Effect of droplet size and leaf surface on retention of 2,4-D formulations

Spray droplet wetted area and evaporation time may determine the degree of interaction between herbicides and weeds and help the understanding of their final mode of action. Ideal characteristics may be defined as resulting in minimum interaction between herbicide droplets and crops and maximum interaction between herbicide and weeds. The aim of the present study was to determine the evaporation time and wetted area of two different 2,4-D formulations, with or without glyphosate and adjuvant addition, applied at different droplet sizes to leaf surfaces of Commelina benghalensis L. and Conyza bonariensis L. The evaporation time and wetted leaf area of two different size spray droplets containing 2,4-D formulations with or without glyphosate and adjuvants and applied to adaxial leaf surfaces of C. benghalensis and C. bonariensis were quantified. The treatments consisted of four droplet sizes (500, 650, 800 and 950 mu m diameter), five spray liquids (2,4-D amine salt or 2,4-D choline salt, with or without glyphosate and adjuvant). The droplet wetted area and evaporation time were quantified through sequential image analysis under controlled environmental conditions. Droplet size, leaf surface, and type of 2,4-D formulations significantly influenced droplet retention. The results indicate 800 and 950 mu m droplet, classified as ultra-coarse, significantly increase the herbicides retention on leaf surface of Commelina benghalensis and Conyza bonariensis which is highly recommended for drift reduction, nevertheless the droplet retention strongly depend of leaf type surface and physical and chemical characteristics of spray solution.