Effect of surfactant concentration on the evaporation of droplets on cotton (Gossypium hirsutum L.) leaves

Biological, surface, and wetting behavior of bio-surfactants tank-mixed with trifloxysulfuron-sodium on Sorghum halepense

BACKGROUND

There is a public interest in developing bio-surfactants due to their low toxicity and high biodegradation potential. However, their biological, surface, and behavior to use with agrochemicals has not been investigated.

RESULTS

Critical micelle concentrations (CMCs) for the synthetic surfactant dioctyl sodium sulfosuccinate (DOSS), the bio-surfactant rhamnolipid (RL), and the bio-surfactant surfactin (SF) were 1200, 50, and 50 mg L^-1 , respectively. Based on the ability of the surfactants to reduce the surface tension of trifloxysulfuron-sodium spray solution at 0.25 to 1× CMC, they are ranked SF > RL > DOSS, while at 1.5 to 4× CMC, they are ranked SF = RL > DOSS. Without surfactant, trifloxysulfuron-sodium at 10.04 g ha^-1 reduced johnsongrass growth up to 50% (ED₅₀ ). At best, SF at 1 to 4× CMC halved ED₅₀ . Unlike DOSS, which increased ED₅₀ (12.89 g ha^-1 ) due to a phytotoxic effect, SF and RL at 4× CMC decreased ED₅₀ (5.19 and 6.50 g ha^-1 , respectively) without a phytotoxic effect. A 5-μl droplet containing SF dried faster due to greater spread on the leaf surface than other surfactants. Although the wetted area of the leaf with the droplet containing RL was wider than that of DOSS, it took longer to dry. This observation contradicts the previous theory.

CONCLUSION

In terms of dosage, safety, and efficacy, the RL and SF were comparable to DOSS in other tank-mix with trifloxysulfuron-sodium. It seems that RL also works as a humectant, while SF likely works as a wax solubilisant. © 2023 Society of Chemical Industry.

Effects of tank-mix adjuvants on physicochemical properties and dosage delivery at low dilution ratios for unmanned aerial vehicle application in paddy fields

BACKGROUND

Unmanned aerial vehicles (UAVs) have been developed to improve the efficiency of pesticide applications, and they are now widely utilized in Asia. The deposition and retention periods of pesticides on plant surfaces present serious challenges for modern precision agriculture, as these factors directly affect pesticide bioavailability, efficacy, and loss. Tank-mix adjuvants have been utilized to improve pesticide performance, but their effects on physicochemical properties and dosage delivery at low dilutions are not well understood.

RESULTS

We found that different tank-mix adjuvants affected droplet impact behavior, the wetting and spreading of spray dilutions, and pesticide deposition on rice leaves by changing the physicochemical properties of spray dilutions. The adjuvant methyl oxirane polymer with oxirane, mono (3,5,5-trimethylhexyl) ether (adjuvant c) significantly reduced the dynamic surface tension of the spray dilution and inhibited the rebound of large droplets (D₀  = 2 ± 0.2 mm) and spray droplets (0.2 MPa with a LU-01 nozzle) on rice leaves, and improved the wetting and spreading performance of the spray dilution on rice leaves. Field tests showed that adjuvant c could significantly increase the deposition of chlorantraniliprole on rice leaves.

CONCLUSION

Overall, the use of appropriate tank-mix adjuvants at low dilution ratios for UAV application in paddy fields can improve the performance of spray dilutions, increase the effective deposition and wetting spread of pesticides on rice leaves, further reduce the dosage of pesticide products and improve pesticide utilization. © 2022 Society of Chemical Industry.

Fabricating Network-Link Acetamiprid-Loading Micelles Based on Dopamine-Functionalized Alginate and Alkyl Polyglucoside To Enhance Folia Deposition and Retention

The development of an eco-friendly nanopesticide formulation can alleviate the problems of low pesticide utilization and environmental pollution. However, the development of green nanopesticide carriers with ideal physical properties and specific bioavailability is still a challenging task at present. In this study, we propose a novel binary additive pesticide carrier system that is a functional polysaccharide-based polymer/surfactant (Alg-DA/APG) to improve the deposition and retention of pesticide droplets. The self-assembled micelle morphology of Alg-DA/APG and its effect on the apparent viscosity were investigated by transmission electron microscopy (TEM) and a Discovery HR-2 rotational rheometer. Surface tension was carried out to investigate the surface activity and critical micelle concentration (CMC) of Alg-DA/APG. The drop impacting experiments exhibited superior antisplash performance of Alg-DA/APG. Furthermore, a binary additive was used as the carrier material and loaded acetamiprid to prepare nanopesticide formulation Ace@Alg-DA/APG. The encapsulation efficiency (EE) and acetamiprid release behavior from Ace@Alg-DA/APG were also studied. Moreover, the dynamic contact angle (DCA) and retention experiment showed that the DCA and wetting radius at 600 s were, respectively, 6.8 ± 2.39° and 4.044 ± 0.0662 mm for the Ace@0.05 wt % Alg-DA/0.05 wt % APG on the banana foliage surface, and its retention rates on foliage surface were up to 74.80% after washing. The novel binary additive as a nanopesticide carrier has the potential to alleviate the problems of low pesticide utilization and environmental pollution in the future.

Manipulating Nano-suspension Droplet Evaporation by Particle Surface Modification

The evaporation of a nano-suspension droplet on a substrate has gained extensive attention recently due to its potential application in the rising industry of functional coating. In this paper, we reported that the droplet evaporation behavior can be controlled by the nanoparticles' concentration and the functional group on the surface of nanoparticles. Experimental results indicated that the suspension of nanoparticles notably enhanced the evaporation rate of droplets and decreased the duration time of the continuous-contact-radius (CCR) stage. This effect was more obvious when the nanoparticles were modified by the perfluorodecyltrimethoxysilane (PDTS), which made the particles more hydrophobic. Besides, the modified nanoparticles can effectively inhibit the formation of coffee rings during evaporation. These results may have important applications for the energy-efficient enhancement of the water evaporation rate.

Impact of the equilibrium relationship between deposition and wettability behavior on the high-efficiency utilization of pesticides

BACKGROUND

Often, due to the occurrence of powdery mildew, cucumber leaf surfaces is changed into a more hydrophobic surface, which affects wetting and spreading of liquid pesticides, reducing their efficiency. The wetting and deposition behavior of liquid pesticides can be improved by adding surfactants to pesticides. Added surfactants affect the spray volume of the pesticide, which can lead to waste and a low utilization rate of the pesticide. It is important to further balance the relationship between deposition and wettability of pesticide liquid on the surfaces of healthy leaves and powdery mildew leaves of cucumber.

RESULTS

This study evaluated the deposition and wettability of hexaconazole (Hexa) with surfactants on the surfaces of healthy leaves and powdery mildew leaves of cucumber. The deposition rates of Hexa with surfactants were lower than that of Hexa due to the loss of solution in conventional spray volume (750 L ha^-1 ). The deposition rate of Hexa did not necessarily increase with increasing spray volume, and the deposition rate did not increase again after the spray volume increased to a certain level. Under the condition that the prevention and control effect were not reduced, we found that the volume of solution spray with added Silwet618 or AEO-5 should be adjusted to half of the normal volume, while the volume of solution spray with added 1227 or rosin-based quarternary ammonium should be adjusted to two-thirds of the normal volume to increase the deposition rate by approximately 30%. Regarding the wetting parameters, the results showed that the wettability of Hexa with Silwet618 was the best, but their combination was not ideal according to the composite index and deposition. By analyzing all the parameters, it was found that the spray volume reduction of Hexa with surfactant was approximately equal to the solution surface tension reduction, compared with the parameters of Hexa.

CONCLUSION

The equilibrium relationship between deposition rate and wetting parameters was determined to provide guidance for the application of surfactants and to lower the dosage of pesticides to increase their efficiency and reduce their application. © 2021 Society of Chemical Industry.

Evaporating droplets on inclined plant leaves and synthetic surfaces: Experiments and mathematical models

HYPOTHESIS

Evaporation of surfactant droplets on leaves is complicated due to the complex physical and chemical properties of the leaf surfaces. However, for certain leaf surfaces for which the evaporation process appears to follow the standard constant-contact-radius or constant-contact-angle modes, it should be possible to mimic the droplet evaporation with both a well-chosen synthetic surface and a relatively simple mathematical model.

EXPERIMENTS

Surfactant droplet evaporation experiments were performed on two commercial crop species, wheat and capsicum, along with two synthetic surfaces, up to a 90° incline. The time-dependence of the droplets' contact angles, height, volume and contact radius was measured throughout the evaporation experiments. Mathematical models were developed to simulate the experiments.

FINDINGS

With one clear exception, for all combinations of surfaces, surfactant concentrations and angles, the experiments appear to follow the standard evaporation modes and are well described by the mathematical models (modified Popov and Young-Laplace-Popov). The exception is wheat with a high surfactant concentration, for which droplet evaporation appears nonstandard and deviates from the diffusion limited models, perhaps due to additional mechanisms such as the adsorption of surfactant, stomatal density or an elongated shape in the direction of the grooves in the wheat surface.

Glycine betaine-based ionic liquids and their influence on bacteria, fungi, insects and plants

Natural origin ionic liquids with betaine-based cations as new agrochemicals.

Indoxacarb-Loaded Anionic Polyurethane Blend with Sodium Alginate Improves pH Sensitivity and Ecological Security for Potential Application in Agriculture

Traditional pesticide formulations show poor utilization and environmental safety due to their low foliage adhesion and large auxiliaries. In this study, a novel and environment-friendly indoxacarb formulation was prepared to improve the pesticide's utilization rate, target control characteristics and ecological security. Indoxacarb-loaded waterborne polyurethane-sodium alginate (PU/SA) nanoemulsions with film forming properties, alkaline responsive release, high effectiveness against Spodoptera litura, and reduced acute contact toxicity for nontarget organisms were successfully prepared. The colloidal properties, swelling and release behaviors, leaf adhesion, degradation dynamics and bioactivity assay of the indoxacarb-loaded PU/SA nanoemulsions were determined. Results showed that the obtained indoxacarb-loaded microcapsule particulates were approximately 57 nm in diameter, electronegative -45.9 mV, and uniformly dispersed in the nanoemulsions. The dried latex films of PU/SA in the alkaline environment revealed better responsive swelling and release characteristics than those in acidic and neutral conditions. Compared with a commercial emulsifiable concentrate, the indoxacarb-loaded PU/SA nanoemulsions were useful for the targeted control of S. litura, which have alkaline gut and showed reduced acute contact toxicity to Harmonia axyridia. Furthermore, the PU/SA formulation had better foliage adhesion and indicated the property of controlled-release and a persistent effect.

Droplet Shape and Wetting Behavior under the Influence of Cyclically Changing Humidity

Relative humidity (RH) plays a crucial role in wetting and spreading phenomena by affecting the evaporation rate, evaporation modes, and spreading dynamics via precursor film formation, surface modification, and surface tension alteration. We examined the effect of the periodically varied relative humidity (RH) between low (20%) and high (85%) levels on the wetting of the droplet of nonhygroscopic (pure surfactants) and hygroscopic (ethylene glycol, glycerol) liquids on a hydrophobic surface. It was revealed that the changing RH induces two modes of transition between the wetting states of the droplet: with hysteresis and without hysteresis. Droplets of both nonhygroscopic and hygroscopic liquids exhibit shape hysteresis during the first cycle: (i) droplets of surfactants irreversibly spread saving an initial volume; and (ii) ethylene glycol and glycerol droplets irreversibly absorb the moisture, increasing the volume and the base diameter. Further, cyclically changing the RH results in the droplet breathing effect, i.e., the nonhysteresis transition of the droplet shape between two wetting states corresponding to the minimum and maximum RH levels. In the case of the glycerol droplet for three cycles of the RH variation, the volume hysteresis (the droplet volume increases in each cycle) was observed. This is determined by the moisture absorption due to high hygroscopicity of glycerol. We also revealed that for all liquids studied, the droplet spreading at each increase in RH started at reaching the RH threshold level.

Natural green-peel orange essential oil enhanced the deposition, absorption and permeation of prochloraz in cucumber

Pesticides have long been used in agricultural production and will continue to be used long into the future. Enhancing their efficient use in agricultural production is an effective method to avoid their loss to non-target areas, such as soil, water and air. Here natural green-peel orange essential oil (GOEO) was used as a spray adjuvant to improve the efficient use of pesticides. A comparative study between a conventional formulation and a conventional formulation with GOEO was conducted. Conventional formulations of prochloraz were chosen as control groups. It was obvious that the concentrations of prochloraz and its metabolite in cucumber leaves treated by conventional formulations with GOEO were much higher than those treated without GOEO. The data also showed, for both emulsifiable concentrate (EC) and suspension concentrate (SC), that the spreading and penetration performance were improved when GOEO was used as a spray adjuvant, but with SC the impact was more significant. GOEO improved the deposition, absorption and degradation performance of prochloraz on cucumber leaves. It was more applicable to those pesticide formulations without a good wetting and spreading effect, such as SC. As a plant source extract, GOEO is much safer for crops and more friendly to the environment than other synthetic adjuvants. The application of GOEO as a spray adjuvant has great potential to increase the pesticide utilization rate.

Natural green-peel orange essential oil was used as a spray adjuvant to improve the efficient use of pesticides.

Bounce Behavior and Regulation of Pesticide Solution Droplets on Rice Leaf Surfaces

Pesticide spray droplets can damage ecological environments and negatively affect biodiversity if they reach nontarget areas. Effective retention of pesticide droplets on plant surfaces is an important challenge. In this study, a high-speed camera was utilized to visualize the bounce behavior of droplets of different pesticide solutions on rice leaf surfaces. We explored the addition of surfactants (SAAs) to different pesticide solutions and altered a pesticide solution system to prevent or regulate droplet bounce behavior. Experimental results indicate that the addition of SAAs to a pesticide solution can inhibit the bouncing of droplets on rice leaf surfaces. Additionally, a water-in-oil (EO) emulsion not only can significantly inhibit droplet rebound on a superhydrophobic surface, but also can quickly and automatically spread pesticide droplets to maximize the wetting area. Therefore, this work effectively improves the utilization of pesticides and reduces environmental pollution.