Pesticide Application in Vineyards
Canopy sprayers are used in the vineyard to control insects and diseases while herbicide sprayers are for weed control. The two are not interchangeable. The types of canopy sprayers used to apply pesticides to the grapevines typically are of three main designs: 1) vertical boom sprayers, 2) air-assisted sprayers, and 3) electrostatic sprayers.
Vertical Boom Sprayers
Vertical boom sprayers apply pesticide using a high pressure hydraulic sprayer equipped with a vertical boom for vineyard pest management. Insecticides and fungicides are often applied under high pressure because a finer spray is needed to obtain good coverage of the foliage.
Air-assisted sprayers use air as a carrier to break up the liquid into droplets using hydraulic nozzles. Both cone- and fan-type nozzles have been used in air-assisted sprayers. Wide-angle cone nozzles permit very efficient break-up of the spray, but when larger droplets are needed, a narrow cone is used.
Airblast (axial fan) Sprayers
Airblast sprayers (See Figure 26.2) use a high volume of air to dispense the pesticide nozzles (usually hollow or solid cones) that are situated radially within the air outlet of the sprayer and projected as a large radial plume of droplets towards the vine canopy.
Airblast sprayers (See Figure 26.3) can be modified with the addition of a “grape tower” mounted onto the air outlet of a centrifugal or axial fan.
Directed Air Duct Sprayers
Low volume, low velocity air is produced by a relatively small fan with separate ducts delivering the air past each nozzle (See Figure 26.4).
Multi-head Fan Sprayers
Multi-head sprayers (See Figure 26.5) utilize a number of shrouded small axial fans which can be independently adjusted to direct high volume, low velocity converging air streams to the canopy.
Tunnel (Re-circulating) Sprayers
Tunnel (re-circulating) (See Figure 26.6) sprayers straddle the vine canopy forming a three-sided “tunnel” that catches any excess spray not deposited on the vine foliage with the inside tunnel walls.
Electrostatic sprayers (See Figure 26.7) use air-shear nozzles, whereby the solution (chemical and water) is combined in a “shearing” action, which atomizes the particles down to extremely fine water droplets (< 50 µm). Then, just before the mist exits the nozzle, it is exposed to a high voltage/low current charge, usually at or near the nozzle outlet producing electrically charged (negative) spray droplets, which are carried into the vine canopy in a high speed air stream.
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