Abstract

Dicamba is a herbicide with a moderate volatility profile. Such volatility behavior can be significantly diminished with formulation technology and volatilization reducers. The objective of this study was to quantify the volatility potential of dicamba diglycolamine salt (DGA) in a standalone application or in tank mixture with glyphosate (potassium salt) (GK), with and without volatilization reducer (acetic acid—VaporGrip®) from different surfaces. The combination of these products was applied on four different surfaces (glass slides, corn straw, and dry and moist sandy soil) with three replications, and the experiment was duplicated. The application was performed indoors with an automated sprayer. After application, targets were positioned in cartridges containing two filters in series. Cartridges were placed in a vapor collection system that consisted of a chromatographic oven with constant temperature of 40 °C attached to a vacuum pump for 24 h. After this period, liquid samples were obtained from an extraction procedure of filters and surfaces, which corresponded to the volatilized and deposited portions of the herbicides, respectively. The samples were analyzed by liquid chromatography–tandem mass spectrometry (LC-MS/MS). The use of this method provided a rapid and consistent evaluation, in which the treated surface exerts a direct influence on the amount of volatilized dicamba. The mixture of dicamba and glyphosate solutions exhibited different volatility profiles as a function of the treated surfaces. The DGA applied alone had the largest level of volatility when applied on moist soil and the lowest level of volatility in dry soil and straw. The DGA with GK had volatilities similar in dry soil, wet soil and straw. The volatility reducer in the tank mixture was effective in reducing DGA dicamba volatilization, regardless of the sprayed surface and the tank mixture, making the application of dicamba safer from the volatilization standpoint.

Highlights

  • The herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) belongs to the benzoic acid chemical group, and is a synthetic auxin [1]

  • The objective of this study was to quantify the volatilization of standalone diglycolamine salt (DGA) dicamba or in mixture with glyphosate, with and without the volatilization reducer from different surfaces

  • VG), the DGA volatilizations from dry soil and straw were similar. These results show that when the VG is used with DGA, the presence or absence of straw, or the condition of soil surface moisture, is not important, and the levels of volatility are similar

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Summary

Introduction

The herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) belongs to the benzoic acid chemical group, and is a synthetic auxin [1]. This postemergence herbicide has been used for a long time to control broadleaf weeds in winter cereals and in pastures in several countries around the globe. The Brazilian regulatory agency (CTNBio) has de-regulated dicamba-resistant soybean, corn and cotton in recent years [2,3]. The commercialization in Brazil of such crop trait products is planned to start in the 2021/2022 season The introduction of such technology will serve as an important tool to sustainably manage herbicide-resistant weeds, and to protect the technology and selective herbicide chemistry currently available in the Brazilian market

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