Droplet and Deposit Patterns of One Pseudoplastic and Three Newtonian Spray Mixtures Following Spray Application Under Laboratory Conditions

Abstract

A pseudoplastic spray mixture was prepared from fenitrothion, polymeric adjuvants and humectants. Three Newtonian spray mixtures were prepared, one each from fenitrothion, aminocarb and mexacarbate respectively, using oils, surfactants and cosolvents. The spray mixtures were sprayed over potted seedlings of balsam fir using a spinning disc atomizer, at an application rate of 1.5 L/ha. Aminocarb and mexacarbate were each sprayed at 70 g active ingredient (AI)/ha, whereas fenitrothion, at 210 g AI/ha. Spray droplets were sampled with Kromekote® cards and deposits were collected on glass plates. Foliar droplets were counted and pesticide concentrations were measured by gas-liquid-chromatography. Physical properties measured were: viscosity-shear rate relationship, surface tension and volatility. The data indicated that the presence of the polymeric adjuvants imparted pseudoplastic behavior to the spray medium. Because of this, the mixture provided a markedly larger droplet size spectrum and much greater deposit concentrations of the insecticide both on conifer foliage and on the sampling units.