Identification of environmental factors that influence the likelihood of off‐target movement of dicamba

Oseland, Eric; Bish, Mandy D.; Steckel, Larry; Bradley, Kevin W.

doi:10.1002/ps.5887

Cited by 29 publications

(39 citation statements)

References 40 publications

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“…BASF has introduced the N,N-Bis-(aminopropyl) methylamine (BAPMA) formulation of dicamba (Hager 2017), whereas Monsanto introduced a diglycolamine (DGA) salt of dicamba that includes a pH modifier (Hemminghaus et al 2017;Macinnes 2017). At a soil pH <6.5, there was no difference in soybean bioassay plant response between the DGA formulation and the newer dicamba formulations (Oseland et al 2020).…”

Section: Introductionmentioning

confidence: 85%

Dicamba emissions under field conditions as affected by surface condition

Mueller

Steckel

2020

Weed Technol

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The evolution and widespread distribution of glyphosate-resistant broadleaf weed species catalyzed the introduction of dicamba-resistant crops that allow this herbicide to be applied POST to soybean and cotton. Applications of dicamba that are most cited for off-target movement have occurred in June and July in many states when weeds are often in high densities and at least 10-cm or greater at the time of application. For registration purposes, most field studies examining pesticide emissions are conducted using bare ground or very small plants. Research was conducted in Knoxville, TN in the summer of 2017, 2018, and 2019 to examine the effect of application surface (tilled soil, dead plants, green plants) on dicamba emissions under field conditions. Dicamba emissions after application were affected by the treated surface in all years, with the order from least to most emissions being dead plants < tilled soil < green plant material. In fact, dicamba emissions were > 300% when applied to green plants compared to other surfaces. These findings suggest that dicamba applications made to bare ground will likely underestimate what may occur under normal field use conditions when POST applications are made and the crop canopy or weed groundcocver is nearly 100% green material. A potential change to enhance the accuracy of current environmental simulation models would be to increase the theoretical findings to allow for the effect of green plant material on dicamba emissions under field conditions.

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Section: Introductionmentioning

confidence: 85%

Dicamba emissions under field conditions as affected by surface condition

Mueller

Steckel

2020

Weed Technol

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“…The potential for glyphosate to affect certain, but not all, synthetic auxin herbicides evaluated was proactively addressed by comparisons between the levels of glyphosate for each synthetic auxin, experiment, and application time-of-year combination (data not shown), which confirmed the results of the ANOVA that glyphosate had no impact on soybean injury. These results likely also were influenced by the pH of the soil used in flats at the research site (pH, 6.6); more acidic soils (pH 4.3 and 5.3) have been demonstrated to further contribute to volatility in low-tunnel volatility experiments (Oseland et al 2020).…”

Section: Low-tunnel Field Volatility Experimentsmentioning

confidence: 96%

“…Soybean injury was assessed visually on a scale from 0 to 100 (Andersen et al 2004;Behrens and Lueschen 1979) 28 d after treatment (DAT; when injury was most apparent), where 0 represents no injury and 100 represents dead plants, similar to previous work (Egan and Mortensen 2012;Jones et al 2019b;Oseland et al 2020). Soybean injury included leaf crinkling, malformation, and cupping of trifoliates that had formed after exposure to treated flats.…”

Section: Low-tunnel Field Volatility Experimentsmentioning

confidence: 99%

“…Visual injury is a commonly used method to quantify soybean injury from volatility (Behrens and Lueschen 1979;Egan and Mortensen 2012;Oseland et al 2020;Sciumbato et al 2004a;Sciumbato et al 2004b;Soltani et al 2020). The two meta-analyses on dicamba volatility focused on visual injury and soybean yield (Egan et al 2014;Kniss 2018).…”

Section: Low-tunnel Field Volatility Experimentsmentioning

confidence: 99%

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Spray solution pH and soybean injury as influenced by synthetic auxin formulation and spray additives

et al. 2020

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Use of synthetic auxin herbicides has increased across the United States Midwest following adoption of synthetic auxin-resistant soybean traits in addition to extensive use of these herbicides in corn. Off-target movement of synthetic auxin herbicides such as dicamba can lead to severe injury to sensitive plants nearby. Previous research has documented effects of glyphosate on spray solution pH and volatility of several dicamba formulations, but our understanding of the relationships between glyphosate and dicamba formulations commonly used in corn and for 2,4-D remains limited. The objectives of this research were to i) investigate the roles of synthetic auxin herbicide formulation, glyphosate and spray additives on spray solution pH, ii) assess the impact of synthetic auxin herbicide rate on solution pH, and iii) assess the influence of glyphosate and application time of year on dicamba and 2,4-D volatility using soybean as bioindicators in low-tunnel field volatility experiments. Addition of glyphosate to a synthetic auxin herbicide decreased solution pH below 5.0 for four of the seven herbicides tested (initial pH of water source = 7.45 to 7.70). Solution pH of most treatments was lower at a higher application rate (4× the labeled POST rate) than the 1× rate. Among all treatment factors, inclusion of glyphosate was the most important affecting spray solution pH; however, the addition of glyphosate did not influence Area Under the Injury over Distance Stairs (AUIDS; p=0.366) in low-tunnel field volatility experiments. Greater soybean injury in field experiments was associated with high air temperatures (maximum >29 C) and low wind speeds (mean 0.3 to 1.5 m s-1) during the 48-h period following treatment application. The two dicamba formulations (diglycolamine with VaporGrip® and sodium salts) showed similar levels of soybean injury for applications that occurred later in the growing season. Greater soybean injury was observed for dicamba than 2,4-D treatments.

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“…However, reported damage was still extensive (Figure 1) Bradley 2017b;Steckel 2017). In 2017, off-target movement of dicamba resulted in 2,708 dicamba-related injury investigations by state departments of agriculture (Figure 1; Oseland et al 2020). During this same year, state extension weed scientists estimated that approximately 1.5 million ha of soybean were reported to be injured by dicamba in the United States (Bradley 2017b).…”

Section: Postemergence Dicamba Applications To Soybean and Cottonmentioning

confidence: 99%

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

2020

Self Cite

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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.

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Identification of environmental factors that influence the likelihood of off‐target movement of dicamba

Cited by 29 publications

References 40 publications

Dicamba emissions under field conditions as affected by surface condition

Dicamba emissions under field conditions as affected by surface condition

Spray solution pH and soybean injury as influenced by synthetic auxin formulation and spray additives

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

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