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Water conditioners have markedly enhanced the efficacy of glyphosate and glufosinate in spray systems using hard water. Cations that may be found in hard water include Al+++, Fe+++, Fe++, Ca++, and Mg++. They can bind to weakly anionic herbicides, resulting in decreased absorption of their complexes by plants. The growth regulator herbicides, 2,4-D and dicamba, are also anionic like glyphosate and thus could potentially benefit from the use of water conditioners. Effective water conditioners either serve as a source of ammonium ions that can outcompete the cations in hard water for the negative sites on the herbicide molecule or they act as chelators binding to the problem cations. The objective of this research was to determine whether either type of water conditioner influenced the efficacy of 2,4-D or dicamba applied in hard water. The dimethylamine salt of 2,4-D as well as an acid formulation were applied at sublethal dosage rates to velvetleaf and common lambsquarters in greenhouse studies. Dicamba was applied as the diglycolamine salt. The studies were conducted in the greenhouse with supplemental lighting and weed control was evaluated 7, 10, 14, and 21 days after herbicide application. The water conditioners increased the activity of all three herbicide formulations. The observed enhancement of efficacy was greatest with the 2,4-D dimethylamine. Enhancement of efficacy by the surfactant component was more readily observed on common lambsquarters than on velvetleaf. The beneficial effects of the water conditioners was greater for 2,4-D than for glyphosate.
AMADS, diammonium sulfate, dicamba, 2,4-D
Professor, Department of Plant, Soil, and Microbial Sciences, Michigan State Univ., East Lansing, MI
Research Associate, Department of Plant, Soil, and Microbial Sciences, Michigan State Univ., East Lansing, MI