Effect of Non-Volatile Rate on Spray Drift Potential: Field Study Validations of Model Predictions

by

Andrew Hewitt

Contact: Dr. Andrew Hewitt   e-mail: a.hewitt@uq.edu.au

Summary:

The AgDRIFT and AGDISP spray deposition models are being used in the development of no-spray buffer zones in several countries.  These models show that operational factors such as droplet size and maximum wind speed can be specified on pesticide labels for spray drift management.  Adjuvants and other non-volatile components of tank mixes can also reduce spray drift potential according to model runs; however, these effects have not been fully validated in field studies.  The present paper describes wind tunnel and field drift studies conducted to validate the model handling of non-volatile components and evaporation rates.  Tank mixes containing with 0, 1, 10 and 100% esterified seed oil were sprayed using an aircraft under typical field application conditions.  Tracer dyes were included in the sprays for recovery following collection on various samplers.  Spray drift was assessed as deposition on flat cards at various distances downwind of the application areas, and as deposition/ impaction on monofilament lines placed on vertical towers.

This presentation reports on the field trial data and the wind tunnel results.  Field deposition and airborne spray data are compared against predicted data from the spray drift models.  The field data agree well with the model trends, supporting the suggestion that increasing the non-volatile rate of the applied tank mix may significant reduce far-field off-target deposition rates.

Manuscript not available online; please contact author for manuscript information.

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