Effect of in-canopy foliar fungicide applications in corn on spray coverage

Foliar fungicides are available to suppress Diplodia ear rot (DER), caused by Stenocarpella maydis (Berk.) Sutton and Stenocarpella macrospora (Earle) Sutton) in corn (Zea mays L.), but previous research has indicated these fungicides have limited efficacy against the disease using traditional over-canopy application methods. In an effort to improve coverage within the canopy and potentially improve disease control of DER, experiments were conducted in 2020, 2021, and 2022 to examine the effect of ground-driven, in-canopy fungicide nozzle technology on DER severity and spray coverage on the ear leaf and ear of corn plants. Application methods included over-canopy nozzles, over-canopy + drop nozzles, and over-canopy + 360 Undercover nozzles. Within each application method, treatments consisted of a non-inoculated control, or were inoculated with a conidial suspension of S. maydis. The fungicides benzovindiflupyr + azoxystrobin + propiconazole and pydiflumetofen + azoxystrobin + propiconazole were applied within each application method to measure efficacy against DER. In all years, neither fungicide product nor application method reduced DER severity. No fungicide applications increased yield compared to the non-treated control. The addition of drop nozzles or 360 Undercover nozzles to traditional over-canopy nozzles increased spray coverage on the ear (P < 0.0001) compared to over-canopy nozzles alone.