Two Herbicides in a Single Compound: Double Salt Herbicidal Ionic Liquids Exemplified with Glyphosate, Dicamba, and MCPA

Herbicidal ionic liquids (HILs) have been demonstrated to have potential as highly effective herbicides that may also have different modes of action that their neutral precursors. Here, double salt herbicidal ionic liquids (DSHILs) containing at least two herbicidal anions selected from glyphosate, dicamba, or 4-chloro-2-methylphenoxyacetate (MCPA) paired with ammonium or phosphonium cations are reported along with their post-emergence herbicidal activity against several plant species, from both greenhouse and field study-based bioassays. The novel DSHILs were shown to integrate the advantages of two different herbicides into a single HIL, enhance herbicidal efficacy, and reduce the risk of weed resistance due to the various modes of action of the applied treatment. The formation of the DSHILs dramatically reduced melting points and modified the compound solubilities compared to the parent herbicides. Statistical analyses for the greenhouse efficacy tests demonstrated that DSHILs had significant positive differences against winter wheat (Triticum aestivum L.) and white mustard (Sinapis alba L.) as compared to commercial formulations. Biodegradability studies were also performed on selected DSHILs, and the compounds were found to be not readily biodegradable.