Submitted to: Entomological Society of America Regional Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/23/2004
Publication Date: 2/26/2004
Citation: Kirk, I.W. 2004. Tank-mix adjuvants, droplet size, and spray drift. In: Proceedings of the Southwestern Branch of the Entomological Society of America Meeting, February 23-26, 2004, Lubbock, Texas. p. 29-30.
Interpretive Summary: Drift of agricultural sprays from fields where they are applied onto adjacent sensitive crops or environmentally protected sites is a serious problem for spray applicators. Regulatory agencies are now specifying sprayer settings and/or operational conditions such as spray droplet size for application of products that may be prone to drift and cause off-target damage. Applicators can reduce incidents of spray drift and associated off-target damage by judicious selection of spray nozzles and application conditions to increase spray droplet size and reduce the driftable fine droplet component of the spray. Spray nozzle atomization data and models are available to aid applicators in selection of application conditions. Use of drift control additives in the spray mix is an additional tool that applicators can use to reduce spray drift. However, information on the quantitative effectiveness of different drift control additives is not readily available to applicators since there are no labeling or efficacy requirements for these products. A spray droplet size study was conducted in a wind tunnel with twelve drift control additives in a simulated spray mix. Most of the drift control additives increased spray droplet size and reduced the amount of fine spray droplets that are prone to drift from the application site. Applicators can use the information developed in the study to control spray drift by selecting and using effective drift control additives.
Technical Abstract: Drift of agricultural sprays is important to aerial applicators because of potential damage to off-target sites and possible associated litigation. Spray mix adjuvants are marketed for reducing spray drift. The primary effect of these adjuvants is increasing spray droplet size and reducing the driftable fine component of the spray spectrum, which are the primary factors influencing spray drift. Simulated agricultural sprays were atomized in a wind tunnel with drift reduction adjuvants in the spray mix at rates and conditions typical of aerial spray application. The effectiveness of the adjuvants in increasing spray droplet size is different for different adjuvants. Based on these wind tunnel studies with the EC blank spray mix, the drift retardant adjuvants in this study - except for three that were ineffective in the EC blank spray mix - should provide a measure of spray drift mitigation in commercial use. The measure of drift mitigation attained with drift reduction adjuvants is a matter that applicators can balance or optimize based on adjuvant performance and economics to achieve drift mitigation goals for a given application.