 With placement (localised) spraying of broad spectrum pesticides, wind drift must be minimized, and considerable efforts have been made to quantify and control spray drift from hydraulic nozzles.Conversely, wind drift is also an efficient mechanism for moving droplets of an appropriate size range to their targets over a wide area with ultra-low volume (ULV) spraying.Himel (1974) made a distinction between exo-drift (the transfer of spray out of the target area) and endo-drift, where the active ingredient (AI) in droplets falls into the target area, but does not reach the biological target.