Blowing in the Wind: Can a Field Drift Bioassay Be Replicated in a Wind Tunnel Using Atrazine as a Case Study?

High Resolution Image Download MS PowerPoint Slide A wind tunnel drift bioassay was conducted to assess whether such a facility could serve as an experimental analogue for field-scale experiments. Using atrazine (AAtrex 4L) as a test case, spray drift deposition, airborne interception, and corresponding biological effects on two sensitive plant species (cucumber and lettuce) were assessed and compared. Wherever possible conditions and experimental procedures were consistent, including conceptual design (rows of potted plants placed at 5, 15, 25, 35, and 45 ft [1.5, 4.6, 7.6, 10.7, and 13.7 m]), nozzles (TeeJet TTI11004), target windspeeds (>10 mph; >16 km/h), sampling devices (stainless steel discs and rods), biological assessment window (21 days post-application), endpoints (survival, biomass, and shoot length) etc. Overall, when trials were combined, the aggregate lowest observable effect distance (LOED) was 15-ft [4.6 m] and the aggregate no observable effects distance (NOED) was 25-ft [7.6 m], with cucumbers affected more than lettuce. These results are consistent with corresponding LOED and NOED values of 5-ft [1.5 m] and 15-ft [4.6 m] obtained from the field drift bioassay counterpart.