A panel of Indiana Certified Crop Advisers discussed on May 5 whether one or two fungicide applications are needed for corn this season, responding to questions about disease pressure and optimal timing.
The topic is important as farmers consider how best to manage crop diseases like southern rust while balancing costs. Experts say that the number and timing of fungicide applications can significantly impact yield and profitability.
Gene Flaningam said, “Research shows that corn fungicide application should be done at VT to R1. Do not judge your fungicide application based upon the prior years’ disease progression. Scout those fields after the initial fungicide application, at approximately the R3 growth stage. Make a management decision on whether to apply a second fungicide based upon the hybrid’s disease tolerance, severity of disease infestation and crop growth stage. Lastly, review the weather forecast. The air temperature and humidity are key factors that can enhance disease progression.” Carl Joern added, “One well-timed pass can be as effective as two suboptimally timed passes. Fortunately for you, southern rust does not overwinter in our area. Just because you had it bad last year doesn’t mean much as it relates to 2026. If you’re making one fungicide pass, VT/R1 is the sweet spot. University data and on‑farm trials confirm this is the most reliable ROI timing.” Joern also noted that high-risk areas may justify a second pass if disease is present and spreading but cautioned that most years require only one well-timed application.
Greg Kneubuhler said, “A single fungicide pass in corn is typically the most profitable approach. Timing is far more important than the number of applications… Only consider a second pass if multiple risk factors are present, such as early disease development, susceptible hybrids, continuous corn or favorable weather for disease.” Dan Quinn advised farmers: “Foliar fungicide applications at R1 to R2 tend to provide the most consistent and reliable disease control and yield response when disease pressure is present… Multiple fungicide applications are typically only justified in fields with severe, early-developing disease pressure… Without early and escalating disease pressure, a second pass rarely provides a consistent economic return.” Quinn emphasized scouting regularly since southern rust’s arrival varies each season.
Farm Progress supports agricultural communities by offering resources like market updates and educational programs; it functions within Informa PLC’s Informa Markets Division; distributes content through 18 regional brands; delivers news analysis tools; organizes events such as Farm Progress Show; extends its reach via publications digital platforms according to Farm Progress.
Looking ahead, advisers recommend close monitoring of local conditions throughout the growing season before deciding on additional treatments.
