Effect of emitter type and mounting configuration on spray coverage for solid set canopy delivery system

Timely and precise application of chemicals is critically important for improved pest control and reduced off-target movement of chemicals. A fixed or solid set canopy delivery (SSCD) system with emitters within a tree canopy has potential to reduce chemical loss and cost by applying right amount of spray at right time and location under favorable ambient conditions. The study was conducted to quantify spray coverage using various emitters mounted at different configurations within tree canopy using a SSCD system. Six different emitter (E) types with varying characteristics were selected for a field study. Each emitter was installed in four different mounting configurations. Water sensitive cards (WSCs) were mounted on upper- and under-side of leaves at 22-25 locations on each tree. After spray application, the WSCs were scanned and analyzed for percent coverage. The configuration with 80 degrees hollow cone emitters (E6) attached to a Y-connector and mounted at height of 2.0 m from the ground exhibited greater mean coverage on the WSCs placed on upper-side (58%) and under-side (21%) of leaves as compared to other emitter and configurations. It was found that coverage with this arrangement was nearly equal in upper (57.5%) and under-side (51.3%) of leaves in the high canopy region, which was the area where emitters were spraying directly. Therefore, configuration using E6 on Y-connector provided the desired uniform canopy coverage, however emitters at more locations would have to be installed to achieve similar coverage in the medium and low canopy regions. (C) 2014 Elsevier B.V. All rights reserved.