Effects of surfactants and the kinetic energy of monodroplets on the deposit structure of glyphosate at the micro‐scale and their relevance to herbicide bio‐efficacy on selected weed species

Abstract

Summary The deposit pattern of foliar‐applied agrochemicals, and its relation to their bio‐efficacy, has major practical importance. Thus, in our experiments, we evaluated the relevance of the deposition properties of glyphosate for its bio‐efficacy. The deposition pattern of glyphosate monodroplets was influenced by using surfactant and by applying the droplets with or without kinetic energy to the plant foliage. Monodroplets (1 μL) of glyphosate, formulated with or without ethoxylated rapeseed oil surfactant (RSO) having on average 5, 10, 30 or 60 ethylene oxide units (EO), as well as one commercial glyphosate product (CGP), were applied either by carefully placing the droplet on the foliage with a pipette (kinetic energy assumed to be near zero) or by a monodroplet generator (with kinetic energy). We selected two easy‐to‐wet (Stellaria media and Viola arvensis) and two difficult‐to‐wet (Chenopodium album and Setaria viridis) weed species as target plants. The deposit structure was determined using a scanning electron microscope with energy dispersive x‐ray microanalysis. The kinetic energy of the droplet had no consistent effect on the deposit structure or the bio‐efficacy of glyphosate formulations. In contrast, surfactants differing in EO unit, affected both the deposit structure and the bio‐efficacy of the formulations, depending upon the species. In easy‐to‐wet species, the increase in EO unit of RSO surfactant failed to affect the deposit area of glyphosate and its bio‐efficacy. However, in difficult‐to‐wet species, the increase in EO unit of RSO surfactant reduced the deposit area of glyphosate and enhanced its bio‐efficacy.

Evaporation of pinned droplets containing polymer – an examination of the important groups controlling final shape

“…The aim of this article was to suggest means by which this ring shape could be eliminated or at least reduced. It has previously been shown that the coffee‐ring formation can be suppressed by introducing surfactant driven Marangoni flow, altering DLVO interactions, using electrowetting, changing particle shape or through careful selection of an electric field . However, none of these are ideal for P‐OLED applications.…”

“…There are a vast number of systems for which evaporation of a droplet, containing a nonvolatile component is relevant. The distribution of pesticide on leaves is important when attempting to kill weeds . There are several biological applications, for example DNA microarrays, blood residue analysis for disease diagnostics and crime scene reconstruction .…”

“…One can either try to prevent the droplet pinning or suppress the capillary flow. Adding a surfactant can introduce a Marangoni flow which counteracts the outward capillary flow. Altering the pH can influence the DLVO interactions and introduce an attraction between the nonvolatile component and the substrate, which dominates the capillary flow.…”

The impact of trough geometry on film shape. A theoretical study of droplets containing polymer, for P-OLED display applications

“…Methods which have been shown to at least reduce the extent of coffee-ring formation are in abundance. A surfactant can be introduced to initiate a Marangoni flow that counteracts the capillary flow [8,19]. An electric field can be chosen to tailor film shape, as shown by Wray et al [20].…”

“…This is due to the array of industrial and practical applications for which drying is an important step. There are several applications for biological fluids [1], including pattern analysis of dried blood, for crime scene investigation [2] and disease diagnostics [3], DNA microarrays [4][5][6][7] and herbicides/pesticides on leaves [8]. In addition, micro/nano electronics can be manufactured [9][10][11][12][13][14] diode displays (P-OLEDs) [15].…”