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United States Department of Agriculture

Agricultural Research Service

Research Project: Reduction of Drift and Timing of Spray Application for Protection of Bees During Temperature Inversions

Location: Crop Production Systems Research

Project Number: 6066-22000-079-11-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 9, 2013
End Date: Sep 8, 2018

To evaluate whether ground spraying during a temperature inversion causes significant off target drift vs. spraying under non-inversion conditions. This will determine the time window under which spraying can occur without deleterious drift consequences, possibly allowing application during periods not detrimental to bees pollinating. If a sprayer/nozzle combination can be found to safely spray under inversion conditions, this might allow maximum flexibility for spraying when bees are out of the field.

A ground spraying test will be conducted comparing both a hooded sprayer (likely to confine spray) and conventional high-boy sprayer under both unstable atmospheric conditions favorable for spraying and stable atmospheric conditions. The latter is associated with temperature inversions and normally considered to be unfavorable for long distance drift potential at dusk. A single spray release height will be used for both sprayers comparing both Teejet Turbo Twin-Jet® and conventional XR® Extended Range low drift nozzles, as these two nozzle types have shown good canopy penetration and favorable low drift characteristics. Nozzle type sequence and sprayer selection will be randomized. Three complete replications of the experiment will be conducted on each side of the time temperature inversions take place (one set of tests under inversion conditions; one without). Spray samplers will be placed on the ground at nine locations across the spray swath and five locations downwind. Tank mix will consist of a water and SylTac® surfactant mixture and Rubidium Chloride (RbCl) as an inert tracer. Spray will be collected on Mylar sheets for subsequent analysis of RbCl; water sensitive paper (WSP) to obtain droplet size and droplet area/unit card area. RbCl concentration will be analyzed using a Perkin Elmer Atomic Absorption Spectrometer and droplets from WSP will be scanned using a JVC camera, frame grabber, and using SigmaScan droplet scanning macros. A portable meteorological tower with calibrated Kestrel® 4500 weather units placed at three heights will be installed on-site and will be used to obtain wind and air temperature data for calculation of real-time atmospheric stability via Bluetooth telemetry. These data will be used to determine when to begin the set of runs under inversion conditions. Previous experiments have indicated increased statistical precision by blocking runs on time of day to better account for environmental factors, so both the ‘inversion’ and non’inversion’ experiments will be conducted in close temporal proximity.

Last Modified: 09/20/2017
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