A Proposed Mode of Action of Oil-Based Formulations of a Microbial Herbicide

Abstract

Formulation of some microbial herbicides in emulsions of vegetable oil can significantly reduce their dependency on long dew periods to allow infection and control of the host weed. Examination of leaves of Viola arvensis , by a range of microscopy techniques, after spraying with an oilin-water emulsion formulation of the potential microbial herbicide Mycocentrospora acerina , suggests that the effect arises as a result of inversion of water into both oil droplets on the leaf surface and oil that penetrates into the leaf tissue. This oil probably mixes with aqueous components from the leaf tissue and, in doing so, forms an invert emulsion. Wesuggest that this supplies the water required by the fungus to initiate and sustain growth so that infection can result.