ABSTRACT
84The role of adjuvants on droplet size spectra, deposit patterns, and dislodgable and penetrated residues of fenitrothion in conifer needles was studied following spray application of three aqueous formulations onto balsam fir seedlings under laboratory conditions and one aqueous and three oil-based formulations onto white spruce trees under field conditions. Spray was applied using spinning disc nozzles in both studies. Droplet size spectra and deposits were assessed using Kromekote cards and glass plates. Foliar residues were measured by gas-liquid chromatography (GLC). In both studies, the adjuvants used in the formulations imparted different volatilities to the spray media. The low-volatility formulations provided larger droplets and greater deposits; foliar residues were also correspondingly higher. The penetrated residues, however, remained the same, irrespective of the differences in the total foliar concentrations. Thus, the study indicated an upper limit for the partitioning capability of the chemical into the subsurface tissues. A comparative evaluation of the partitioning capability between the balsam fir seedlings and white spruce trees indicated a marked difference in the penetrated residues, in spite of the moderate differences observed in the dislodgable residues. This is probably due to the differences in the cuticular development of the two conifer species, or the age difference of the trees used, i.e., the young balsam fir seedlings vs. the moderately mature white spruce trees. These aspects require further investigation.
