Construction of Lambda-Cyhalothrin Nano-Delivery System with a High Loading Content and Controlled-Release Property

Nanomaterials and Nanotechnology in Agricultural Pesticide Delivery: A Review

Pesticides play a crucial role in ensuring food production and food security. Conventional pesticide formulations can not meet the current needs of social and economic development, and they also can not meet the requirements of green agriculture. Therefore, there is an urgent need to develop efficient, stable, safe, and environmentally friendly pesticide formulations to gradually replace old formulations which have high pollution and low efficacy. The rise of nanotechnology provides new possibilities for innovation in pesticide formulations. Through reasonable design and construction of an environmentally friendly pesticide delivery system (PDS) based on multifunctional nanocarriers, the drawbacks of conventional pesticides can be effectively solved, realizing a water-based, nanosized, targeted, efficient, and safe pesticide system. In the past five years, researchers in chemistry, materials science, botany, entomology, plant protection, and other fields are paying close attention to the research of nanomaterials based PDSs and nanopesticide formulations and have made certain research achievements. These explorations provide useful references for promoting the innovation of nanopesticides and developing a new generation of green and environmentally friendly pesticide formulations. This Perspective summarizes the recent advances of nanomaterials in PDSs and nanopesticide innovation, aiming to provide useful guidance for carrier selection, surface engineering, controlled release conditions, and application in agriculture.

Preparation, Characterization, and Bioactivity Evaluation of Lambda-Cyhalothrin Microcapsules for Slow-Controlled Release System

The utilization of interfacial polymerization in the preparation of microcapsules with a slow-controlled release has been shown to effectively improve pesticide efficacy and reduce environmental pollution. In this study, polyurea microcapsules loaded with lambda-cyhalothrin were prepared by an interfacial polymerization method using modified isocyanate (MDI) as the wall material and GT-34 as the initiator. The microcapsules were fully characterized by optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, etc., and release behaviors were investigated. The results indicated that the microcapsules had a smooth surface and uniform distribution, the average particle size of the microcapsules was 1.97 μm, and the encapsulation efficiency of lambda-cyhalothrin microcapsules could reach 91.48%. Compared with other commercial formulations, the microcapsules exhibited an excellent sustained release property (>7 days) in a 50% acetonitrile aqueous solution (v/v). Subsequently, in vitro release studies showed that the lambda-cyhalothrin microcapsules could consistently control the release of the core materials at different pH, temperature, and MDI addition amount conditions. The release of lambda-cyhalothrin microcapsules was in accordance with the first-order model release, which was mainly by the Fickian diffusion mechanism. Furthermore, the biological activity on Myzus persicae showed that the microcapsules' persistence period was above 21 days, which was longer than that for the emulsifiable concentrate formulation.

pH-responsive release and washout resistance of chitosan-based nano-pesticides for sustainable control of plumeria rust

Controlled pesticide release in response to environmental stimuli by encapsulating pesticides in a carrier is a feasible approach to improve the effective utilization rate. In this study, pH-responsive release nanoparticles loaded with penconazole (PE) were prepared by ionic cross-linking of chitosan and carboxymethyl chitosan (PE@CS/CMCS-NPs). PE@CS/CMCS-NPs exhibited good washout resistance and wettability properties, increasing the washing resistance of the pesticide by approximately 20 times under continuous washing. The results of the release experiments showed that nanoparticles had adjustable controlled-release characteristics with the change in pH based on the swelling of nanoparticles. The results of spore germination experiments showed that PE@CS/CMCS-NPs enhanced the inhibitory effect under acidic conditions. The field experiment results showed that PE@CS/CMCS-NPs had a better control effect than PE-aqueous solution, extended the duration and slowed down the dissipation of PE. These results indicated that the CS/CMCS-NPs pH-responsive release system has great potential in the development of an effective pesticide formulation.

Preparation of Lambda-Cyhalothrin-Loaded Chitosan Nanoparticles and Their Bioactivity against Drosophila suzukii

The encapsulation of pesticides within nanoparticles is a promising approach of advanced technology in sustainable agriculture. Lambda-cyhalothrin (LC) was encapsulated by the ionotropic gelation technique into chitosan (CS)/tripolyphosphate (TPP) and CS/alginate (ALG) matrixes. CS-LC nanoparticles were characterized, and their efficacy was then evaluated against the key pest of soft fruits in Europe and the United States, Drosophila suzukii. The encapsulation efficiency (74%), nanoparticle yield (80%), polydispersity index (0.341), zeta potential (-23.1 mV) and particle size (278 nm) were determined at the optimum conditions. FTIR confirmed the cross-linkage between CS and TPP/ALG in the nanoparticles. The optimum formula recommended by the fractional factorial design was associated with the formulation variables of CS of high or low molecular weight, cross-linking agent (TPP), LC concentration (1.5% w/v) and stirring rate (1500 rpm), showing the highest desirability value (0.5511). CS-LC nanoparticles of the lowest particle size (278 nm) exhibited the highest percent mortality of D. suzukii males (86%) and females (84%), exceeding that caused by the commercial product (Karate-zeon^® 10% CS) at 2 HAT. This is the first work to use the ionic gelation technique to make LC nanoparticles, to the best of our knowledge. The encapsulation of chemical pesticides within biodegradable polymeric nanoparticles could be helpful for establishing a sustainable IPM strategy with benefits for human and environmental health and the lifetime of pesticides.

Stability Phenomena Associated with the Development of Polymer-Based Nanopesticides

Pesticides have been used in agricultural activity for decades because they represent the first defense against pathogens, harmful insects, and parasitic weeds. Conventional pesticides are commonly employed at high dosages to prevent their loss and degradation, guaranteeing effectiveness; however, this results in a large waste of resources and significant environmental pollution. In this regard, the search for biocompatible, biodegradable, and responsive materials has received greater attention in the last years to achieve the obtention of an efficient and green pesticide formulation. Nanotechnology is a useful tool to design and develop “nanopesticides” that limit pest degradation and ensure a controlled release using a lower concentration than the conventional methods. Besides different types of nanoparticles, polymeric nanocarriers represent the most promising group of nanomaterials to improve the agrochemicals’ sustainability due to polymers’ intrinsic properties. Polymeric nanoparticles are biocompatible, biodegradable, and suitable for chemical surface modification, making them attractive for pesticide delivery. This review summarizes the current use of synthetic and natural polymer-based nanopesticides, discussing their characteristics and their most common design shapes. Furthermore, we approached the instability phenomena in polymer-based nanopesticides and strategies to avoid it. Finally, we discussed the environmental risks and future challenges of polymeric nanopesticides to present a comprehensive analysis of this type of nanosystem.

Advances in Controlled-Release Pesticide Formulations with Improved Efficacy and Targetability

Pesticides are commonly used in modern agriculture and are important for global food security. However, postapplication losses due to degradation, photolysis, evaporation, leaching, surface runoff, and other processes may substantially reduce their efficacy. Controlled-release formulations can achieve the permeation-regulated transfer of an active ingredient from a reservoir to a target surface. Thus, they can maintain an active ingredient at a predetermined concentration for a specified period. This can reduce degradation and dissipation and other losses and has the potential to improve efficacy. Recent developments in controlled-release technology have adapted the concepts of intelligence and precision from the pharmaceutical industry. In this review, we present recent advances in the development of controlled-release formulations and discuss details of the preparation methods, material improvements, and application technologies.

Eco-friendly Water-Based λ-Cyhalothrin Polydopamine Microcapsule Suspension with High Adhesion on Leaf for Reducing Pesticides Loss

Recently, innovations of nano/microcarrier formulations have been focused on improving application efficiencies and retention time. In this study, a water-based 2.5% λ-cyhalothrin (LC) microcapsule suspension (CS) was developed by orthogonal test with biodegradable and adhesive polydopamine (PDA) microcapsules (MCs) as carriers. The obtained LC-PDA CS had good suspension properties, flow behavior, storage stability, and rheological properties. LC-PDA CS had higher retention, wettability, and decreased rainwater washing out on the leaves than commercial CS. LC-PDA CS displayed higher insecticidal activity against Lipaphis erysimi compared to commercial CS. LC-PDA CS reduced the toxicity of LC to the aquatic organism Danio rerio compared to LC. The above results demonstrated that LC-PDA CS would be eco-friendly water-based pesticides carrier system for prolonging the retention time on target leaf and reducing toxicity to aquatic organisms.

Preparation and characterization of a novel controlled-release nano-delivery system loaded with pyraclostrobin via high-pressure homogenization

BACKGROUND

The development of efficient and safe green pesticides is a scientific strategy to alleviate current pesticide residues, environmental pollution, and threats to non-target organisms. Pesticide controlled-release formulations (CRFs) have attracted wide attention because they can control the rate of release of active ingredients and prolong the effective duration. In particular, nanoscale pesticide sustained-release systems have excellent biological activity and distribution performance because of their small particle size. Some technical difficulties remain in obtaining nanoscale CRFs.

RESULTS

We successfully fabricated pyraclostrobin nanosphere CRF by combining high-pressure homogenization technology and emulsion-solvent evaporation methods. The pyraclostrobin nanospheres had a uniform spherical shape with a mean particle size of 450 nm and polydispersity index of less than 0.3. The pyraclostrobin loading capacity reached 53.6%, with excellent storage stability. The contact angle of nanospheres on cucumber leaf surfaces demonstrated that it had good wettability. Compared with pyraclostrobin technical and commercial formulations, the nanosphere systems showed a significantly sustained release of pyraclostrobin for longer (up to 250 h). A preliminary bioassay against Penicillium ochrochloron showed that the bioactivity and long-term efficiency of pyraclostrobin nanospheres were superior to those of the commercial formulation.

CONCLUSION

This research introduced a simple, fast, expandable method for preparing pyraclostrobin nanospheres. The results showed that pyraclostrobin nanospheres could prolong the duration of pesticide efficacy and enhance bioactivity. Furthermore, this technology provides a platform for scale-up production of nano-scale pesticide CRFs. © 2020 Society of Chemical Industry.

Dual-Functionalized Pesticide Nanocapsule Delivery System with Improved Spreading Behavior and Enhanced Bioactivity

The prevention and control of pests and diseases are becoming increasingly difficult owing to extensive pesticide resistance. The synergistic use of pesticides for disease control is an effective way of slowing pesticide resistance, reducing the number of pesticide applications, and protecting the environment. In this study, a dual-functionalized pesticide nanocapsule delivery system loaded with two active ingredients (AIs)—validamycin and thifluzamide—was developed to prevent and control rice sheath blight; the nanocapsule system was based on a water–oil–water double emulsion method combined with high-pressure homogenization technology. Our results showed that the dual-functionalized pesticide nanocapsules were monodisperse spheres with a mean particle size of ~260 nm and had good storage stability. Compared with commercial formulations, the dual-functionalized pesticide nanocapsules exhibited good foliar spread owing to their small size, which is beneficial for reducing the loss of pesticides on the leaves. The 50% median effect concentration and synergistic ratio against Rhizoctonia solani of the dual-functionalized pesticide nanocapsules and commercial formulation were 0.0082 and 0.0350 μg/mL, and 2.088 and 0.917, respectively. These findings indicate that the bioactivity of the dual-functionalized system was significantly better than that of the commercial formulations and that the dual-functionalized system demonstrated a clear synergistic effect between the two AIs. The system presented here is simple, fast, and capable of dual-pesticide loading with significant synergistic effects. Our findings could help to facilitate the improvement of pesticides efficiency and the slowing of pesticide resistance.