Published: Jan 2003
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The herbicide 2,4-D is an important herbicide at a global level. In 1999, the herbicide was ranked as the fifth herbicide in the United States regarding sales. The 2,4-D amine salts are generally not applied in combination with adjuvants. An effective and inexpensive adjuvant, either as built-in or as tank-mix adjuvant, can create a new product with benefits for the user and the environment. Such a product can be an alternative for the 2,4-D esters requiring emulsion-type formulations. The objective of this study is to investigate whether a review of published data, insight in the adjuvant-action and knowledge of the weed species may result in a list of adjuvant types being effective for 2,4-D amine salts. The lipophilicity of the 2,4-D molecule depends on the pH-dependent dissociation of the carboxylic group. Both hydrophilic and lipophilic adjuvants can be effective for 2,4-D amine salts. It will be discussed in how far this is related to the pH- dependent ionic character of 2,4-D. Ion-pair formation by association of the 2,4-D anion with a cationic counter ion as a tool for improving herbicide performance will be discussed. Calcium ions in the water used as carrier may reduce the performance of 2,4-D. It will be discussed in how far adjuvants may overcome this antagonistic effect of calcium.
2,4-D, 2,4-dichlorophenoxy acetic acid, 2,4-D amine, adjuvant, surfactant, pH, ion-pair
de Ruiter, H
Director, SURfaPLUS R&D bv, AA Wageningen,