WITHIN-CANOPY SPRAY DISTRIBUTION FROM FIXED-WING AIRCRAFT

We have evaluated two approaches to improve spray deposition within cr op canopies from insecticide applications with fixed-wing aircraft. Bo th approaches involve increasing air velocity and turbulence in the cr op 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. T he 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 w ith boom and operational conditions modified to increase wake intensit y. Results of deposit measurements from leaf washes and water-sensitiv e paper, both on the top and bottom of leaves, at the top and midway d own in the crop canopy, show that a high percentage of spray is deposi ted on the top of leaves. The treatments with higher wake intensity in creased deposits on the bottom of leaves up to 80% under certain condi tions. However, the amounts were relatively low and the influence of t hese increases on control of whitefly in cotton and cantaloupe was not established because of low insect infestations.