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9 December 2020 Influence of hard water on 2,4-D formulations for the control of dandelion
Geoffrey P. Schortgen, Aaron J. Patton
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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

© The Author(s), 2020. Published by Cambridge University Press on behalf of the Weed Science Society of America.
Geoffrey P. Schortgen and Aaron J. Patton "Influence of hard water on 2,4-D formulations for the control of dandelion," Weed Technology 35(3), 371-379, (9 December 2020).
Received: 28 September 2020; Accepted: 20 November 2020; Published: 9 December 2020

emulsifiable concentrate
hard water
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