Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 29, 2001
Publication Date: N/A
Technical Abstract: There is more risk of off-site contamination when treating tall canopies such as trees, vines and bushes because, in many cases, pest and crop management sprays must be directed up into the air. In these production systems, it is not practical or possible to deliver material downward like field crop applications. These experiments were designed to evaluate the fate of spray produced by large droplet, drift-reduction nozzles on conventional airblast spray equipment. Tests were conducted using the TD02, air inclusion nozzle and D3-25 and D4-25 conventional, disc-core nozzles. Each treatment was designed to deliver the same rate of fluorescent tracers to a row of semi-dwarf apple trees. The D3-25 nozzle treatment produced the highest droplet density and coverage on upperside and underside surfaces of apple leaves. The TD02 nozzle produced the lowest droplet density and coverage on underside leaf surfaces. Spray recovery measurements showed little difference between the canopy spray deposits produced by the TD02 and D4-25 nozzles. The air inclusion nozzle reduced off-target spray losses. The TD02 nozzle treatment produced lower sedimentation losses from 4 to 128 m downwind. The tree canopy proved to be an effective filter as both nozzle types produced higher airborne losses just above the tree canopy than within the top of the canopy. The D4-25 treatment produced higher airborne losses on high volume, air sampler filters out to 64 m downwind. The two nozzle types produced similar airborne and ground losses beyond 64 m downwind. Air inclusion nozzles may provide producers with a relatively low cost means of reducing drift losses but further research is needed to evaluate the impact of their use on biological efficacy.