Volume 7, Issue 7 (July 2010)
Spray Drift Reduction Technology Adjuvant Evaluation
Twelve commercial drift reduction agents were evaluated for their characteristics in the three most commonly accepted parameters for spray droplet size formation—extensional viscosity, dynamic surface tension, and kinematic viscosity. Samples were sprayed in both water and in the presence of a commercial herbicide formulation. The spray droplet spectra for these agents were then determined under rigorous control, in still-air conditions, using a Sympatec HELOS/KF laser diffraction particle size analyzer. Spraying an actual pesticide formulation that contains a wetting agent is important because the surfactant present reduces dynamic surface tension and can significantly reduce spray droplet diameter. The aerosol particle size distributions were measured using an electronic actuator that moved the nozzle spray pattern through the laser in a reproducible manner. There are multiple mechanisms that can influence both volume mean diameter and percent fines below 105 microns. There are natural and synthetic water-soluble polymers that function by increasing extensional viscosity. There are oil products that produce emulsions that keep small spray drops from forming. The droplet spectra for the different commercial products were grouped according to their specific drift reduction mechanism in order to see if a better correlation could be made on how they individually affected the resulting droplet particle size distribution.