The past two weeks have seen late-season leaf diseases appear in area fields: tar spot, common rust, southern rust, gray leaf spot, and others. A few farmers have taken out end rows in corn fields. In moderate drought areas, corn fields have fired up to the ear in the drier parts of the fields. Corn fields are in the dent stage (R5), and a few fields are in the mature stage (R6).

Soybean fields are turning yellow, reaching the R7 (beginning maturity) stage, with early-maturity soybean fields at or nearly at the R8 (full maturity) stage.

To put it simply, it’s a race to the finish in corn. Tar spot and southern rust are really taking over the plant as we start September. The cool temps, coupled with fungicide residuals wearing off, are the perfect recipe for disease. In beans, you’re just starting to see some early maturities turn. Over the last couple of weeks, I have started to see sudden death and white mold, with sudden death seeming more prevalent. The rain in mid-August really made me more optimistic about the bean crop, but if we could catch another rain in the next 10 days, that would be ideal.

It feels very fall-like with low humidity and temperatures in the low 80s. The crop is proceeding well, and some corn and soybean harvest will begin next week, mainly March corn and late group 2 soybeans.

Conditions remain dry. We haven’t had significant rainfall since mid-July, and while some subsoil moisture is present, the area’s high clay content limits plant availability. After several weeks of heat, corn is showing stress, with leaves firing in areas of thin soil or earlier-season ponding. Corn is beginning to dent.

Most first-crop soybeans are in the R4 to R5 stages, depending on planting date. Later-planted and double-crop beans are still in R2 to R3 and could benefit from late-season rainfall, similar to the inland hurricanes from the Gulf that have boosted yields in recent years.

Rain showers earlier this week brought much-needed moisture to the area, giving some fields a boost. Most of the corn in Logan County has entered the R5, or dent, stage, with some fields still in R4, or dough. Soybeans are showing similar progress, with most fields in the R5 stage. The growing season is nearing its end, and some plants are beginning to show signs of full maturity.

After a wet couple of weeks in Northern Illinois, precipitation levels are nearly back to normal for the season. Most areas received 1 to 4 inches of rain over the past weekend, depending on storm tracks, which has primed plants to finish strong through ear and pod fill. Disease has become more prevalent as rainfall increased and temperatures dropped from the 90s.

Corn across the region is entering the dent, or R5, stage, with kernel development varying by planting date. Tar spot is usually the primary concern, but early southern winds this season brought in southern rust. While southern rust generally does not cause major yield loss, it may slightly reduce yields in fields that were not treated with fungicide. Because the disease does not overwinter in northern climates, it is not expected to be an issue next season. Tar spot is moving into upper canopies, but spraying this late is not recommended due to limited return on investment. Another issue observed in multiple fields is tip-back on corn ears, likely caused by poor pollination during extreme heat and drought earlier in the season.

Soybeans continue to look strong. With their height later into the season, some fields experienced slight lodging after severe storms over the weekend. Disease pressure remains low overall. White mold was found for the first time this season in some lodged beans, but incidence is expected to remain low due to drought and high temperatures during flowering. Overall, soybean yield potential looks very good.

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.

Soybeans in many fields are reaching the R6, or full seed, stage, and late-season insect and disease pests are beginning to appear. A few fields are nearing R7, or beginning maturity.

Champaign County received much-needed rain this past week, totaling about 1 to 1.5 inches. During a survey of the southern half of the county on Aug. 20, surface soils in most fields were still slightly wet from the previous morning’s storm, with the southwest corner a bit drier than the rest of the area. Corn fields surveyed were generally in the late R4, or dough, to R5, or dent, growth stages. The severity of tip dieback ranged from minimal to more than 2 inches across the area.

Full-season soybeans were generally in the R6, or full seed, stage, with a few fields beginning to drop leaves and enter R7, or beginning maturity, at least in parts of the field. I also came across a couple of double-crop soybean fields, both just entering the R3, or beginning pod, stage. One of these fields featured a placard from the Illinois STAR Program, which connects farmers using conservation practices with end-users willing to pay premiums that support those practices.

Southern Illinois experienced planting delays this spring due to excessive rainfall, which pushed field activities into late May and early June. Despite these challenges, soybeans are currently at the R2 (full bloom) growth stage, and the corn that was planted has also reached reproductive stages. One field I scouted showed significant defoliation caused by insect pressure from bean leaf beetle, Dectes stem borer, and striped blister beetle, all of which can continue to impact soybean growth and development if not properly managed. At the R2 stage, the defoliation threshold for bean leaf beetle is 15–20%, and for blister beetle, it is 15%. At these levels, an insecticide application is warranted to prevent economic yield loss.