To estimate safe downwind distances (i.e. buffer zone widths) for temporary ponds from ULV-treatments with current locust insecticides, experimental trials with two ground-based sprayers, the hand-held Micro-Ulva® and the vehicle-mounted Ulva-Mast® X15 Mark I, were conducted with fenitrothion (Sumithion® L50) as a model insecticide. Deposition profiles for each sprayer were obtained for a single- and a five-track application. Water from glass containers exposed to the multiple-track treatments was used for laboratory bioassays with the backswimmer Anisops sardeus (Hemiptera, Notonectidae). Buffer zone widths were defined as the distance at which 48 h-mortality in the bioassays was 20% or less. The deposition profiles from the multiple-track applications were subsequently used to estimate buffer zone widths for 11 insecticides currently used in desert locust control. It was concluded that at moderate wind speeds (2-4 m/s), a buffer zone width of 200 m for the Micro-Ulva and 400 m for the Ulva-Mast will, in general, be safe enough to avoid side-effects from any of these insecticides on sensitive aquatic invertebrates in temporary ponds. (C) 2000 Elsevier Science Ltd.