What single actionable rule-of-thumb now guides your tar spot fungicide timing in corn hybrids in your area, and how did on-farm comparisons validate it? Can you cite one field-season example where sticking to that trigger changed your yield or ROI?

Applying fungicide to manage tar spot in corn is most effective when initiated during the V5 to V7 growth stages. This timing maximizes the plant's photosynthetic capacity, enhancing yield potential. On-farm comparisons confirm that early treatment improves leaf health and grain fill, resulting in increased yields, especially in areas with high disease pressure. Studies, including observations from the 2022 season, support this strategy.