Precipitation this past week brought substantial rainfall totals to some fields in Northeast Illinois. Isolated corn fields are showing significant disease pressure but are also nearing maturity. In the R5 stage, the corn kernel contains both “soft” and “hard” starch. The transition, or hardening, of the soft starch into hard starch begins at the top of the kernel and progresses to the tip. This progress is visible as the kernel’s “milk line.” Corn is typically about 55 percent moisture at the beginning of R5 and 30 to 35 percent at its conclusion. Corn plants generally complete the R5 stage in about 30 days, during which they accumulate dry matter content.

The soybean crop is nearing the R6 stage. At R6, or full seed, plants have a green seed that fills the pod at one of the top four nodes on the main stem. Once soybeans reach R6, new leaf growth ceases, and lower leaves begin to yellow and drop. We are encouraging growers, especially those with a history of the disease, to monitor their fields for white mold.

For those attending the Farm Progress Show next week, visit Illinois Extension at the University of Illinois College of ACES tent on West Progress Avenue.

This week, Dr. Giovani Preza Fontes, assistant professor and agronomy extension specialist at the University of Illinois, visited the Grundy-Kendall County area and met with area producers, where he shared expectations for 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 the R5 stage, and the likelihood of a return on investment from 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 like taking 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.

A week without precipitation, and northeast Illinois returns to abnormally dry on the U.S. Drought Monitor. Disease pressure in corn is starting to build as much of the crop has reached R4 (dough stage). A Corn Fungicide ROI Calculator tool—accessible on the Crop Protection Network website—is designed for both gray leaf spot and tar spot when corn is in the V10 to R3 growth stages. It requires inputs for expected yield, marketing price, and either a low or high disease estimate. Using those inputs, the tool provides a breakeven probability for most commonly used fungicides. Iowa State suggests that, regardless of which fungal diseases are present, a fungicide application after R3 is not likely to provide a return on investment.

This week I traveled to campus for the Illinois FFA Crop Scouting Competition. A windshield survey of the 90-mile trip on backroads from Champaign north to Grundy County suggests, once again, some remarkable corn and soybean crops in this region of the state.

And just like that, conversations on drought have ended (for now) in northeast Illinois. Cumulative precipitation exceeded four inches in some areas last week. While the rain is welcome, earlier-planted corn that pollinated during the dry stretch has experienced kernel abortion. More favorable growing conditions should enhance grain fill and benefit later-planted and longer-maturity corn.

Dr. Boris Camiletti posted a “Red Crown Rot Progressing in Illinois” Bulletin article on July 28. The disease has been confirmed as far north as Livingston and Kankakee Counties. Growers in northeast Illinois are encouraged to watch for SDS‑like foliar symptoms in soybean and to submit samples to the plant clinic for confirmation.

Illinois Extension and the Kendall‑Grundy Farm Bureau are hosting a 2025 Crop Development Update meeting on August 12 at 11250 N. Church Road, Minooka. The meeting begins at 1:30 p.m. Dr. Giovani Preza‑Fontes, University of Illinois Agronomy Extension Specialist, will share expectations for a growing season filled with temperature and precipitation extremes. In addition, Steve Brand, Northern Illinois Extension Specialist, will provide insights into plant diseases observed across northern Illinois. This meeting is open to the public.

Despite nearly an inch of precipitation over the weekend, many grass areas have yet to come out of dormancy in regions that were previously very dry. Tar spot confirmation frequency is increasing in northern Illinois counties and merits attention. Isolated southern rust infection was also detected this week in the area. Dr. Boris Camiletti addressed southern rust identification and management in a July 19 Bulletin article.

In R3 (milk stage) corn that was scouted, corn earworm (CEW) was found. While generally not an issue in dent corn, it can be problematic for sweet corn. The female CEW moth lays individual eggs, preferably on fresh corn silks. After hatching in 2–5 days, the larvae move to the tip of the developing ear to begin feeding. Once inside the ear, there is no effective control for the pest.

For a more upbeat report, I would encourage you to read my coworker Steve Brand’s report. Last week, in the area Steve covers in Northern Illinois, many fields received between 3 and 5 inches of rainfall. In areas including Kendall, Grundy, and Will, the rainfall totals measured in tenths. As many corn fields are at or nearing VT and R1 (tassel and silk stage), an expected result of the moisture stress is kernel abortion. Moisture stress at this time can interfere with pollen shed and silking synchronization. In addition, high temperatures coupled with low humidity can desiccate exposed silks.

Can farmers evaluate the pollination process? After successful pollination and fertilization of the ovules, the silk will detach from the developing kernel. Evaluating pollination success can be done with the ear “shake test.” Carefully unwrap the husk and gently shake the ear; the silks from the fertilized future kernels will readily drop off.

As long as we have kernels and green tissue for photosynthesis, we can remain hopeful for the corn crop. Our soy crop, while visibly shorter this year in the dry fields, can recover more readily if forecast moisture alleviates growing conditions in this area.

More hit-and-miss rainfall last week in NE Illinois as additional corn acres begin to reach VT (tassel). Areas that received rainfall are faring considerably better than those that did not. Corn growing in fields with gravelly knolls and lighter or sandy soils that did not receive recent rains is showing significant stress. Fungicide applications have started in the area. In scouting visits to R1 corn fields, the only disease noted was sporadic Northern corn leaf blight. This disease is recognizable by the cigar- or canoe-shaped lesions formed on leaf tissue. The causal pathogen for this fungal disease overwinters on corn leaf debris. Hybrid resistance is normally adequate for management of the disease, but substantial losses can occur with early infection and susceptible hybrids.

Interesting, but normally not economically important, leaf feeding was also noted in the corn. The corn blotch leaf miner is a small fly that deposits eggs on either the upper or lower corn leaf surface. After hatching, the larva tunnels in the leaf, feeding on the inner leaf tissue as it grows, leaving behind mines or transparent galleries. Eventually, the larva chews its way out of the leaf, drops to the soil, and pupates. I’m finding very limited leaf feeding, despite the presence of Japanese beetles, and no diseases at this point in the growing season in the soybean fields visited.

Almost every growing season, farmers reach a stretch where the crop is “holding on.” That description fits much of northeast Illinois, as additional acres fall into the abnormally dry to moderate drought category on the U.S. Drought Monitor. With high daytime temperatures, corn plants are starting to “wrap” to conserve moisture. We are starting to see tassels appear on the earliest planted corn as it reaches a critical, yield-determining stage. Tar spot is starting its spread across Illinois, and statewide reports can be followed on the Corn ipmPIPE website: https://corn.ipmpipe.org/tar-spot/. This week, we are also in the window for applying white mold fungicides. The Crop Protection Network provides a risk assessment tool, using current weather data to help in fungicide decision-making: https://connect.doit.wisc.edu/cpn-risk-tool/. Limited precipitation has allowed for a quality second cutting harvest. Happy Fourth of July to all!

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.