Effect of tank-mixed blended green adjuvants on glyphosate efficacy in four winter crop weed species

摘要

The effect of four 'green' blended adjuvants on the effectiveness of glyphosate on the grass species Alopecurus myosuroides, Lolium rigidum and Avena fatua and the broad-leaved species Chenopodium album was studied. The adjuvants used in the experiments were alkyl-polysaccharide derivatives and several by-products derived from the food industry, including modified lecithins. The parameters of the ED50, spray retention, contact angle, leaf coverage, foliar uptake and translocation were compared. The effect on ED50 values of the presence of adjuvants in the spraying solution varied, depending on the species. All the adjuvants tested failed to increase glyphosate effectiveness in L. rigidum, but promising results were obtained for the other three species, where one (A. myosuroides) to four (A. fatua) adjuvants showed better results than unamended controls. Retention, contact angle and absorption/translocation parameters studied could not individually explain the enhancement effect observed in some of the mixtures. However, there was a relationship between high retention values and glyphosate effectiveness, which was modulated by the presence/absence of high contact angle droplets, resulting in thick, discrete glyphosate spots, rather than thin leaf-covering herbicide layers. The analysis of these two variables may be an easy way to predict the effectiveness of herbicide formulations, by presenting concentration-dependant uptake patterns.