The Benefits Of Drift Control
Growers, applicators, managers, and pest control advisers must work together to ensure that spray drift is managed so that there is a reasonable certainty of no off-site drift. Spray equipment should be properly set up, calibrated, and maintained to maximize efficient targeting of the crop. In addition, growers should establish a spray safety program that ensures that best management practices (BMPs) for sprayer operations are followed before and during a spray application. Keep careful records of your drift control program.
The following is a checklist of sprayer best management practices:
● Know the label requirements of the material(s) planned for use.
● Practice integrated pest management. Monitor pests so spraying — when needed — is done when drift or runoff risk is low.
● Watch the weather. Avoid spraying when winds are above 10 mph (too windy) or below 3 mph (higher inversion risk) or just before a significant rain eventor irrigation (higher risk of runoff).
● Know your neighbors. Identify sensitive areas such as roads, homes, adjacent crop fields, open water, etc. that could be harmed by drift. Avoid spraying at certain times or change spray practices to protect sensitive areas. These practices might include spraying near a road very early in the morning with the help of a spotter, spraying into the outside one or two rows of an orchard that is adjacent to a sensitive area, spraying next to a sensitive area when the wind is blowing away from that location, or using a low pressure hand gun application adjacent to the sensitive area.
● Target the tree. Equipment should be set up for the most efficient application possible. This includes using sensor-guided orchard and weed sprayers (Smart Sprayers, etc.), placing properly sized nozzles in the correct positions on the spray boom, and adjusting air flow to match the air delivery to the target.
● Avoid spraying when temperatures are high and humidity is low. Low humidity and high temperatures result in rapid water evaporation and increasingly smaller droplet sizes as the spray moves away from the sprayer. Drift risk increases with decreasing humidity and rising temperatures.
● Turn off sprayer when exiting any spray row. If the applicator shuts off the sprayer outside the tree row regardless of the location on the farm, the practice will more likely be followed when it is most necessary. “If you always do it, you’ll always do it.”
● Lower spray pressure — within the nozzle manufacturer’s recommended pressure range — can reduce the number of small droplets produced by conventional nozzles without reducing efficacy. High spray pressures increase the risk of equipment failure (hoses, seals, etc.). Follow sprayer manufacturer’s recommendations for sprayer pressure.
● Pesticide selection can be a key part of drift management. Certain pesticides are more prone to drift via volatilization — that is, they move as a gas — such as 2,4-D. Using a lower toxicity pesticide, even if it costs more, when spraying close to sensitive areas will help reduce harm from any potential drift. Use a pesticide registered for the crop in the next field whenever possible, so if drift occurs there is not an illegal residue on that crop.
● Drift control adjuvants can increase droplet size and may reduce spray drift. There are many different drift control adjuvants in the market.
● Reduce the distance from the nozzle to the target. The shorter the distance the droplet has to travel, the less chance for loss from wind, evaporation, etc. Lower the spray boom on herbicide sprayers or use a tower on orchard air blast sprayers to get the nozzle(s) closer to the target.
● Protective shields on herbicide sprayers help reduce movement of fine droplets off target.
● Use the largest spray droplets whenever possible. Droplet size is the single most manageable factor that affects spray drift (see table), but specific information on how to use droplet size to manage drift in orchards is limited. Select nozzles that deliver the largest droplets possible without compromising spray efficacy. Larger droplets may not provide the same degree of spray coverage quality as smaller droplets, so a compromise between coverage and droplet size may have to be made. Systemic pesticides (glyphosate, etc.) often work well when applied using large droplets, but pesticides requiring full coverage may require smaller droplet sizes to deliver effective control.