Sometimes the best way to help growers plan for next season’s corn inputs is to look backward.
Stalk condition, ear rot symptoms and signs of foliar disease in crop residue can reveal which fields may carry greater disease risk into the coming season and help guide more targeted preseason recommendations.
Document what the field is telling you
Pre- and post-harvest observations can help growers understand what happened in each field and identify potential risks for the coming season. Walk them through three quick assessments to establish a disease-history baseline.
- Stalk integrity: Use pinch and push tests to identify weak stalks and possible stalk rot. Pinch the lower internodes to check for soft or hollow tissue, then push plants approximately 30 degrees from vertical to see whether they recover or break. Record areas with a high percentage of compromised stalks, since they may indicate greater disease pressure or crop stress.¹
- Ear health: Inspect ears from several locations across the field for mold symptoms, discoloration or damaged kernels. Note the type and severity of symptoms, along with where they occur, because ear rot can vary considerably within a field and may affect harvest, storage and grain-quality decisions.²
- Foliar disease history: Record diseases such as tar spot, gray leaf spot and northern corn leaf blight, including their severity and distribution. Note which hybrids were affected, where symptoms were most concentrated and whether disease reached the upper canopy, since those details can help identify fields and hybrids with greater future risk.
Convert corn disease history into a field-specific risk profile
No single factor defines corn disease risk. Instead, help growers consider crop rotation, residue levels, tillage practices, hybrid susceptibility, previous disease severity and weather patterns together.
Fields planted in continuous corn may carry a greater risk from diseases such as gray leaf spot, tar spot, and northern corn leaf blight because infected residue can allow pathogens to survive between seasons.³ Reduced-tillage systems may preserve more of that residue on the ground, increasing the importance of suggesting hybrid seed with appropriate resistance and recommending routine scouting. Fields with a history of tar spot also deserve closer attention, particularly when susceptible hybrids and cool, humid conditions coincide.
The purpose of this conversation isn’t to assume that disease will return at the same level. It’s to identify where risk is the biggest concern so growers can compare hybrids, prioritize scouting and make more informed fungicide decisions before the season begins.
Use the risk profile to guide preseason decisions
Once you understand disease pressure and field management, organize recommendations around three decisions: hybrid selection, cultural practices and fungicide planning.
Start with hybrid selection by matching disease-resistance ratings to the field’s history and reviewing university trial data when available.
Next, consider whether crop rotation, residue management or tillage could reduce risk in fields with a history of residue-borne diseases. Corn-on-corn and reduced-tillage fields may also require more deliberate hybrid selection and scouting.
Finally, identify fields where disease history, hybrid susceptibility and favorable weather may justify applying a fungicide for gray leaf spot or other fungal diseases. For tar spot in corn, the decision window commonly extends from VT to R3, while VT applications may be most effective against gray leaf spot under high pressure.⁴ Base timing on disease development and field risk, then use those same factors to evaluate potential ROI rather than relying on a calendar-based application.
Make corn disease planning part of the sales conversation
Review each grower’s field records before finalizing preseason recommendations. By helping growers navigate disease risk and identify appropriate solutions, you can build trust as a knowledgeable adviser.
When recommendations begin with field history, you can help growers concentrate management investments where disease risk and potential return are greatest.
Experts are available to help you make your corn disease management decisions. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.
________________________________________________
Endnotes
- Kness, Andrew. “Scouting for Ear and Stalk Rots in Corn.” University of Maryland Extension, 22 Oct. 2024,https://extension.umd.edu/resource/scouting-ear-and-stalk-rots-corn/.
- Kness, Andrew. “Scouting for Ear and Stalk Rots in Corn.” University of Maryland Extension, updated 22 Oct. 2024, extension.umd.edu/resource/scouting-ear-and-stalk-rots-corn/.
- Robertson, Alison, and Gary Munkvold. “Disease Management in Corn-Following-Corn Fields.” Integrated Crop Management, Iowa State University Extension and Outreach, 12 Feb. 2007, crops.extension.iastate.edu/encyclopedia/disease-management-corn-following-corn-fields.
- Life, Rosemary. “Tar Spot of Corn: Fungicide Management.” Virginia Cooperative Extension, 18 May 2026,www.pubs.ext.vt.edu/content/pubs_ext_vt_edu/en/SPES/spes-812.html.
