Spray Delivery to Nursery Trees by Air Curtain and Axial Fan Orchard Sprayers

Abstract

Two types of air-assist sprayers were used to treat, from one side only, a single row of hedge-pruned, red maple ( Acer rubrum L. ‘Red Sunset’) trees in a commercial Ohio nursery. A traditional orchard type sprayer and a prototype air curtain sprayer using crossflow fans and hydraulic nozzles were evaluated for differences in canopy deposits, spray coverage, and downwind ground deposits. The air curtain sprayer produced more uniform deposits vertically but not higher mean deposits than the traditional orchard type sprayer. The air curtain sprayer also produced somewhat higher ground deposits downwind of the treatment area. There were no differences in spray coverage between sprayers despite differences in the droplet spectrum produced by each sprayer. Evidence from the coverage and ground target samples indicate that slower fans on the air curtain sprayer might be needed to reduce air speed to retain more spray within the tree canopy. As operated, neither of the sprayers can be expected to produce uniform spray deposits around the nursery stock if treatments are made from one side of the row only. Canopy and ground target deposits indicate that alternate row spraying will not necessarily produce uniform deposits across two tree rows as planted at the test site.