Use and mode of action of adjuvants for herbicides: A review of some current work

Abstract

The use of surfactants, mineral and vegetable oils, emulsifiers and fertiliser salts, such as ammonium sulfate, can greatly enhance the activity of foliage‐applied herbicides. Adjuvant‐herbicide interactions are reviewed with particular reference to the benefits, including dose reduction, enhanced and more consistent herbicide activity, and the nature of underlying mechanisms; the use and role of surfactants receive particular attention. Surfactants are used as activators in commercial formulations of many herbicides to improve their foliar absorption and ultimate biological activity. Current views on their influence are considered in relation to surface phenomena, solubilisation of non‐polar active ingredients, wax dissolution, cuticle penetration, preferential sites of penetration, membrane permeability and possible systemicity. The importance of a number of moderating factors (plant, chemical and environmental) is discussed in the light of current work, with particular regard to herbicide polarity, surfactant type, Hydrophile‐Lipophile Balance and critical micelle concentration. Current studies on the influence of nonionic polyoxyethylene surfactants of differing ethylene oxide (EO) content have underlined the importance of EO number to their activity.

Alkyl Ether Sulfate Improves Efficacy of Herbicides Against Common Goosefoot and Field Bindweed in Wheat

“…Bromoxynil belongs to the nitrile family and inhibits photosynthesis at PS-II. Different types of adjuvants (surfactants, oils, emulsifiers and fertilizer salts such as ammonium sulfate) have been found to enhance the activity of various foliar-applied herbicides against weeds (Kirkwood, 1993). Bryan et al (2003) showed a differential increase in glyphosate absorption by two weed species (common lambsquarters and velvetleaf) by addition of ammonium sulfate as an adjuvant.…”

Fractioning of an ethoxylated soybean oil adjuvant and studies on the potency of the fractions in combination with bromoxynil octanoate and sulfonylurea herbicides

“…The amount of AI reaching the target site determines the efficacy of an herbicide and depends on various factors like herbicide retention on the leaf surface, wetting of leaves, absorption, translocation, immobilisation, and detoxification in plants (Kirkwood 1993). Adjuvants are ingredients of almost all herbicide formulations and act as important tools to improve the technical quality of a herbicide required for application and/or to enhance the herbicidal efficacy (Green & Foy 2000).…”

pH foliar e deposição de gotas de pulverização em plantas daninhas aquáticas: Brachiaria mutica, Brachiaria subquadripara e Panicum repens

“…O uso de adjuvantes nas aplicações de herbicidas pode aumentar o espalhamento, a retenção e a penetração do ingrediente ativo pela superfície foliar, bem como reduzir o período mínimo sem chuva para que haja absorção do produto. O emprego desses aditivos pode promover consideráveis benefícios econô-micos e ambientais, devido à possibilidade de redução da dose do ingrediente ativo recomendada (Matuo et al, 1989;Kirkwood, 1993).…”