Last weekend’s 3+ inches of rain gave a much-needed boost for crops across Logan County. While some areas may still exhibit signs of heat stress, most fields appear strong and healthy. Corn at the University Research Plot in Hartsburg and across much of the county is in at least the R3 “milk” stage, with some in the R4 “dough” stage. The same can be said of soybeans, with nearly all fields having pods at various stages of development. Cooler temperatures and more rain in the next week will undoubtedly be welcome.

The area is still behind on moisture, but rains over the weekend have certainly helped reduce some stress during this critical period for both corn and soybeans. Early-planted soybeans are setting pods well so far and can be staged at mid- to late R3 through R4 at this time. Later-planted beans range from mid- to late full bloom (R2) to mid-R3. Most of the corn has pushed into pollination or has completed pollination. Most fields I’ve been in are staging early to mid-blister (R2). Later-planted fields are just starting to tassel and show good silks.

It’s another hot week upon us as a heat dome settles over the Midwest. July so far has brought 3.5 to 5 inches of rain, depending on the area, excluding Will County, which remains in a somewhat severe drought. Northwest Illinois is on pace with historical averages and enjoying a great growing season. South of Chicago and some suburban counties are drier than normal and continue to be in either a D1 or D2 drought. Corn planted on April 25 is likely around 1,500–1,600 growing degree units for the season.

Corn is mostly tasseled across the region, ranging from R1 to R2 (blister stage) and looking very healthy. With recent rains, disease has finally arrived across northern Illinois. I confirmed tar spot in DeKalb, Kane, McHenry, and Lake counties this week, with strong suspicions it is also present in DuPage and nearby counties. All plants I scouted had one or two lesions on the leaf below the ear leaf. At this point in the season, most fungicides have already been applied and should protect the crop through harvest. Scouting will help determine if additional sprays are needed, though anything after R3 is generally not recommended. Gray leaf spot has also been working its way up corn plants.

Soybeans are progressing well. Disease pressure is low, and they are moving into R4, with 3/4-inch pods. While we’re still seeing some stunting in northern Illinois from early drought and delayed emergence, overall soybean health looks good. Not much else to report, as pods are setting and filling.

Corn and soybeans have benefited from July rainfall. Both continue to progress quickly, with growing degree days maxing out. Various leaf diseases are present in corn, including gray leaf spot and northern corn leaf blight. Be on the lookout for Tar spot and southern rust—these can be especially devastating if left untreated. Continue to be diligent in your scouting and spray if needed. Leaf flaring is occurring in some fields, which is not normal for this time of year.

The only issue I’ve seen in soybeans is the pesky Japanese beetle. On average, I’ve seen 5% leaf damage on the low end and 10% on the high end. Begin treatment at 10% if soybeans are in the beginning pod to beginning seed stages.

With frequent rains over the past couple of weeks, topsoil moisture remains adequate, and crop health is looking good across Coles County. Full-season soybean fields ranged from R3 (beginning pod) to R5 (beginning seed). I saw minimal disease in the soybean fields I surveyed. Minor Japanese beetle feeding was common in fields visited, although it was generally contained to the uppermost leaves and resulted in less than 5% defoliation overall. The couple of double-crop soybean fields I found were in the V3–V4 range, with growth just starting to poke through the wheat stubble. Corn fields were generally around the R2 (blister) stage, with some stragglers still in R1 (silk) and a few early-planted fields reaching R3 (milk). I saw minimal foliar disease in the corn fields I walked into, although some common diseases—such as northern corn leaf blight, Physoderma brown spot, and common rust—are starting to show up in the lower canopy.

April-planted beans are at R3–R4; early May-planted beans are at late R2. I haven’t seen much disease in soybeans other than the normal leaf blight. Japanese beetles and grasshoppers are in the bean fields and seem to show some preference for certain varieties over others. I think most of the fungicide applications will be completed in the next 10 days. Tar spot in corn continues to be top of mind; we’ve been monitoring the pressure, and while it hasn’t exploded yet, it has progressed in most fields over the past 10 days. Most of the corn fungicide will go on in the next 10–14 days, if not already applied.

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.

We received some much-needed (if sporadic) rainfall in the last week that has crops looking much better than in previous weeks. Areas of Bureau County reported over 5 inches on Friday night, though that storm system petered out by the time it reached LaSalle County. LaSalle County did receive about 2 inches of rainfall on Wednesday night. Thankfully, temperatures have also cooled off a little bit for the time being, and there is more rain in the forecast for this weekend and early next week.

Overall, crops are looking healthy. Wheat in LaSalle County was harvested the first week of July. Most corn is now reaching VT/R1. Most soy is entering reproductive stages, with many fields at R3. I have not seen any serious disease or pest concerns in the fields I have scouted, but tar spot has now been reported in LaSalle, Bureau, and Marshall counties, so growers should continue to scout fields and be on the lookout for this disease. Corn is reaching the growth stages where it could benefit from a fungicide application, and I have seen both ground and aerial sprayers at work in the past week.

I have received a few reports of corn leaf aphid. This insect should be scouted prior to tasseling, during late vegetative stages; if you have colonies of aphids formed on around 50% of plants at this time, you should consider an insecticide. Beneficial insects and fungal pathogens usually do a number on this pest, and it takes extremely large populations to impact yield.

Last week brought sporadic pop-up showers that benefited some fields needing a shot of rain to support growth and development in the reproductive stage. A few corn fields are still in the late V-stages, while nearly all have tasseled and ears are beginning to show. The same can be said of soybeans, with nearly all fields across the county at least in the R2 stage.