Off-target pesticide movement: a review of our current understanding of drift due to inversions and secondary movement

Abstract

Pesticide drift has been a concern since the introduction of pesticides. Historical incidences with off-target movement of 2,4-D and dichlorodiphenyltrichloroethane (DDT) increased our understanding of pesticide fate in the atmosphere related to aerial pesticide applications. More recent incidences with dicamba have brought to light gaps in our current understanding of aerial pesticide movement following ground pesticide applications. In this paper, we review current understanding of inversions and other weather and environmental factors that contribute to secondary pesticide movement and highlight questions that need to be addressed. Factors that influence volatility and terminology associated with the atmosphere, such as cool air drainage, temperature inversions, and radiation cooling will be discussed. We also present literature that highlights the need to consider the role(s) of wind in secondary drift in addition to the role in physical drift. With increased awareness of pesticide movement and more herbicide-resistant traits available than ever before, it has become even more essential that we understand secondary movement of pesticides, recognize our gaps in understanding, and advance from what is currently unknown.

Evaluation of potassium borate as a volatility-reducing agent for dicamba

“…Furthermore, variability in dicamba detected within a treatment decreased as KBo concentration increased, an indication of less environmental influence on the volatilization of the herbicide in the presence of the VRA. In other research, it has been noted that the detection of dicamba can be quite variable because of differences in environmental conditions during experiments (Behrens and Lueschen 1979;Bish et al 2021;Mueller et al , 2019a. Despite the absence of an established threshold for in-air concentrations of dicamba as it pertains to a specific degree of soybean injury, findings suggest KBo at 0.025 M or higher concentrations show dicamba volatilization is significantly reduced, likewise resulting in less risk for off-target soybean injury.…”

“…The full launch of the Xtend® technology in 2017 undoubtedly led to a record number of complaints associated with extensive landscape damage to sensitive soybean from off-target movement of dicamba, specifically in areas where the adoption of DR crops was greater (Bish and Bradley 2017;Bish et al 2020;Bradley 2017;Hager 2017;Steckel 2017). Although there are many avenues by which herbicides move off-target and injure nearby vegetation, most of the injury to soybean from labeled applications of dicamba is suspected to be the result of secondary movement via volatilization or particle suspension within temperature inversions, which likely explains the landscape nature of the damage (Bish et al 2019).…”

Evaluating methods and factors that affect dicamba volatility

“…Physical drift is the deviation of the trajectory of the particles (droplets) released by the spraying process that do not reach the target. This movement outside the target area is mitigated by the correct use of application technology, such as correct choice of spray tip, droplet size, working pressure, boom height and equipment speed, in addition to considering the ideal meteorological conditions during spraying (Bish et al, 2021).…”

Evaluating the Spectral Response and Yield of Soybean Following Exposure to Sublethal Rates of 2,4-D and Dicamba at Vegetative and Reproductive Growth Stages

“…In the first few years following the commercialization of dicamba-resistant soybean (in 2016), thousands of off-target dicamba injury complaints were reported to state departments of agriculture throughout the Midwest and Mid-South regions of the United States. Researchers estimated these complaints represented millions of hectares of injury to sensitive plant species [7,8]. It was well known prior to the release of the dicamba-resistant trait that many plants, including soybean, are highly sensitive to exceptionally low rates of dicamba [9].…”