Influence of hard water on 2,4-D formulations for the control of dandelion

• Published in: Weed technology 2021-06, Vol.35 (3), p.371-379
• Main Authors: Schortgen, Geoffrey P., Patton, Aaron J.
• Format: Article
• Language: English
• Subjects: 2,4-D; Acids; amine; antagonism; Auxins; Calcium carbonate; Choline; Cropping systems; Diethanolamine; emulsifiable concentrate; Emulsifying agents; emulsion; Emulsions; ester; Experiments; Formulations; Greenhouses; hard water; Herbicides; Horticulture; Ingredients; Isooctyl ester; Loam soils; Proprietary; Salt; Salts; Water chemistry; Water hardness; water-insoluble; water-soluble
• ISSN: 0890-037X; 1550-2740
• DOI: 10.1017/wet.2020.135

The herbicide 2,4-D is used in a variety of cropping systems, especially in grasses because it is a selective postemergence broadleaf herbicide. However, the most common formulation (2,4-D dimethylamine) is antagonized when mixed in hard water. The objective of this research was to determine which formulations of 2,4-D or premixes of various formulations of synthetic auxin herbicides are subject to hard water antagonism. Formulations surveyed for hard water antagonism in the first experiment included 2,4-D dimethylamine, 2,4-D diethanolamine, 2,4-D monomethylamine, 2,4-D isopropylamine salt, 2,4-D choline salt, 2,4-D isooctyl ester, and 2,4-D ethylhexyl ester. Synthetic auxin formulation types in the second experiment included water-soluble, emulsifiable concentrates and emulsion-in-water. All formulations were mixed with both soft and hard water (600 mg CaCO3 L-1) and applied to dandelions to determine whether antagonism occurred in hard water. Water-soluble (amine and choline) 2,4-D formulations were antagonized by hard water, but water-insoluble (ester) 2,4-D formulations were not antagonized. Similar results were found by formulation type with water-soluble synthetic auxin premixes antagonized but emulsifiable concentrates not antagonized. Furthermore, water-soluble salt formulations were not antagonized when formulated in premixes with other synthetic auxin herbicides as an emulsion-in-water. This research demonstrates that all 2,4-D water-soluble formulations and water-soluble premixes with phenoxycarboxylic acid herbicides are subject to hard water antagonism. Formulations of 2,4-D containing emulsifying agents protect against antagonism by the water-insoluble nature of ingredients in their formulation. Nomenclature: 2,4-D; dandelion; Taraxacum officinale G.H. Weber ex Wiggers; MCPP; MCPA