Evaporation and wettability of fungicide spray, with or without adjuvant, on leaves of vegetables

ABSTRACT On tomato, cucumber and bell pepper cultivation, commonly large quantities of plant-protection products are applied, to control pests and diseases, as a way to guarantee better productivity and final product quality. The knowledge of spreading and evaporation time of spray droplets is fundamental to understand the interaction between fungicides and target surface for proper distribution of this fungicide. This study was installed to determine the wetting area and droplet evaporation of sprays containing the fungicide Cabrio Top, with or without adjuvant Nimbus®, deposited on leaves and artificial surfaces (glass slide). A system was used which analyzes images composed of a droplet generator, a stereoscope camera for capturing images and a climatic chamber for controlling temperature and relative air humidity. Droplets of 600 µm in diameter containing spray solution were deposited on leaf surfaces and on glass slide and sequential images were used to quantify the wetting area and the evaporation time. The spray solution and the target surface are determinant for wetness and droplet evaporation after deposition. Evaporation time and surface tension were inversely proportional to the wetting areas. Addition of adjuvant Nimbus® (0.5%, v/v) reduced the surface tension and provided an increase in the wetting surface area, except on tomato leaves which had shown low wetting capacity in both fungicide solutions applied.