S14 - Session P5 - Characterizing spray deposition for control of trunk pests from an experimental airblast sprayer with 5-port nozzle bodies

Authors: Lauren Fessler, Wesley Wright, Grace Piestch, Liesel Schneider, Heping Zhu, Cody Fust, Amy Fulcher, University of Tennessee, 112 Plant Biotechnology Building, 2505 E.J. Chapman Drive, Knoxville, TN 37996-4500, United States of America; afulcher@utk.edu (presenting author)

In order to control trunk borers with contact insecticides, thorough coverage is presumed necessary. While not designed for truck applications, nursery operators commonly use airblast sprayers for this purpose due to their high labor efficiency and perceived ability to adequately spray trunk and canopy pests simultaneously. This study quantified spray deposition on red maple trunks in a 3-row block from two application rates, 1380 and 1070 L⸱ha -1 , from a vineyard airblast sprayer equipped with laboratory-designed 5-port nozzle bodies (Zenit B11, Hardi Intl.). Water sensitive wraps placed at four heights (11.4 to 77.5 cm) on trunks in each row were analyzed for coverage after spraying the block from both sides with all 20 nozzles on the proximal side of the sprayer. Wind ranged from 1.0 to 1.8 m⸱s -1 for the 1380 L⸱ha -1 application and was 0 m⸱s -1 for the 1070 L⸱ha -1 application. While there was a row × direction × height interaction ( P = 0.0304), within each row, portions of wraps facing the same direction did not differ in coverage regardless of height. On the interior row only, coverage was greater at 1070 L⸱ha -1 than at 1380 L⸱ha -1 ( P < 0.0001), possibly due to reduced wind allowing greater penetration into the interior row. For both rates, while the face of the trunk proximal to the sprayer in the exterior rows had high coverage, ranging from 77-95%, the opposite side averaged just 38% coverage, resulting in a total coverage of only 53% on average. High coverage is possible for a wide range of trunk heights on the proximal face of exterior rows; however, for a 3-row block of trees, applications of 1380 L⸱ha -1 or less from this specialized sprayer may not achieve 100% coverage around the entire trunk. Further optimization to nozzle height, number of rows, and spray rate should be explored.