As of Wednesday (8/12) afternoon, the crop in southern McLean County was still standing and, for the most part, looking healthy following the storm system that moved through a couple hours prior to my survey. As I write this the following day, another strong storm system is moving through the region bringing more heavy rain and high winds, so I am uncertain if that has changed the crop conditions in that part of the county.

Soybeans in southern McLean County are primarily in the beginning seed (R5) growth stage, ranging from full pod (R4) to early full seed (R6), and are still relatively free of disease or insect issues. Corn is reaching late dough (R4) and early dent growth stages (R5). Remobilization of nutrients from lower leaves is starting to pick up pace in some corn fields that are a bit closer to maturity or in areas of fields affected by early-season wet conditions. Diseases, such as gray leaf spot and Physoderma brown spot, were present in a few of the fields visited, but still no sign of tar spot or southern rust in the fields surveyed. Both have been identified in neighboring counties, Livingston for tar spot and Champaign for southern rust. So, it is possible that those diseases are in the McLean County, but still at low levels. Counties where tar spot and southern rust have been identified can be seen on Crop Lookout from the Crop Protection Network. Links to that resource as well as more information about managing these diseases can be found in the following articles from Extension Field Crop Pathologist, Dr. Boris Camiletti.

Tar spot – https://farmdocdaily.illinois.edu/2025/07/tar-spot-on-the-move-tracking-and-managing-an-established-corn-threat-in-illinois.html

Southern rust – https://farmdocdaily.illinois.edu/2025/07/tar-spot-on-the-move-tracking-and-managing-an-established-corn-threat-in-illinois.html

To report either of these diseases in your area, email photos directly to Dr. Camiletti at bxc@illinois.edu and/or submit samples to the Plant Clinic (https://extension.illinois.edu/plant-clinic).