The effect of adjuvants in reducing potential spray drift

Drift containment during plant protection products spray application is essential to achieve sustainable crop protection. Adjuvants are designed to perform specific functions during the mixing and application of pesticides, but they can also reduce evaporation, foaming, volatilization, and spray drift. Laboratory trials aimed to measure the capability of different adjuvants to reduce potential spray drift were performed. Two adjuvant formulations were tested separately at two dosages. Three types of nozzles were considered: conventional hollow-cone and flat fan, and air-inclusion flat fan nozzles. The effect of adjuvants on the obtained droplet size spectra were measured using a laser diffraction system. Furthermore, adjuvants effect on potential spray drift was evaluated measuring the distortion of single nozzles spray patterns, using an ad hoc designed “wind-tunnel horizontal patternator”. Pure water was used as a spray liquid reference for the evaluation of (i) changes in droplet size spectra and (ii) the potential spray drift reduction attributable to the adjuvants. Both tested adjuvants increased the droplet size spectra of the three types of tested nozzles to a different extent, in the range of 2–60% for the Volume Median Diameter. The variation of droplet size spectra was reflected in the reduction of potential spray drift, which ranged between 9 and 62%. Different reductions were observed according to the nozzle types. Significant differences between the two tested adjuvants were detected for their capability to reduce potential spray drift. Finally, the adjuvants dosage generally did not affect either the droplet size or the drift reduction figures.