Selection of the Least Drifting Spray Nozzles for Pesticide Application to Protect Insect Pollinators

Highlights This study aimed to identify pesticide spray nozzles with low drift to protect insect pollinators. The size and speed of droplets from 17 nozzles were tested to estimate DV0.1, DV0.5, DV0.9, and % spray 150 µm. The nozzle entry orifice area affects the flow rate, and the ratio of nozzle entry/exit orifice area affects drift. All air induction nozzles, and AITTJ60-110025, appear to minimize drift. ABSTRACT. Pesticide exposure, including off-target drift, is troubling the thriving beekeeping industry in Mississippi. The selection of the least drifting spray nozzle(s) is one way to protect insect pollinators. The major goal of this study is to identify nozzles with low drift for pesticide spray applications. The specific objectives include (a) observing the size, speed, and flow rate data from seventeen broadcast nozzles; (b) estimating the proportion of spray volume with driftable size droplets; (c) estimating the size and speed relationships for all the nozzles; and (d) identifying the nozzles that are less likely to drift during pesticide applications. The flow rate for each nozzle was obtained using a SpotOn spray calibrator. The spray equipment was designed in-house to carry out the experiment. The droplet size and speed were measured via a VisiSize P15 image analyzer. The diameter and speed quantiles were calculated at the 10 th , 50 th , and 90 th volume percentiles. The proportion of spray volume with droplets 150 µm and 100 µm and the Sauter mean diameter (d 32 ) were also calculated. ANOVA tables corresponding to the results were also generated to identify the interactions between the nozzle, pressure, and height. The results suggest that the nozzle entry orifice area determines the nozzle flow rate and that the ratio of the nozzle entry orifice to the exit orifice affects the driftable spray volume. The air induction nozzles and nozzle AITTJ60-110025 appear to minimize off-target drift to protect pollinators. Drift guard nozzles DG8002, DG8003, DG8004, Turbo TeeJet nozzle TT11001 and the extended range nozzle AIXR11002 produce moderate driftable size spray volumes, while the remaining nozzles produce high drift. Given the scenario of chemical application and the target application rate, the results from this study can guide stakeholders in identifying the most suitable spray nozzle to minimize off-target drift, improve application efficiency, and protect insect pollinators. Keywords: Air induction, extended range, drift guard, pesticide spray, drift, spray droplet size, spray droplet speed.