Pesticide Application in Vineyards
The pesticides used to control weeds, insects, and diseases in the vineyard are applied with sprayers, which can either be tractor-mounted, pull-type, pickup-mounted, and self-propelled. All sprayers have several basic components: tank, pumps, filtration devices, fans, and nozzles.
Tanks should be made of a corrosion-resistant material. Suitable materials used in sprayer tanks include stainless steel, polyethylene plastic, and fiberglass because of their rust and corrosion resistance. Stainless steel tanks are the most durable, corrosion-resistant, and the strongest option. Due to their high cost, they make the most sense for high-use spraying situations.
Many spray mixtures must be agitated (stirred up) to keep the pesticide and carrier mixed. For liquid concentrates, soluble powders, and emulsions, the system bypass line is usually adequate to keep the formulation well mixed.
Direct Injection Sprayers
Direct injection sprayers use separate tanks for the water and the pesticide. The pesticide is injected into the water stream at a rate dictated by the forward speed and controller. While more costly to purchase, injection sprayers have the advantage of reducing risk since you never mix more than needed.
The pump must deliver the necessary flow to all nozzles at the desired pressure to ensure uniform distribution. When selecting a pump, consider the pressure ranges the pump can handle, the gallons per minute it can supply, its resistance to corrosive damage from pesticides, ease of priming, and power source availability. It’s a good idea to choose a slightly oversized pump. A pump must have sufficient capacity to operate a hydraulic agitation system, as well as supply the necessary volume to the nozzles.
Piston pumps are among those most commonly used for applying agricultural chemicals. These are positive displacement pumps that can be used for both corrosive and abrasive materials. There are two types of piston pumps used for different application purposes: high pressure-low volume-high speed, and low pressure-high volume-low speed applications.
Diaphragm pumps, although often more expensive than other pumps but have some important advantages in use and maintenance.
Centrifugal pumps are the most popular type for low-pressure high-volume sprayers. They are durable, simply constructed, and can readily handle wettable powders and abrasive materials. Pumping action is created by a high-speed impeller that literally throws the materials out of the pump.
Roller pumps are widely used on low-pressure boom sprayers for herbicide application and run efficiently at low power take-off (PTO) speeds.
Proper filtering of the spray mixture not only protects the working parts of the spray system but also avoids misapplication due to nozzle tip clogging. Three types of strainers commonly used on sprayers are tank filler strainers, line strainers, and nozzle strainers. As the mixture moves through the system, strainer openings should be progressively smaller. The large mesh at the tank opening prevents large contaminants (grass, rocks, labels, etc) from entering the tank upon filling.
Fans are used to move spray into vines to enhance the uniformity of pesticide deposition on berries, foliage, and wood. Air movement also displaces leaves and branches, which aids spray penetration and increases the exposure of surfaces to spray.
The nozzle regulates the flow rate, atomizes (breaks up) the mixture into droplets, and disperses the droplets in a specific pattern. Nozzle type and location also influence spray pattern. Nozzles usually have several components, including a body, cap, strainer, disc and core (orifice and whirl plate).
Other System Components
A pressure regulator is one of the most important parts of a sprayer. It controls the pressure and therefore the quantity of spray material delivered by the nozzles.
Pressure gauges monitors spray system operations because a sprayer is set up to operate within a specified pressure range.
Control valves should be located between the pressure regulator and the nozzles in order to regulate the flow to specific boom or manifold sections or even to individual nozzles.
New systems using electronics have been developed to improve pesticide application. These systems can monitor and guide the spray equipment in various ways.
Hoses, Clamps, and Fittings
All components that come in contact with the chemical mixtures should be constructed of materials that are resistant to chemicals and to sunlight degradation.
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