Effect of formulation properties on ground and foliar deposits of two insecticides in flushed and one year-old balsam fir needles following aerial application

A study was conducted in 1985 in Newfoundland to investigate the interrelationships between the physical properties of spray formulations, droplet‐size spectra and deposits on ground sampling units, and deposits on flushed and one‐year‐old balsam fir foliage following aerial application of aminocarb and fenitrothion at different dosage rates, but using the same volume rates. The fenitrothion formulations were pseudoplastic, because of the presence of polymeric ingredients, and provided higher deposits on the ground sampling units and on foliage than the aminocarb formulations, which were nearly Newtonian. At similar dosage rates, the ground deposits of fenitrothion were about twice those of aminocarb, whereas the corresponding foliar deposits were about 6 to 8 times higher than those of aminocarb, suggesting possible advantages of pseudoplastic formulations in providing optimum droplet sizes for enhanced deposition on balsam fir needles. The foliar deposits generally showed an increase when the dosage rates of the two insecticides were increased. Deposits in flushed foliage were slightly higher than those in mature foliage, probably due to the location of the flushed needles at the extreme periphery of the tree canopy.