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57

Nozzle selection and effective fungicide placement at two application gallonages

Presenter: M. A. Draper

All authors and affiliations: M. A. DRAPER (1), L. J. Giesler (2), B. E. Ruden (1), and T. J. Weissling (2). (1) South Dakota State University, Brookings, SD; and (2) University of Nebraska, Lincoln, Lincoln, NE

Two replicated sprayer trials were established to investigate spray parameters leading to effective fungicide placement in a soybean crop canopy. Studies were performed by the Extension Plant Pathology programs at South Dakota State University and the University of Nebraska, Lincoln. The trials were designed to limit the variables involved in each study. Two application gallonages were targeted, 10 gpa (study one) and 20 gpa (study two). Various nozzles and nozzle configurations were selected that maintain droplet diameters in the medium droplet size category. Each study included four replications and was repeated twice at approximately the V5 and R5 growth stages (approximating 75 and 100% canopy closure). All plots were sprayed with labeled rates of Quadris fungicide and crop oil supplemented with a spray foam marker dye. Droplet collection cards were placed at mid-canopy. In study one, single flat fan or air induction nozzles of various orifice sizes were used at 50 and 75 psi. Application speed was varied to maintain a 10-gpa application rate. For study two, single orifice, twin orifice, and twin nozzle configurations were tested at 50 or 80 psi. Speed was again varied to maintain the desired application rate of 20 gpa. Differences in volume median diameter (VMD) and number of droplets per card were relatively consistent for all trials based on nozzle selection. Effects of canopy density, nozzle selection, and nozzle orientation on mean percent coverage, mean droplets per target card, and mean VMD are discussed.

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