An evaluation of physical properties, droplet spectra, ground deposits and soil residues of aerially applied aminocarb and fenitrothion emulsions in conifer forests in New Brunswick

Abstract

Abstract A comparative evaluation of physical properties, spray droplet spectra, ground deposits and soil residues was made for two aminocarb and two fenitrothion emulsions, following aerial application in New Brunswick, at dosage rates of 70 g active ingredient (AI) in 1.5 L/ha and 210 g AI in 1.5 L/ha, respectively. The aminocarb emulsions were less viscous and more volatile than those of fenitrothion. However, variations in droplet size spectra, number and volume median diameters were minimal among the four formulations, although significantly more droplets/cm2 and higher deposits in g AI/ha were obtained for the most viscous fenitrothion mixture. All emulsions showed similar surface tension values and therefore, the contribution of surface tension to droplet size spectra could not be demonstrated. All emulsions produced very low soil residues, but those of aminocarb were lower than those of fenitrothion. However, when differences in the dosage rates were taken into account, the residues were somewhat similar for all formulations. The aminocarb residues disappeared from the soil within 12 h post‐treatment, whereas those of fenitrothion persisted for at least 10 days. These differences were neither due to the presence of heavy or light oils in the emulsions nor to the surfactant concentrations; but were due to the higher initial deposits of AI on the soil.