Influence of Air Shear and Adjuvants on Spray Atomization

Droplet size is critical in maximizing pesticide efficacy and mitigating off-target movement. The correct selection and adjustment of nozzles and application equipment, as well as the use of adjuvants, can aid in this process. However, in aerial applications air shear tends to be the dominant factor influencing spray droplet size. The objective of this work was to take a step-wise approach to examine the influence of both adjuvant type and airspeed on droplet size in the presence of a formulated glyphosate product. Although the results show that the spray adjuvants tested did play a role in determining droplet size, as airspeed increased the differences between droplet sizes resulting from the use of the adjuvants tested decreased. A number of the adjuvant–nozzle–airspeed combinations tested did not necessarily increase droplet size or reduce fines, but this does not indicate that they do not have a place in aerial application. Other benefits that could not be measured as part of this study, such as retention and reduced evaporation, can also be critical to an application's success. For any pesticide application, applicators should read and follow product label instructions while being cognizant that the decisions they make, whether they are about nozzle selection or products, will affect droplet size.