Techniques for Enhancing Pesticide Distribution and Coverage during Orchard and Vineyard Spraying for Optimum Results
In the world of agricultural pesticide application, precision is key, especially when it comes to air-assisted spraying in orchards and vineyards. Operators of these sprayers use nozzles that produce smaller droplets compared to those used in field crop sprayers, a detail that significantly impacts the efficiency of the application.
Adequate spray coverage, also known as the percentage of the target covered with pesticide, is another crucial aspect. For most spray applications, a coverage of 25% to 35%, or 450 to 600 droplet stains per square inch of the card, is considered adequate.
The amount of pesticide sprayed on the target is just one piece of the efficiency puzzle. To ensure optimal results, it's essential to consider the manner in which the air is discharged from the fan. A practical method to determine the correct trajectory is to tie ribbons around the area where air exits the fan. Too little or too much air results in ineffective and inefficient coverage of the target.
Companies like TeeJet, Hardi, and Amazone offer specialized equipment in Germany designed to reduce spray drift during pesticide application in orchards and vineyards. When air cannot penetrate the canopy, it moves upward in a vertical trajectory, further exacerbating the off-target movement of droplets.
To assess the spray coverage, water-sensitive papers can be used. These papers, staked in front of, in the middle of, and behind the row, can help determine how much spray is intercepted by the canopy or passes through to the next row. Water-sensitive papers should also be affixed to the upperside and underside of leaves to provide a more accurate representation of the location and uniformity of pesticide application.
The goal in spraying fungicides and insecticides is to land as many droplets on the target as possible. To achieve this, the sprayer fan air-flow rate and volume should be adjusted so that the air being directed into the canopy replaces the air already in the canopy, but dies down significantly as it reaches the other side of the canopy. The angle of the deflectors should be adjusted according to the direction the air blows the ribbons.
It is important to take the time to adjust the air stream characteristics (direction, air speed, and air flow rate) suitable for the tree or vine canopy conditions at the time of the spray applications. Under fully-developed canopy conditions, too much air flow can force leaves together, creating a surface that blocks the passage of air.
In light of the high drift risk associated with extremely fine or fine droplets, it's advisable to avoid their use. Ribbons tied around the fan show the direction that air is exiting the sprayer, providing valuable insights for adjustments. As the nozzle's droplet size increases, the spray coverage decreases.
The angle of deflector plates on the sprayer should be adjusted to match the height of the canopy each time spraying is done at an orchard or vineyard. Water-sensitive papers placed on a rod some distance from the edge of the vineyard or orchard can be used to determine if drift is taking place.
After spraying pesticides, the coverage on these cards should be checked. The spray droplets intercepted by the water-sensitive cards leave a blue stain on normally yellow cards, representing the spray deposit and coverage. With these practices in place, farmers can ensure a more effective, efficient, and environmentally friendly pesticide application process.
