Spray coverage in apple and cherry orchards using a solid set canopy delivery system

S.M. Niemann, M.D. Whiting
A multidisciplinary team is refining a solid set canopy delivery system (SSCDS) as a permanent, multi-plane system for applying agrochemicals in tree fruit orchards. This paper reports on product distribution and canopy coverage, comparing the SSCDS with standard airblast application technology. Coverage trials were conducted in planar sweet cherry and apple orchards with assessments made approximately every four weeks between full bloom and full canopy to determine how canopy development impacts coverage. Each application was made at 935 L ha-1. Water and oil sensitive spray cards (2.54×2.54 cm) were attached in pairs mimicking abaxial and adaxial leaf surfaces to trellis wires using Velcro®. In the apple orchard, cards were placed at three heights, 2.4 1.8, and 1.0 m. In the cherry orchard, cards were placed at 2.1, 1.5, and 0.9 m. Coverage trials in apple and cherry coincided with commercial applications of chemical thinners and one GA3 treatment in cherries, subsequent applications consisted of only water. After each application, coverage cards were collected once they dried completely. Percent coverage and droplet size were analysed using DepositScan software provided by the USDA Agricultural Research Service. The airblast sprayer provided more uniform distribution throughout the season and therefore better coverage (57% card surface area) compared to SSCDS (19% card surface area) and greater product deposition 39.9 and 8.7 uL cm-2 respectively. These trials also revealed deficiencies in the SSCDS, particularly for treating the abaxial portions of leaves. Continued engineering of nozzle type and placement in the SSCDS is warranted.
Niemann, S.M. and Whiting, M.D. (2016). Spray coverage in apple and cherry orchards using a solid set canopy delivery system. Acta Hortic. 1130, 647-654
DOI: 10.17660/ActaHortic.2016.1130.96
water and oil sensitive spray cards, trellised canopies, airblast sprayers

Acta Horticulturae