Further studies with additives: Effects of phosphate esters and ammonium salts on the activity of leaf‐applied herbicides

Abstract

AbstractThe phytotoxicity of glyphosate applied to the leaves of dwarf bean (Phaseolus vulgaris L.) and several woody species was enhanced by mixed butyl acid phosphates (BAP, a technical mixture of dibutyl hydrogen and butyl dihydrogen phosphates) or ammonium sulphate. Tributyl phosphate, or the mixed sodium salts of BAP, similarly increased the activity of aminotriazole. This type of effect did not occur with mixtures of this herbicide and inorganic ammonium salts or the ammonium salts of BAP. Neither phosphate esters nor ammonium salts enhanced the activity of paraquat. Ammonium BAP was more effective than sodium BAP as an activator for leaf‐applied picloram or MCPA salts. While phosphate esters and ammonium salts probably have separate modes of action they have similar effects in mixture with many water‐soluble herbicides and for many purposes may be regarded as alternative activators. Ammonium salts, particularly ammonium sulphate, have obvious advantages because of their cheapness and low mammalian toxicity.