Effect of Fungicide Application Method on Deposition, Disease Severity, and Yield in Short- and Tall-Stature Corn

Fungicide application method and crop canopy structure can influence spray deposition, disease control, and yield in corn (Zea mays L.), yet their interactions remain poorly understood, particularly in short-stature hybrids. Field experiments were conducted in Iowa and Kentucky during 2023 and 2024 to evaluate the effects of hybrid architecture (short- vs. tall-stature) and fungicide application method (aerial, ground, unmanned aerial vehicle [UAV], and 360 Undercover) on spray deposition, foliar disease severity, and grain yield. Fungicide deposition was quantified using a fluorescent tracer dye measured across canopy positions and distances from the spray swath center. Deposition differed among application methods, canopy positions, and row locations, with ground and UAV applications generally providing greater deposition than aerial applications. Deposition was greatest in the upper canopy and declined toward lower canopy positions, whereas 360 Undercover improved lower-canopy deposition. Despite these differences, fungicide applications reduced foliar disease severity relative to the non-treated control across environments, with minor differences among application methods. Tar spot (Phyllachora maydis) and southern rust (Puccinia polysora) were observed in Iowa, while gray leaf spot (Cercospora zeae-maydis, C. zeina) occurred in Kentucky. Grain yield increased with fungicide application, but differences among application methods were small and inconsistent. Overall, results indicate that multiple application systems can provide effective disease control and yield protection when fungicides are applied at the appropriate growth stage, and that adequate deposition, rather than maximum deposition, is sufficient for managing major foliar diseases in corn.