Autores:

Ulisses R. Antuniassi,1 Alisson A. B. Mota,2
Rodolfo G. Chechetto,2 Fernando K. Carvalho,2
Marcio L. M. Santos,2 Ramiro F. L. Ovejero,3
Henrique N. Barbosa,3 and Matheus G. Palhano3

This study evaluated the impact of spray solution recirculation caused by pumping and pressure on the droplet spectra generated when spraying dicamba and glyphosate solutions, with different drift-reducing adjuvants (DRAs) and using the test protocol developed for the approval of DRAs for dicamba. A total of 13 adjuvants (including products based on polymers, surfactants, and oils) were tank-mixed with a 100 L/ha solution that contained XtendCam (dicamba diglycolamine salt, 480 g/L at 1.0 L/ha) and Roundup Transorb R (glyphosate potassium salt, 588 g/L at 2.0 L/ha).

A sprayer equipped with a piston pump was used to simulate the pumping recirculation process, providing pressure of 3 and 5 bar to a Teejet TTI 11003 nozzle inside a spray chamber, where the droplet spectra generated over time were analyzed by a Sympatec Helos laser diffraction particle analyzer. Four recirculation levels were considered: 0, 4, 10, and 16 cycles (one cycle means one pass through the pump). The volume median diameter (VMD) and the percentage by volume composed of droplets smaller than 150 µm (V150) were used as parameters to analyze the adjuvants’ performance.

The results showed that pumping at 5 bar was a worst-case scenario for all DRAs. The increase in VMD after applying recirculation showed that some DRAs need high shearing to achieve their best performance; thus the compressed air sprayers used in experimental stations and laboratories may not be suitable for this type of research. There were more DRAs that gave larger droplets (higher VMD value) than DRAs that reduced the number of fines in the spectrum, since only 2 out of 13 DRAs managed to meet the approval criteria regarding V150, while 7 out of 13 managed to meet the criterion in terms of VMD.

U. R. Antuniassi, A. A. B. Mota, R. G. Chechetto, F. K. Carvalho, M. L. M. Santos, R. F. L. Ovejero, H. N. Barbosa, and M. G. Palhano, “Interference of Spray Solution Recirculation and Pressure on the Performance of Drift Reducing Adjuvants for Dicamba Plus Glyphosate Applications,” in Pesticide Formulation and Delivery Systems: 43rd Volume, Creating Certainty in an Uncertain World, ed. Danny Brown (West Conshohocken, PA: ASTM International, 2025), 79–95, http://doi.org/10.1520/STP1652202400144