Effect of glycerol on spreading and drying of vision® droplets containing Silwet® L‐77: Relevance to rainfastness and herbicidal activity of glyphosate on trembling aspen (Populus tremuloides Michx.)

Abstract Literature information indicates that Silwet® L‐77 acted as a rainfastening adjuvant and provided increased herbicidal activity on quackgrass. However, previous results on trembling aspen were inconclusive, probably due to the high dosage rate (1.0 kg glyphosate/ha) used, or due to excessive spreading and rapid drying of droplets. This paper describes a laboratory study conducted in 1990 using a low dosage rate of 0.4 kg glyphosate/ha to optimize the concentrations of a humectant adjuvant (glycerol), and a field study conducted in 1991 using the optimum concentration of glycerol to examine rainfastness and herbicidal activity of glyphosate under field conditions. The laboratory study involved application of Vision® (a formulation concentrate of glyphosate) droplets with and without Silwet and glycerol, onto trembling aspen leaf discs to determine the optimum spray mix based on maximum droplet spreading, drying time and rainfastness. The optimum spray mix (Vision + 0.15% of Silwet and 0.25% of gly...