Antagonistic Effect of Azoxystrobin Poly (Lactic Acid) Microspheres with Controllable Particle Size on Colletotrichum higginsianum Sacc

Preparation of Azoxystrobin-Zinc Metal-Organic Framework/Biomass Charcoal Composite Materials and Application in the Prevention and Control of Gray Mold in Tomato

In order to reduce the use of fungicide and ensure food safety, it is necessary to develop fungicide with low toxicity and high efficiency to reduce residues. Azoxystrobin (AZOX), which is derived from mushrooms, is an excellent choice. However, conventional AZOX release is difficult to regulate. In this paper, a pH-responsive fungicide delivery system for the preparation of AZOX by impregnation method was reported. The Zinc metal-organic framework/Biomass charcoal (ZIF-8/BC) support was first prepared, and subsequently, the AZOX-ZIF-8/BC nano fungicide was prepared by adsorption of AZOX onto ZIF-8/BC by dipping. Gray mold, caused by Botrytis cinerea, is one of the most important crop diseases worldwide. AZOX-ZIF-8/BC could respond to oxalic acid produced by Botrytis cinerea to release loaded AZOX. When pH = 4.8, it was 48.42% faster than when pH = 8.2. The loading of AZOX on ZIF-8/BC was 19.83%. In vitro and pot experiments showed that AZOX-ZIF-8/BC had significant fungicidal activity, and 300 mg/L concentration of AZOX-ZIF-8-BC could be considered as a safe and effective control of Botrytis cinerea. The above results indicated that the prepared AZOX-ZIF-8/BC not only exhibited good drug efficacy but also demonstrated pH-responsive fungicide release.

Biobased, Macro-, and Nanoscale Fungicide Delivery Approaches for Plant Fungi Control

In this report, two polymeric matrix systems at macro and nanoscales were prepared for efficacious fungicide delivery. The macroscale delivery systems used millimeter-scale, spherical beads composed of cellulose nanocrystals and poly(lactic acid). The nanoscale delivery system involved micelle-type nanoparticles, composed of methoxylated sucrose soyate polyols. Sclerotinia sclerotiorum (Lib.), a destructive fungus affecting high-value industrial crops, was used as a model pathogen against which the efficacy of these polymeric formulations was demonstrated. Commercial fungicides are applied on plants frequently to overcome the transmission of fungal infection. However, fungicides alone do not persist on the plants for a prolonged period due to environmental factors such as rain and airflow. There is a need to apply fungicides multiple times. As such, standard application practices generate a significant environmental footprint due to fungicide accumulation in soil and runoff in surface water. Thus, approaches are needed that can either increase the efficacy of commercially active fungicides or prolong their residence time on plants for sustained antifungal coverage. Using azoxystrobin (AZ) as a model fungicide and canola as a model crop host, we hypothesized that the AZ-loaded macroscale beads, when placed in contact with plants, will act as a depot to release the fungicide at a controlled rate to protect plants against fungal infection. The nanoparticle-based fungicide delivery approach, on the other hand, can be realized via spray or foliar applications. The release rate of AZ from macro- and nanoscale systems was evaluated and analyzed using different kinetic models to understand the mechanism of AZ delivery. We observed that, for macroscopic beads, porosity, tortuosity, and surface roughness governed the efficiency of AZ delivery, and for nanoparticles, contact angle and surface adhesion energy were directing the efficacy of the encapsulated fungicide. The technology reported here can also be translated to a wide variety of industrial crops for fungal protection. The strength of this study is the possibility of using completely plant-derived, biodegradable/compostable additive materials for controlled agrochemical delivery formulations, which will contribute to reducing the frequency of fungicide applications and the potential accumulation of formulation components in soil and water.

Construction and Characterization of Novel Hydrophilic Nanospheres Loaded with Lambda-Cyhalothrin via Ultrasonic Emulsification-Solvent Evaporation

Safe and efficient pesticide formulations have attracted great attention for the prevention and control of diseases and pests. In recent years, improving the effectiveness and duration of pesticides through nanotechnology has become a research hotspot in the field of pesticide formulations. Here, we develop a novel hydrophilic lambda-cyhalothrin nanospheres encapsulated with poly(styrene-co-maleic anhydride) (PSMA) via the ultrasonic emulsification-solvent evaporation method, which exhibited better particle size uniformity and dispersion in comparison with the traditional method. The effects of PSMA content, oil phase/water phase ratio and phacoemulsification time on the particle size and morphology of nanoparticles were investigated to optimize preparation process parameters. Meanwhile, the wettability and adhesion behavior on the leaf surface, the release properties, and the storage stability of nanoparticles were characterized to evaluate the performance of the novel nano-formulation. This work not only establishes a facile and promising method for the applicable of insoluble pesticides, but also develops an innovative nano-formulation with hydrophilicity and high leaf adhesion, which opens a new direction in plant protection and residue reduction.

Advances in Biopolymeric Nanopesticides: A New Eco-Friendly/Eco-Protective Perspective in Precision Agriculture

Pesticides are essential to contemporary agriculture and are required to safeguard plants from hazardous pests, diseases, and weeds. In addition to harming the environment, overusing these pesticides causes pests to become resistant over time. Alternative methods and agrochemicals are therefore required to combat resistance. A potential solution to pesticide resistance and other issues may be found in nanotechnology. Due to their small size, high surface-area-to-volume ratio, and ability to offer novel crop protection techniques, nanoformulations, primarily biopolymer-based ones, can address specific agricultural concerns. Several biopolymers can be employed to load pesticides, including starch, cellulose, chitosan, pectin, agar, and alginate. Other biopolymeric nanomaterials can load pesticides for targeted delivery, including gums, carrageenan, galactomannans, and tamarind seed polysaccharide (TSP). Aside from presenting other benefits, such as reduced toxicity, increased stability/shelf life, and improved pesticide solubility, biopolymeric systems are also cost-effective; readily available; biocompatible; biodegradable; and biosafe (i.e., releasing associated active compounds gradually, without endangering the environment) and have a low carbon footprint. Additionally, biopolymeric nanoformulations support plant growth while improving soil aeration and microbial activity, which may favor the environment. The present review provides a thorough analysis of the toxicity and release behavior of biopolymeric nanopesticides for targeted delivery in precision crop protection.

Degradable Poly(3-hydroxybutyrate)-The Basis of Slow-Release Fungicide Formulations for Suppressing Potato Pathogens

Three-component slow-release fungicide formulations with different modes of action of the active ingredients for suppressing potato pathogens were constructed for the first time. The difenoconazole, mefenoxam, prothioconazole, and azoxystrobin fungicides were embedded in the degradable polymer P(3HB)/birch wood flour blend and examined using SEM, IR spectroscopy, X-ray analysis, DTA, and DSC. Results showed that no chemical bonds were established between the components and that they were physical mixtures that had a lower degree of crystallinity compared to the initial P(3HB), which suggested different crystallization kinetics in the mixtures. The degradation behavior of the experimental formulations was investigated in laboratory micro-ecosystems with pre-characterized field soil. The slow-release fungicide formulations were prolonged-action forms with a half-life of at least 50–60 d, enabling gradual and sustained delivery of the active ingredients to plants. All slow-release fungicide formulations had a strong inhibitory effect on the most common and harmful potato pathogens (Phytophthorainfestans, Alternarialongipes, Rhizoctoniasolani, and Fusariumsolani).

Polylactic acid nanoparticles for co-delivery of dinotefuran and avermectin against pear tree pests with improved effective period and enhanced bioactivity

Pesticide compounding technology for disease and pest control emerges as an effective way to increase the effectiveness of pesticides while reducing pesticides resistance. Nanomaterials and encapsulation technology have offered a new insight into preparing efficient pesticide formulations, especially constructing a co-delivery nanoparticle for synergistic pesticides. In this study, a dinotefuran/avermectin co-delivery nanoparticles (DACNPs) against pear tree pests with polylactic acid (PLA) as the wall material were constructed by double-emulsion method combined with high-pressure homogenization technique. The drug content of the DACNPs was 39.1% with an average size of 245.7 ± 4.2 nm and the mean polymer dispersity index (PDI) value was 0.123. The DACNPs showed high foliar retention and good spread performance on target leaves due to the nanoscale effect. The obtained DACNPs showed a better control effect on Grapholitha molesta Busck and Psylla chinensis Yang et Li compared with the commercial formulations, which could significantly prolong the effective duration and enhance the bioactivity with lower amounts and application frequency of pesticides. This study may provide new insights into developing novel pesticide formulations to improve the utilization rate of pesticides, reduce environmental pollution and minimize the cost of farming.

Surface-modified polylactic acid nanospheres with chitosan for antibacterial activity of 1, 2-benzisothiazolin-3-one

The primary purpose of this study was to develop an innovative chitosan (CS) modified polylactic acid (PLA) nanospheres for enhancing the bioavailability of 1, 2-benzisothiazolin-3-one (BIT). The cellular uptake efficiency was corresponded positively to the quantity of CS coated on BIT-PLA nanospheres against E. coli and S. aureus. The membrane potentials of E.coli and S. aureus treated with BIT-PLA, BIT-PLA-0.1%CS and BIT-PLA-0.5%CS were reduced with the extension of incubation time and the ratio of coated CS. The enhancement of CS modified on BIT-PLA nanospheres was reduced antioxidase activities and generated excessive reactive oxygen species. The lowest EC₅₀ value of the modified BIT-PLA-0.5%CS suggested that its toxicity index was around 2.95-fold and 2.11-fold that of non-modified BIT-PLA against E. coli and S. aureus, respectively. These results revealed that the CS modified BIT-PLA nanospheres had a bright prospect in antibacterial formulation delivery system and improving the bioavailability.

Preparation and Size Control of Efficient and Safe Nanopesticides by Anodic Aluminum Oxide Templates-Assisted Method

Efficient and safe nanopesticides play an important role in pest control due to enhancing target efficiency and reducing undesirable side effects, which has become a hot spot in pesticide formulation research. However, the preparation methods of nanopesticides are facing critical challenges including low productivity, uneven particle size and batch differences. Here, we successfully developed a novel, versatile and tunable strategy for preparing buprofezin nanoparticles with tunable size via anodic aluminum oxide (AAO) template-assisted method, which exhibited better reproducibility and homogeneity comparing with the traditional method. The storage stability of nanoparticles at different temperatures was evaluated, and the release properties were also determined to evaluate the performance of nanoparticles. Moreover, the present method is further demonstrated to be easily applicable for insoluble drugs and be extended for the study of the physicochemical properties of drug particles with different sizes.

Encapsulation of fluazinam to extend efficacy duration in controlling Botrytis cinerea on cucumber

BACKGROUND

Fluazinam is an effective fungicide in controlling gray mold, but has short duration of efficacy. Increasing application dosage may cause phytotoxicity. To overcome this shortage, a controlled-release technology was studied by encapsulating fluazinam. Ethyl cellulose polymer microcapsules were loaded with fluazinam to formulate a fluazinam capsule suspension (FCS). The efficacy for inhibition of B. cinerea and persistency of the FCS were examined by comparing with fluazinam technical concentrate (FTC) and aqueous fluazinam suspension concentrate (FSC) using microscopic observation and high-performance liquid chromatography analysis.

RESULTS

FCS formed capsules, with median size of 3.17 μm in diameter, had 82.3% encapsulation efficiency. It had a stronger inhibitory activity against B. cinerea than FTC and FSC measured 7 days after the treatments. The half-life of FCS on cucumber leaves was 3.4 days, longer than the 2.3 days of FSC.

CONCLUSION

FCS formulation significantly improved the inhibition of B. cinerea and resulted in prolonged and sustained release. Moreover, microencapsulation increased the duration of the efficacy of fluazinam on target crops. This formulation could help to sustain pesticides and protect the environment. © 2021 Society of Chemical Industry.

An improved solvent evaporation method to produce poly (lactic acid) microspheres via foam-transfer

The aim of this work was to study an improved solvent evaporation method to prepare poly (lactic acid) (PLA) microspheres via foam-transfer. Since the foaming process and its transfer were critical to the improved method, they have been studied. Additionally, the delivery capability of foams was studied as a function of the oil/water ratio, the stirring rate, the concentration of polyvinyl alcohol (PVA) and ethanol (EtOH) in the aqueous phase (ω_PVA, ω_EtOH). It was found that foaming varied during the preparation process and it influenced the properties of PLA microspheres. When the oil/water ratio (w/w) ≥ 3:10, stirring rate ≥ 600 r/min, ω_PVA ≥ 1 wt%, and ω_EtOH = 0 wt%, solvent evaporation was able to produce enough foams for foam-transfer, which helped to deliver more than 89 wt% PLA microspheres to the receiving vessel. However, ω_PVA ≤ 0.3 wt% and ω_EtOH = 20 wt% were unfavorable for maintaining the spherical shape of PLA microspheres and caused the aggregation. The methodology was further used to prepare azoxystrobin-loaded PLA microspheres successfully with a high encapsulation efficiency of 86.54%. This work is meaningful since it enables an efficient and continuous route to prepare functional biodegradable polymer microspheres.

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.

Recent advances and remaining barriers to producing novel formulations of fungicides for safe and sustainable agriculture

BACKGROUND

Fungi have evolved for 1 billion years and due to their adaptability and resilience can be found in multiple habitats around the globe. Among numerous species of fungi, some are pathogenic, and humans have battled since the dawn of organized agriculture to reduce production losses. With the arrival of fungicides many gains have been made in this struggle. However, though fungicides have greatly contributed to substantial increase in agricultural productivity, their over usage has led to both health and environmental repercussions. They remain cornerstone of the agriculture industry, however, development of safer formulations to champion sustainable and eco-friendly agriculture is of great importance, especially in face of a growing global population, climate change and increasing fungal resistance to existing compounds.

SCOPE AND APPROACH

The aim of this review is to present the state of the art in fungicides formulations developed for agrochemistry, also describing recent improvements in their safety, with special focus on fungicides used most against the ten most important fungal pathogens.

KEY FINDINGS AND CONCLUSIONS

The major focus in the field remains to be the improvement of the overall performance of the fungicide formulations. The research trends are also moving towards developing more eco-friendly formulations. However, there are still very few studies assessing nanoformulations toxicity and environmental impact. For example, there is still a limited body of research on the holistic assessment of nanoformulation shells' fate in soil and in the environment after release, as well as redistribution within plants after absorption, with no studies on human or environmental exposure.

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.

Constructing Slow-Release Fungicide Formulations Based on Poly(3-hydroxybutyrate) and Natural Materials as a Degradable Matrix

Slow-release fungicide formulations (azoxystrobin, epoxiconazole, and tebuconazole) shaped as pellets and granules in a matrix of biodegradable poly(3-hydroxybutyrate) and natural fillers (clay, wood flour, and peat) were constructed. Infrared spectroscopy showed no formation of chemical bonds between components in the experimental formulations. The formulations of pesticides had antifungal activity against Fusarium verticillioides in vitro. A study of biodegradation of the experimental fungicide formulations in the soil showed that the degradation process was mainly influenced by the type of formulation without significant influence of the type of filler. More active destruction of the granules led to a more rapid accumulation of fungicides in the soil. The content of fungicides present in the soil as a result of degradation of the formulations and fungicide release was determined by their solubility. Thus, all formulations are able to function in the soil for a long time, ensuring gradual and sustained delivery of fungicides.