Comparison of within canopy deposition for a solid set canopy delivery system (SSCDS) and an axial–fan airblast sprayer in a vineyard

Abstract

Solid set canopy delivery systems (SSCDS) are novel ways of pesticide spray applications in modern high–density orchards and vineyards. Through our prior efforts, SSCDS variants have been tested and adjusted to provide optimal system configurations for spray application in high–density apple orchards and vineyards. This present study compared two prior optimized variants of an SSCDS comprising treatments with 1–tier and 2–tier of emitters/nozzles and an axial–fan airblast sprayer for spray performance in a modified vertical shoot position (VSP) vineyard. Such vineyards have the vine canes constricted under trellis wires, with the top of canes being loose and more sprawling. SSCDS 1–tier had a pair of full–circle emitters installed per vine at 76 cm above the cordon. For SSCDS 2–tier, two hollow–cone nozzles were installed per vine near the drip line at 45 cm above ground level in combination with additional emitters as in 1–tier. The sprayate was a fluorescent tracer dissolved in water at 500 ppm. Spray deposition and coverage were quantified in different canopy zones and on either side of leaf surfaces using mylar cards and water sensitive papers (WSPs) as samplers, respectively. The samplers were respectively analyzed using fluorometry and image processing techniques. Analysis of deposition data indicated statistically similar mean deposition for different treatments, however, uniformity of distribution was higher for the airblast sprayer treatment. Similar and uniform deposition on the mylar cards on the adaxial and abaxial leaf surfaces was observed in all the treatments, indicating that emitters/nozzles placed within a canopy can deposit similar amounts of active ingredient as an airblast sprayer. Contrary to the deposition data, spray coverage was highest for the airblast sprayer (33.5 ± 2.8%) followed by SSCDS 1–tier (21.5 ± 2.9%) and 2–tier (19.9 ± 3.0%). Such differences could be because of the use of air-assist which was absent in SSCDS based application. In summary, SSCDS provided higher canopy deposition, however, the airblast sprayer provided higher spray coverage and better spray application uniformity. Prior biological efficacy studies in apple orchards have reported equivalent insect-pest control for SSCDS and airblast sprayer, notwithstanding the uniformity and heterogenous spray coverage. Therefore, future studies are warranted to collect season long pest management data in economically viable plot sizes in a vineyard.