Improving the effectiveness of aerial pesticide sprays

Thirty-eight aircraft setups were submitted in order to have droplet size and drift analyses performed. Four of the eleven insecticides predicted D(v0.5)s were in the 351-400 mu m range. Seven of the herbicide setups had predicted D(v0.5)s in the 205-250 mu m range, while ten D(v0.5)s were > 351 mu m. Five of the ten predicted D(v0.5)s were between 386 and 413 mu m. Twelve different herbicides were reported as having been applied with aircraft setups that had predicted D(v0.5)s between 386 and 413 mu m. A summary of the prior swath deposit data indicated that the percent recovery generally increased as the D-v0.5 increased. The magnitudes of the deposits on inert targets and cotton leaves appeared to be about equal for a given D-v0.5. The correlation coefficient between the "percent of the spray volume in droplets : 100 mu m and <= 200 mu m in diarneter" was 0.983. This result is consistent with prior results and indicates that either 100 or 200 mu m can be effectively used as the upper limit when studying the "small droplet" component in sprays. We found several similarities or differences in the "small droplet" components based on data from different atomization tests. According to one set of atomization models, agricultural aircraft will be limited to about 225 km/h (i.e., 140 mph) in order to produce a 400 mu m D-v0.5 spray when using currently available nozzles and water plus one or more pesticides. The extremes of the predicted drift deposits for 38 agricultural aircraft setups were over 30-fold apart.