Submitted to: Pesticide Drift Educator's Conference
Publication Type: Proceedings
Publication Acceptance Date: May 18, 2001
Publication Date: N/A
Interpretive Summary: Airblast sprayers pose a greater risk of spray drift than most other ground-based application methods because they deliver spray horizontally and vertically towards a target area. Several factors, including weather conditions, crop canopy, and sprayer setup can significantly influence the amount of spray drift. The most significant factor in determining the risk kof spray drift is spray droplet size. Smaller droplets improve coverage and may provide better pest control but they are also more likely to be blown through, around, or above a canopy. ARS and university research has shown that some air induction nozzles can be used on conventional airblast sprayers for reducing drift without significantly reducing coverage compared to conventional disc-core nozzles. ARS research has also demonstrated that tower-type of liquid and air delivery systems significantly reduce the amount of material pushed above the top of the canopy. This presentation demonstrates how these findings can be incorporated into current production practices for reducing drift and providing treatment that is more efficacious. Also illustrated are other methods for reducing spray drift including electronic technology that detects the absence of a canopy in front of the nozzles so no spray is delivered and the potential benefits of live barriers bordering treatment areas. Using these practices, operators can optimize their pest management program while minimizing their impact on non-target areas and organisms.
Technical Abstract: Airblast sprayers pose a greater risk of drift than broadcast sprayers because they deliver spray horizontally and vertically towards a target area. Weather conditions, crop canopy and sprayer setup contribute to the risks of drift from airblast sprayers. Droplet size is the most important factor in determining the potential for drift. Smaller droplets improve coverage but are more likely to be blown through or above a canopy. ARS research has shown that the coarser droplet spectrum produced by air induction nozzles can significantly reduce off-target deposits. With proper selection, air induction nozzles also can produce leaf surface spray coverage that is similar to conventional disc-core nozzles. Tower, cross-flow and wrap-around sprayers reduce drift by directing spray horizontally, which keeps the spray closer to the ground and minimizes off-target movement. Matching the air delivery system for the desired travel speed and the target canopy characteristics will help provide enough energy to move spray droplets into the canopy and limit further downwind movement. Spray delivery can be turned off when no canopy has been detected in front of different nozzle sections through use of electronic canopy sensing technology. Limiting sprayer operation to periods when there are canopies in front of nozzles significantly reduces drift. Live barriers along the boarders of a treatment area can also reduce drift as do canopies within a treatment area but they do not necessarily eliminate the risk of drift. Most importantly, equipment operators should be aware of the limits to efficient operation of their sprayers, especially when operating near sensitive areas or when other factors increase the risk of spray drift.