Efficacy of herbicidal ionic liquids and choline salt based on 2,4-D

Five quaternary ammonium salts with the 2,4-dichlorophenoxyacetate [2,4-D] anion were synthesized and their physicochemical properties and efficacy against weeds was investigated. The following cations were used in the synthesis: (2-hydroxyethyl)trimethylammonium [Choline], (2-chloroethyl)trimethylammonium [CC], cocotrimethylammonium [Arq], bis(2-hydroxyethyl)cocomethylammonium [Etq C] and bis(2-hydroxyethyl)methyloleylammonium [Etq 0]. Among them, four compounds: [CC][2,4-D], [Arq][2,4-D], [Etq C][2,4-D] and [Etq 0][2,4-D] were classified as herbicidal ionic liquids (HILs). Data from greenhouse studies showed similar or better efficacy of ionic liquids based on 2,4-D compared to commercial formulations of 2-ethylhexyl ester and dimethylammonium salt and also to choline salts which is recently marketed but in the mixture with glyphosate (Enlist Duo, Dow Agro-Sciences LLC). HILS with 2,4-D anion also showed excellent efficacy in field experiments. In this case, all tested HILs demonstrated several times higher efficacy compared to choline, dimethylammonium salts and 2-ethylhexyl ester. All the described results suggest that selection of an appropriate cation allows to control the physicochemical properties of studied herbicidal ionic liquids, which proved to have a significant impact on its biological activity. (C) 2017 Elsevier Ltd. All rights reserved.