Within-canopy Spray Distribution from Fixed-wing Aircraft

Abstract

We have evaluated two approaches to improve spray deposition within crop canopies from insecticide applications with fixed-wing aircraft. Both approaches involve increasing air velocity and turbulence in the crop canopy as a result of increased wake intensity and are expected to result in increased spray deposits within the canopy. One approach was to increase wake intensity with slower airspeed than normally used. The second approach was to increase wake intensity with a modified boom equipped with Chimavir winglets. Spray deposits were measured from an agricultural aircraft with a conventional boom operated under normal conditions. Spray deposits were also measured from the same aircraft with boom and operational conditions modified to increase wake intensity. Results of deposit measurements from leaf washes and water-sensitive paper, both on the top and bottom of leaves, at the top and midway down in the crop canopy, show that a high percentage of spray is deposited on the top of leaves. The treatments with higher wake intensity increased deposits on the bottom of leaves up to 80% under certain conditions. However, the amounts were relatively low and the influence of these increases on control of whitefly in cotton and cantaloupe was not established because of low insect infestations.