The effect of nozzle type on clodinafop-propargyl potency against winter wild oat

In rational herbicide application technique, a critical management decision to minimize exo- and/or endo-drift is the optimal nozzle selection to spray at wind speed authorized (<1.5 m s−1) and unauthorized (>1.5 m s−1). Two studies were conducted simultaneously to select the optimal nozzles for two windy conditions. In bioassay study, six doses of clodinafop-propargyl (0, 8, 16, 32, 48, and 64 g a. i. ha−1) were sprayed with 10 types of yellow color-coded polymer spray nozzle having a 110° spray angle against winter wild oat at 0.5 and 7.5 m s−1 wind speeds. In drift and deposition study, only the recommended dose of clodinafop-propargyl (64 g a. i. ha−1) was sprayed in the same manner above on the water sensitive papers which were installed in different positions. On the ground under the nozzle trajectory, the highest and lowest droplet density were observed with the Twin Fan Standard (45.0 droplet cm−2) and Turbo TeeJet Induction (11.0 droplet cm−2) nozzles at 0.5 m s−1 wind speed, respectively. With the exception of the Turbo TeeJet, Turbo Twin Jet and Air Induction Turbo Twin Jet nozzles, a significant droplet density was exo-drifted up to 10 m distance when other nozzle types were used to spray at 7.5 m s−1 wind speed. The highest and the lowest ED50 values were obtained with the Turbo TeeJet Induction (9.84 g a. i. ha−1) and Twin Fan Standard (3.26 g a. i. ha−1) nozzles when clodinafop-propargyl was sprayed at 0.5 m s−1 wind speed, respectively. While, the highest and the lowest ED50 values were obtained with the Turbo TeeJet Induction (12.35 g a. i. ha−1) and Turbo Twin Jet (9.23 g a. i. ha−1) nozzles when clodinafop-propargyl was sprayed at 7.5 m s−1 wind speed, respectively. The Twin Fan Standard nozzle having the lowest endo-drift at wind speed authorized and the Turbo Twin Jet nozzle having almost low exo-drift at wind speed unauthorized were found to be an optimal nozzle to obtain an optimal clodinafop-propargyl potency against winter wild oat.