growing points, even with systemic herbicides, as well as low use rates/dosage of herbicide in the weed itself, along with the concept of metabolic herbicide resistance, leading to the waterhemp’s survival and altered plant structure. As farmers see waterhemp escapes in fields, Caleb encouraged attendees to take whatever steps possible to prevent the prolific seed-producing weed from maturing and causing future concerns

An active week on the weather front in Northeast Illinois. Several storms packing high winds roared through the area. Despite this, to date, I have heard few reports of down corn. Regional corn fields are at varied maturities because of planting dates. The earliest planted has reached R2 (Blister), the developing kernels appear as clear fluid containing whitish blisters on the cob, silks are brown and drying rapidly. Most soy is also at R2 (full bloom) and closing canopies in 30″ rows. Fungicide applications are underway by plane, helicopter and drone (and likely ground rigs when field conditions permit). I noted isolated incidence of Gray Leaf Spot and Tar Spot this week, I plan on revisiting those corn fields within the week to reassess. On some corn plants lower leaves exhibit the inverted V symptoms of nitrogen deficiency. Leaf senescence occurs naturally and is identified by corn leaves losing greenness due to a reduction in chlorophyll. Not all nutrients are lost, some assimilates are “remobilized” and transferred to the ear and kernels so that grain fill can be sustained and completed. While a natural process, lower leaf senescence and its counterpart, top dieback, can also be initiated by crop stresses and bears watching in future field visits.

The remnants of Hurricane Beryl passed through northeastern Illinois depositing widespread and varying precipitation. Area wheat growers who have yet to harvest are facing an extended combining schedule and likely lower test weights as the grain rewets and dries. Many corn fields are currently pollinating, always an uncomfortable time to scout. Even so, it is still a critical time to do so, determining leaf disease pressure and fungicide application decisions. Current commodity prices suggest an eight to ten bushel preservation of yield is necessary to justify the cost of most aerial applications. I have yet to see Tar spot, but an agronomist further southeast shared that symptoms have been found. The University of Illinois Plant Clinic is offering free Tar Spot screening again this year. The downloadable screening form can be found at https://extension.illinois.edu/sites/default/files/2024-06/2024_free_corn_tar_spot_form_0.pdf . Waterhemp is starting to push through soy canopies and many conversations in July have centered on resprays and herbicide dissatisfaction. Make note and evaluate your level of control in fields as you plan for 2025. I always enjoy seeing brace root emergence in a corn field. I note hybrid differences and have heard a plant breeder suggest that brace roots are a photosynthetic drain on a corn plant yield potential. Whether it helps or hinders final yield, I feel better when seeing corn plants with the additional anchoring support of brace roots that make it to the soil. In my mind, it’s going to help that plant stand through harvest.