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

Abstract

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.

Synthesis and Structure–Property Relationships in Herbicidal Ionic Liquids and their Double Salts

“…Recently, a new group of DSHILs consisting of two herbicidal ions has been introduced . The combination of a nonselective herbicide (glyphosate) mixed with a synthetic auxin (MCPA or dicamba) exhibited selective activity towards dicotyledonous weeds.…”

“…This approache liminates also the necessity of using agricultural additives, such as adjuvants (often recommended for commercial crop protection agents), with ap otentially negative environmental impact owing to the less restrictive procedures of their registration as commercial products. Therefore, novel methods of HIL synthesis utilizingv arious herbicides including glyphosate, [10] MCPA, [11] 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP), [9,12] 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB), [13] 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP), [14] bentazone, [15] clopyralid, [16] fomesafen, [17] picloram [18] and sulfonylurea derivatives (e.g. metsulfuron-methyl) [19] have been proposed.Further advances in this field have resulted in the incorporation into HILs of nonconventional herbicidal anions of natural origin [20] or cations exhibitinga nother type of biological activity,s uch as plant growth inhibition.…”

“…Recently,anew group of DSHILs consisting of two herbicidal ions has been introduced. [10] The combination of an onselective herbicide (glyphosate) mixed with as ynthetic auxin (MCPA or dicamba) exhibited selective activity towards dicotyledonous weeds. In this study,w ef ocused on the preparation of two homologous series of HILs consisting of structurally different herbicidal anions (MCPAa nd dicamba) followed by their combination to obtain DSHILsc omprising two herbicides characterized by the same mode of action.T his approach is often appliedb ym anufacturerso fc ommercial formulations (e.g.…”

Third-generation ionic liquids with N-alkylated 1,4-diazabicyclo[2.2.2]octane cations and pelargonate anions

“…The rst herbicidal ionic liquids (HILs), which incorporated MCPA and 2,4-D, were reported in 2011 and their high herbicidal activity as well as the ability to regulate the toxicity of the herbicide by selecting an appropriate cation was highlighted. 8 To date, HILs with the following herbicides in the anion structure have been described in the literature: 2,4-DP, 12 MCPB, 13 MCPP, 14 dicamba, 15 fomesafen, 16 clopyralid, 17 bentazone, 18 glyphosate, 19,20 metsulfuron methyl, 21 nicosulfuron, 9 nonanoic acid 22 and picloram. 23 The low volatility, which is characteristic for HILs, allows limiting the negative health effects during the application of the product.…”

Ammonium bio-ionic liquids based on camelina oil as potential novel agrochemicals

“…6) a novel group of ILs called herbicidal ionic liquids (HILs) which comprise a herbicidal anion was introduced. Currently there are literature reports regarding HILs based on the following herbicides: 2,4-D, 7 MCPA, 6 MCPB, 8 MCPP, 9 dichlorprop, 10 dicamba, 11,12 clopyralid, 13 fomesafen, 14 bentazon, 15 glyphosate, 16,17 metsulfuron methyl, 18 nonanoic acid 19 and picloram. 20 The combination of two different types of biological activity is also known to date, as exemplied by dual function ILs which function as both herbicides and growth regulators.…”