Comparison of aerial and ground sprayer fungicide application technologies on canopy coverage, disease severity, lodging, and yield of corn

Abstract

Fungicides may be applied to corn using an airplane or a ground sprayer. Questions regarding which technology is better at coverage throughout the corn canopy are common among farmers and agronomists. The objectives of this study were to compare the efficacy of three application technologies in terms of canopy coverage, foliar disease management, lodging and yield response. A fungicide was applied to corn at silking (R1) by airplane, a traditional ground sprayer with an overhead spray boom, or a ground sprayer with 360 Undercover sprayers that hang down into the canopy. Replicated on-farm and small-plot trials were conducted across Iowa in 2017 and 2018 for a total of nine site-years. Fungicide coverage was measured as ppm of pyrenetetrasulfonic acid (PTSA) dye detected on corn leaves, percent coverage of water sensitive spray cards, and percent of total application received. Foliar disease data were collected in three zones of the canopy: the upper canopy (UC), the ear leaf (EL), and the lower canopy (LC). Coverage and disease severity were not correlated with yield. In the 2017 on-farm trials, all three application methods delivered similar fungicide coverage on the EL and LC. In 2018, traditional and undercover methods provided greater coverage when compared to aerial application, however, fungicide distribution within the canopy was similar among the application methods. Overall trends indicated the traditional spray method delivered the best coverage to the UC. The aerial spray method delivered the least coverage to the EL and LC for three site-years. The undercover spray method resulted in greater coverage to the LC. Foliar fungicides applied by all three application methods significantly reduced foliar disease severity, and fungicide application methods did not differ from each other, and reduced disease severity to similar levels. Lodging was reduced approximately 50–75% by all application methods. For 8 of 9 site years, fungicide application did not affect yield significantly (P > 0.05), although numerically less yield was consistently recorded in the non-sprayed controls. Our findings indicate these three application technologies were similarly effective in reducing plant disease levels and lodging. But the reduction in disease due to fungicide application did not affect corn yield.