Effects of sprayer operating parameters on airborne drift from citrus air-carrier sprayers

Florida citrus is mostly sprayed with various types of air-carrier sprayers. These sprayers differ substantially in design features and are normally operated at different volume rates and ground speeds, during day and night applications.  The main objective of this study was to characterize drift potential (not total drift) of several commonly used citrus sprayers when operated under typical application conditions (different operating variables).  Drift potential of the applications was assessed by capturing samples of airborne spray droplets with two high-volume air samplers, positioned above tree canopies at two sides of the spray course.  For most applications, higher spray volumes (larger droplets) showed significantly reduced drift potential than lower volumes. Higher ground speed appeared to have more drift potential compared to lower speed but the effect of speed was not significant. Nozzles with comparatively lower flow rates (smaller droplets) were generally more drift-prone than the ones with higher flow rates (larger droplets) and spray from the upper nozzle bank had higher drift potential than spray from lower nozzles. These results are comparative and could show the importance of optimizing spray variables to reduce drift from typical citrus applications. Keywords: s pray drift, spray volume rate, sprayer ground speed, air sampler, fluorometry