Depending on location, we have received between 1.5 and 4 inches of rain in the last week. It had previously been very dry in some areas, while others were lucky enough to get some pop-up showers. We now have the conditions for diseases to start showing up in corn or soybeans, but this will also depend on their disease susceptibility or disease scores. A few Northern corn leaf blight lesions were present in corn, but I was more concerned with the spread of gray leaf spot from the lower leaves. Japanese beetle infestations have ramped up, especially in later-planted soybeans. If farmers have decided to make fungicide/insecticide applications, they will start on corn this week as it has reached the VT growth stage. Early-planted soybeans have canopied and will soon reach the R3 growth stage. If warranted, they will also receive fungicide/insecticide applications at R3.

In Franklin County this week, I found a couple of soybean fields in full flowering (R2), despite being shin-knee high. Beans in this area vaulted straight into flowering at only V5–V6, since days have started shortening after the solstice. Most double-crop beans are in the ground and at VE–VC.

On the corn side, I have seen one field tasseling — it must have been an atypical field that got planted in April. Most corn fields are still vegetative (V9–V10), with no sign of tassels yet.

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.

Currently, the corn and soybean crops are looking good. Some corn in the drier areas has fired on the lower leaves.

Soybeans vary from V5 to R3 (beginning pod), and corn varies from V10 to R2 (blister), with most of the corn crop in the R1 stage. Weed control is generally looking good; however, the amaranths are beginning to poke above the soybean canopy in some soybean fields.

Rainfall over the past 14 days has been over 150% of normal in southern Macon and Piatt counties, and less than 25% of normal through the balance of the three-county area.

Now is the time to begin monitoring corn rootworm beetles — both to evaluate the performance of traits/insecticides used this year and to gauge the need for control next year. We will again be distributing yellow sticky traps to anyone interested in participating in our regional corn rootworm adult monitoring network in 2025 (for more information about the network and to see reports from previous years, visit www.rootwormipm.org).

If you are interested in participating and would like me to send you traps and/or the sampling protocol, please send me an email (nseiter@illinois.edu) with the following information:

• Your name and shipping address
• The number of corn and soybean fields you plan to monitor

The growing season is entering a key phase, during which many fields and plants are transitioning into the reproductive stage of growth. Nearly all of the corn fields in the area have entered the R1 phase, with some likely further along. There are still some fields in the later V-stages, but they won’t be behind the rest for too long. Much the same story can be said of soybeans, with some more mature fields in the R1–R2 phase, while others are in the later V-stages. Rainfall has also been variable across the area over the last week. Some parts of the county received around an inch of rain, while others received a half-inch or less.