The Washington orchard spray drift study: Lidar imaging of pesticide spray drift from an orchard airblast sprayer

摘要

We present laser remote sensing data of pesticide spray drift collected during orchard airblast applications of phosmet to a commercial apple orchard. These data were collected as part of a comprehensive spray drift field study. The lidar was a monostatic 355nm UV scanning lidar. By radially scanning just above and downwind of the sprayed apple trees from a vantage point in an adjacent field, we captured a sequence of near real-time images of the movement of an actual pesticide aerosol drift event over a range of nearly 300 meters. These lidar signals were interpreted qualitatively and depicted a phenomenon that was plume-like and highly influenced by changing wind direction both within and beyond the orchard canopy. Pesticide spray drift also exhibited formerly unexpected behavior such as: traveling down tree rows as within a street canyon; moving crosswind within the canopy before either lofting above the canopy or being channeled out along an upwind row of the orchard. These lidar observations document previously unobserved pesticide spray movement phenomena that challenge current regulatory approaches to estimating drift from orchard airblast spraying. Limitations of our lidar system were observed in the intermittent and, at times, discontinuous nature of our data. Suggestions are made for a more effective use of lidar technology to monitor spray drift.