Pesticide Application in Vineyards
Minimizing Spray Drift in Vineyards
Drift usually occurs during or immediately after an application; however, it can also occur hours or days later. Pesticide spray drift is the aerial movement and unintentional deposit of pesticide outside the target area. Aside from being illegal, there are several compelling reasons to avoid it. Drift can be measured in terms of financial loss associated with wasted pesticides, wasted time, and reduced crop quality/quantity. Additionally, if an application is unsuccessful, the operator may need to reapply, incurring further costs. Pesticide drift increases the risk of damage to human health, susceptible plants (e.g., adjacent crops), non-target organisms (e.g., wild and domestic animals, pollinating insects, etc.), the environment, and property. Pesticide drift can occur as a droplet, vapor, or with soil particulates. Physical drift is the initial off-target movement of pesticide droplets.
Weather Conditions
The prevailing weather conditions at the time of spraying greatly influence spray droplet spread and capture. Weather conditions that influence the application of agricultural chemicals are discussed below.
Horizontal Wind Speed and Direction
It is important for a grower to know the wind speed and direction above the vines or target area before carrying out any spray operation.
Temperature and Relative Humidity
Water is the main material used to dilute agricultural chemicals. As it evaporates, extreme care must be taken when applying small droplets.
Surface Temperature Inversions
Avoid ground and aerial applications into a surface temperature inversion. Drift potential is high during a surface temperature inversion in the vineyard.
Equipment Modifications
Sprayer Design
Several technological advancements in spray systems are available in controlling spray drift. The most popular and least costly to the industry has been in the design of spray nozzles (e.g., air induction).
Airblast Sprayers with Deflector Plates
Carefully direct the air from the fan towards the canopy to ensure that the canopy intercepts the sprayed droplets. With conventional airblast sprayers, deflector plates must be installed on both the top and bottom of the fan, as well as on both sides of the sprayer, to guide the spray plume toward the canopy and at a level equal to the canopy’s height. The size of the deflectors should be large enough to direct the air effectively at the canopy.
Nozzle Selection
Different nozzles produce different spray characteristics. Cone nozzles produce more fine droplets than fan nozzles.
Spray Pressure
Spray pressure influences the size of droplets where by increasing the pressure results in smaller droplets.
Nozzle Spray Angle
Spray angle is the interior angle formed between the outer edges of the spray pattern from a single nozzle.
Distance between the Nozzle and Target
The less distance between the nozzle and the target means less distance for a droplet to travel thus minimizing spray drift.
Travel Speed
The travel speed of the sprayer also influences spray drift. Even when adjustments are made to restrict air intake into the fan, excessive air may still reach the canopy if the travel speed is extremely low. Slow travel speeds allow the canopy to be exposed to airflow for a much longer time period, thus contributing to drift. This situation is further exacerbated when the air speed from the fan is high, and the sprayer travel speed is low.
Drift Reducing Adjuvants
Use drift-reducing adjuvants in the spray tank as directed on the label. Most of these agents work by increasing droplet size since larger droplets are less prone to drift
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