A Report from the 2026 Meadowlark Extension District Corn Disease Tour
*DISCLAIMER: information is current as of 5:30 p.m. on 07/01/26 and subject to change (it might change BEFORE I hit publish!). Please check the maps below to monitor disease progression and utilize all scouting methods (field evaluations, drone/satellite imagery, etc…) to ground truth these findings.
9 fields across 3 counties were visited yesterday (June 30th) as part of a corn disease tour with K-State Extension Row Crops Pathologist Dr. Rodrigo Onofre. Here’s what we found (click here for a video summary and select 2026 Corn Disease Tour):
- Gray Leaf Spot (GLS) was the primary fungal pathogen noted. While most pressure was relatively slight, 1 of the 9 fields had pressure that would likely respond to a fungicide application. **
- Southern Rust was not present and has only been from middle TX south.
- No new counties were confirmed for *Tar Spot. Only one small lesion was found from a field in a county where it had previously been confirmed. NOTE: current heat may slow Tar Spot growth/spread, but if temperatures begin to trend lower, the disease could pick up again.
- Northern Corn Leaf Blight and Bacterial Leaf Streak (BLS) were also noted at low levels. **NOTE: additional scouting today (07/01) revealed varying degrees of BLS in multiple fields. It’s similarity to GLS requires careful observation to tell the difference. GLS can be treated with a fungicide. BLS cannot.
- Physoderma Brown Spot was also present in multiple fields.
Dr. Onofre offered these tips:
- Optimum application window is VT/R1 (tasseling) to R3 (milk). R4 and beyond applications hold much less potential for ROI. If disease pressure is low in your fields, consider delayed applications – the protection time frame for a fungicide is 2-3 weeks.
- Choose fungicides carefully. If in doubt, check out the Crop Protection Network Fungicide Efficacy resource.
- Generics can provide good efficacy. Check out Dr. Onofre’s work with numerous products in the 2025 Kansas Corn Disease Management book.
- Beware of untested biologicals. Try them in a small area if you can. Results have been somewhat inconsistent.
In addition to these tips, check out a recent KSU Agronomy eUpdate article from Dr. Onofre here.