Optimization of Herbicide Use: Study on Spreading and Evaporation Characteristics of Glyphosate-Organic Silicone Mixture Droplets on Weed Leaves

Abstract

Herbicide deposition rate can be affected by the leaf surface features of weeds and have a significant impact on the overall efficacy. In this paper, an orthogonal experiment was conducted to investigate the differences of droplet evaporation and spreading characteristics corresponding to weed leaf surface with hairy, waxy and rough (ridged) structures. Three weed species—Descurainia sophia, Lepidium lotifolium, and Lolium temulentum—were included in the study, representing these three leaf structures respectively. Glyphosate sprays with organic silicone surfactant in different concentrations were composed for the test. Single droplets with two diameters of 0.05 μL and 0.1 μL were deposited on the leaves to evaluate the evaporation and spreading characteristics. A digital camera was used and the evaporation duration and the maximum droplet coverage images could be captured and extracted from the recorded videos. The Image Processing Toolbox in Matlab was applied to segment the images for droplet and leaf background and the binary images’ pixel numbers were counted for coverage area calculation. The results revealed that the evaporation duration was reduced with the increase of the organic silicone concentration, while the spread area was expanded. The droplet spread more widely and evaporated faster on D. sophia leaves than on the leaves with L. lotifolium and L. temulentum surfaces. The spreading area and evaporation duration varied much faster on L. lotifolium leaves than on the leaves of other weed species. The droplet sizes affected spreading more significantly on L. temulentum leaf surface, as the spreading procedure of small size droplets was restrained by the groove structure. The results of this study would benefit the consideration of the farmers when selecting the proper nozzle code and the determining of the surfactant mixture in order to optimize the use of herbicides like glyphosate.

Effect of Adjuvant on Glyphosate Effectiveness, Retention, Absorption and Translocation in Lolium rigidum and Conyza canadensis

“…The need for the addition of adjuvants to glyphosate solutions was previously reported by Castro et al [1], who claimed that glyphosate alone or in its different salt forms could not effectively penetrate specific structural elements of plant surfaces. This was also supported by Li et al [6], who reported that an added surfactant leads to improved droplet coverage on leaves and therefore to better absorption of glyphosate.…”

“…The absorption process requires thorough research around the various parameters that affect retention, spreading, penetration, and finally the translocation of pesticide substances within the plant tissues. Therefore, some of the important parameters that should be taken into account are the specific characteristics of the plant surface (i.e., wax composition and leaf roughness) and the traits of the sprayed liquid [6]. Regarding the leaf surface characteristics that affect spray adhesion, the trichomes, the cuticular membrane and the extent of wax act as interceptors to droplet spreading [22].…”

Effect of Adjuvants and pH Adjuster on the Efficacy of Sulcotrione Herbicide

“…Other studies have shown that the use of an organosilicone surfactant can contribute to a significant increase in the coverage of barnyardgrass leaves by liquid drops [33]. However, it should be remembered that an increase in leaf wetting may lead to an increase in the evaporation rate of spray liquid drops [34]. Adjuvants are substances that do not have a direct herbicidal effect, but they can modify the properties of the spraying liquid, which can lead to an increase in the effectiveness of herbicides [35].…”

Can Control of Glyphosate Susceptible and Resistant Conyza sumatrensis Populations Be Dependent on the Herbicide Formulation or Adjuvants?

“…Herbicide efficacy can be significantly enhanced by the addition of adjuvants, leading to increased uptake and translocation of the active ingredient [9]. In relation to targeting efficiency, the addition of adjuvants either in the formulated products or in the tank mixtures has been reported to improve glyphosate absorption and translocation in the plant tissues [1,10].…”