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Evaluation of drift reduction adjuvants via biological injury on soybeans from simulated dicamba drift in a low-speed wind tunnel

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2022 ASABE Annual International Meeting  2200653.(doi:10.13031/aim.202200653)
Authors:   Aszhia K. Albrecht, Elizabeth R. Alonzi, Anderson Weber, Joshua J. Skelton, Steven A. Fredericks
Keywords:   Adjuvants, Dicamba, Drift, Epinasty, Soybean Injury, Spray Flux, Wind Tunnel

Abstract. The primary method for application of post-emergent crop protection products is via spray. While an efficient method, it introduces the potential for off-target migration of the applied product via droplet entrainment in ambient wind, known as drift. This drift can contribute to a lack of efficacy in the target field, contamination of adjacent waterways, increased pesticide resistance of weeds, and injury of non-target plants. Numerous techniques exist to mitigate drift and have historically been evaluated in field trials or through secondary measurements, such as droplet size distribution. Herein a low-speed wind tunnel was used to simulate spray drift. Several field representative tank mixtures including commercially available dicamba and glyphosate formulations, water conditioners, volatility reduction adjuvants, and drift reduction adjuvants (DRAs) were applied. Disodium fluorescein was added as a tracer to enable quantitative measurement of spray flux. Downwind of the spray, nonresistant soybeans were placed at 3 m intervals and exposed to 1 s spray duration with a wind speed of 4.5 m/s, then removed to a greenhouse for visual injury observation over a 14 day period. Additionally, sampler cards were placed in each row of soybeans to collect drifting spray and analyzed to determine the corresponding spray flux. It was found that the measured spray flux correlated well with observed soybean injury, and the use of a dedicated DRA had the lowest observed drift of all treatments, while combination DRA + water conditioner convenience products had lower observed drift than the herbicides alone.

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