Pectin-Coated Iron-Based Metal-Organic Framework Nanoparticles for Enhanced Foliar Adhesion and Targeted Delivery of Fungicides.

Conventional agrochemicals are underutilized due to their large particle sizes, poor foliar retention rates, and difficult translocation in plants, and the development of functional nanodelivery carriers with high adhesion to the plant body surface and efficient uptake and translocation in plants remains challenging. In this study, a nanodelivery system based on a pectin-encapsulated iron-based MOF (TF@Fe-MOF-PT NPs) was constructed to enhance the utilization of thifluzamide (TF) in rice plants by taking advantage of the pectin affinity for plant cell walls. The prepared TF@Fe-MOF-PT NPs exhibited an average particle size of 126.55 nm, a loading capacity of 27.41%, and excellent dual-stimulus responses to reactive oxygen species and pectinase. Foliar washing experiments showed that the TF@Fe-MOF-PT NPs were efficiently adhered to the surfaces of rice leaves and stems. Confocal laser scanning microscopy showed that fluorescently labeled TF@Fe-MOF-PT NPs were bidirectionally delivered through vascular bundles in rice plants. The in vitro bactericidal activity of the TF@Fe-MOF-PT NPs showed better inhibitory activity than that of a TF suspension (TF SC), with an EC50 of 0.021 mg/L. A greenhouse test showed that the TF@Fe-MOF-PT NPs were more effective than TF SC at 7 and 14 d, with control effects of 85.88 and 78.59%, respectively. It also reduced the inhibition of seed stem length and root length by TF SC and promoted seedling growth. These results demonstrated that TF@Fe-MOF-PT NPs can be used as a pesticide nanodelivery system for efficient delivery and intelligent release in plants and applied for sustainable control of pests and diseases.

Long-term toxic effects of iron-based metal-organic framework nanopesticides on earthworm-soil microorganism interactions in the soil environment.

With the widespread use of controlled-release nanopesticides in field conditions, the interactions between these nanopesticides and biological systems are complex and highly uncertain. The toxicity of iron-based metal organic frameworks (CF@MIL-101-SL) loaded with chlorfenapyr (CF) to terrestrial invertebrate earthworms in filter paper and soil environments and the potential mechanisms of interactions in the nanopesticide-earthworm-cornfield soil microorganism system were investigated for the first time. The results showed that CF@MIL-101-SL was more poisonous to earthworms in the contact filter paper test than suspension concentrate of CF (CF-SC), and conversely, CF@MIL-101-SL was less poisonous to earthworms in the soil test. In the soil environment, the CF@MIL-101-SL treatment reduced oxidative stress and the inhibition of detoxifying enzymes, and reduced tissue and cellular substructural damage in earthworms compared to the CF-SC treatment. Long-term treatment with CF@MIL-101-SL altered the composition and abundance of microbial communities with degradative functions in the earthworm intestine and soil and affected the soil nitrogen cycle by modulating the composition and abundance of nitrifying and denitrifying bacterial communities in the earthworm intestine and soil, confirming that soil microorganisms play an important role in reducing the toxicity of CF@MIL-101-SL to earthworms. In conclusion, this study provides new insights into the ecological risks of nanopesticides to soil organisms.

Genomic and co-expression network analyses reveal candidate genes for oil accumulation based on an introgression population in Upland cotton (Gossypium hirsutum).

KEY MESSAGE: Integrated QTL mapping and WGCNA condense the potential gene regulatory network involved in oil accumulation. A glycosyl hydrolases gene (GhHSD1) for oil biosynthesis was confirmed in Arabidopsis, which will provide useful knowledge to understand the functional mechanism of oil biosynthesis in cotton. Cotton is an economical source of edible oil for the food industry. The genetic mechanism that regulates oil biosynthesis in cottonseeds is essential for the genetic enhancement of oil content (OC). To explore the functional genomics of OC, this study utilized an interspecific backcross inbred line population to dissect the quantitative trait locus (QTL) interlinked with OC. In total, nine OC QTLs were identified, four of which were novel, and each QTL explained 3.62-34.73% of the phenotypic variation of OC. The comprehensive transcript profiling of developing cottonseeds revealed 3,646 core genes differentially expressed in both inbred parents. Functional enrichment analysis determined 43 genes were annotated with oil biosynthesis processes. Implementation of weighted gene co-expression network analysis showed that 803 differential genes had a significant correlation with the OC phenotype. Further integrated analysis identified seven important genes located in OC QTLs. Of which, the GhHSD1 gene located in stable QTL qOC-Dt3-1 exhibited the highest functional linkages with the other network genes. Phylogenetic analysis showed significant evolutionary differences in the HSD1 sequences between oilseed- and starch- crops. Furthermore, the overexpression of GhHSD1 in Arabidopsis yielded almost 6.78% higher seed oil. This study not only uncovers important genetic loci for oil accumulation in cottonseed, but also provides a set of new candidate genes that potentially influence the oil biosynthesis pathway in cottonseed.

Efficacy of drip irrigation with thiamethoxam on control of Monolepta hieroglyphica, and uptake, translocation and dietary risk of thiamethoxam in maize.

BACKGROUND: Monolepta hieroglyphica (Motschulsky) is an important agricultural pest that causes significant economic losses in terms of crop production. Conventional pesticide spraying treatments can result in pesticide drift, endanger nontarget organisms and cause pests to fly away, resulting in unsatisfactory prevention and control effects. To study the effect of thiamethoxam on the control of maize M. hieroglyphica, a field experiment was conducted to determine the optimal thiamethoxam application dose, its spatial and temporal distribution dynamics, and its dietary risk based on its control effect when applied by spray and drip irrigation. RESULTS: The results of the field trials showed that compared with spray irrigation, drip irrigation resulted in greater control starting from Day 5. This result was a consequence of the hysteresis effect of thiamethoxam being first absorbed by the roots and then continuously transferred upward, where it accumulates. After 30 days of drip irrigation with 75 and 150 g a.i. ha-1 thiamethoxam, the control effect on M. hieroglyphica was 32.41-49.44% and 69.77-80.57%, respectively. The results of the dietary risk assessment showed that the risk of thiamethoxam ingestion through maize kernels was acceptable regarding its effect on human health. CONCLUSIONS: Drip irrigation with thiamethoxam can improve the effective utilization rate of pesticides, achieve precise control of maize M. hieroglyphica, and provide a new method for sustainable agricultural production. © 2023 Society of Chemical Industry.

Enhanced Insecticidal Activity of Chlorfenapyr against Spodoptera frugiperda by Reshaping the Intestinal Microbial Community and Interfering with the Metabolism of Iron-Based Metal-Organic Frameworks.

Spodoptera frugiperda (S. frugiperda) is an invasive pest that threatens global crop production and food security and poses a serious threat to maize production worldwide. Metal-organic framework (MOF) nanocarriers have great potential for agricultural pest control applications. The present study successfully prepared the chemical cross-linking of iron-based metal-organic framework nanoparticles (MIL-101(Fe)-NH2 NPs) with sodium lignosulfonate (SL) as a pH/laccase double stimuli-responsive pesticide release system. The average particle size of the prepared chlorfenapyr (CF)-loaded nanoparticles (CF@MIL-101-SL NPs) was 161.54 nm, and the loading efficiency was 44.52%. Bioactivity assays showed that CF@MIL-101-SL NPs increased the toxicity of CF to S. frugiperda and caused the rupture of the peritrophic membrane and enlargement of the midgut. Data from 16S rRNA gene sequencing showed that CF@MIL-101-SL treatment reduced the resistance of S. frugiperda to pesticides and pathogens and affected nutrient and energy availability by remodeling the intestinal microbiota of S. frugiperda. The dysregulated microbial community interacted with the broken peritrophic membrane, which exacerbated damage to the host. Nontargeted metabolomic results showed that ABC transporters may be a potential mechanism for the enhanced toxicity of CF@MIL-101-SL to S. frugiperda. In summary, the present study provides effective strategies for toxicological studies of nanopesticides against insects.

Rotenone encapsulated in pH-responsive alginate-based microspheres reduces toxicity to zebrafish.

Rotenone is a botanical pesticide and has long been used for control of insect pests and also as a natural piscicide for management of fish populations in many countries. Field application for pest control, however, often encounters the movement of rotenone into surface water due to spray drift or surface runoff after rainfall, which could potentially result in water pollution and unexpected death of fishes. To minimize its effect on freshwater and the problem of fish dying, one solution was to encapsulate rotenone in specific microspheres, limiting its release and reducing its toxicity since rotenone can be quickly degraded under sunlight. In this study, pH-responsive alginate-based microspheres were synthesized to encapsulating rotenone, which were designated as rotenone beads. The rotenone beads, along with alginate beads (devoid of rotenone) were characterized and evaluated for their responses to pH and effects on zebrafish. Results showed that the microspheres had high loading efficiency (4.41%, w/w) for rotenone, and rotenone beads well responded to solution pH levels. The cumulative release rates of rotenone from the beads were 27.91%, 42.72%, and 90.24% at pH 5.5, 7.0, and 9.0, respectively. Under acidic conditions, the rotenone release rate was lower due to hydrogen bonding. On the contrary, rotenone became more quickly released at the high pH due to intermolecular repulsion. The toxicity of rotenone beads to zebrafish and fish embryos at a pH of 5.5 was reduced by 2- and 4-fold than chemical rotenone. Since pH levels in most freshwater lakes, ponds, and streams vary from 6 to 8, rotenone release from the beads in such freshwater could be limited. Thus, the synthesized rotenone beads could be relatively safely used for pest control with limited effects on freshwater fishers.

Effect of bifenthrin application at different maturity stages on its dissipation and residues in kumquat (Citrus japonica) and dietary intake risk assessment.

Bifenthrin is a pyrethroid pesticide widely used on kumquats, but the residues in the peel and pulp after bifenthrin application at different maturity stages of kumquats have not been evaluated. This study developed a simple and rapid high-performance liquid chromatography (HPLC) method for the quantitative analysis of bifenthrin residues in whole fruit, kumquat peel, kumquat pulp, and soil. The results showed that regardless of whether bifenthrin was applied one or three times during the near-mature period, the half-lives of the fruit peel and fruit pulp were longer than those in the immature period. Kumquat fruit residues decreased with time at both maturity levels. The residues of bifenthrin in near-mature fruit exceeded the MRL in Guangxi and Fujian 14 days after the three applications of bifenthrin, suggesting that this issue should be focused on in kumquat production and supervision. However, for bifenthrin application in either the near-mature or the immature fruit period, the calculated risks for chronic dietary intake of kumquat were well below 100%. The data demonstrate that the chronic dietary intake risk of bifenthrin through kumquat consumption is low and within acceptable limits. These results provide a reference and risk assessment data for the safe and rational use of bifenthrin insecticides.

ß-Glucan-Functionalized Mesoporous Silica Nanoparticles for Smart Control of Fungicide Release and Translocation in Plants.

In this work, an enzyme-responsive nanovehicle for improving captan (CAP) contact fungicide bioactivity and translocation in plant tissues was synthesized (CAP-MSNs-ß-glucan) by attaching ß-glucan to the outer surface of mesoporous silica nanoparticles. CAP-MSNs-ß-glucan properties were tested by FTIR, ζ-potential, DLS, XRD, TGA, FE-SEM, and HR-TEM. Cargo protection ability of CAP-MSNs-ß-glucan from photolysis and hydrolysis was examined in comparison to CAP commercial formulation (CAP-CF). CAP-MSNs-ß-glucan distribution in plant tissues, bioactivity against Fusarium graminearum, and biotoxicity toward zebrafish (Danio rerio) were tested and compared with that of CAP-CF. CAP-MSNs-ß-glucan results showed good loading efficacy reaching 18.39% and enzymatic-release dependency up to 83.8% of the total cargo after 20 days of ß-glucan unsealing. CAP-MSNs-ß-glucan showed significant release protection under pH changes. MSNs-ß-glucan showed excellent CAP protection from UV. CAP-MSNs-ß-glucan showed better distribution in corn tissues and 1.28 more inhibiting potency to Fusarium graminearum than CAP-CF. CAP-MSNs-ß-glucan showed 1.88 times lower toxicity than CAP-CF to zebrafish after 96 h of treatment. We recommend using such formulations to overcome shortcomings of contact fungicides and achieve better and sustainable farming.

A pH- and redox-stimulated responsive hollow mesoporous silica for triggered delivery of fungicides to control downy mildew of Luffa cylindrica.

BACKGROUND: Downy mildew, a devastating disease of cucurbitaceous crops caused by Pseudoperonospora cubensis. Although a variety of fungicides are used to control downy mildew, choosing an effective product can be challenging. Environmental stimulus-responsive pesticide delivery systems have great potential to improve the effectiveness of disease and pest control and reduce the impact on environmentally beneficial organisms. RESULTS: In this work, a disulfide bond (SS)-modified and chitosan oligosaccharide (COS)-capped hollow mesoporous silica (HMS) pesticide delivery system was synthesized using a hard template method for the control of downy mildew in cucurbit crops. The synthesized nanoparticles were loaded with dimethomorph (DMM), denoted as DMM@HMS-SS-COS, and the developmental toxicity of these nanoparticles to zebrafish embryos were evaluated. The results showed that the prepared DMM@HMS-SS-COS exhibited excellent dual response properties to pH and glutathione (GSH), with an encapsulation rate of up to 24.36%. DMM@HMS-SS-COS has good ultraviolet (UV) radiation stability and adhesion properties. Compared with dimethomorph suspension concentrate (SC), DMM@HMS-SS-COS was more effective against downy mildew for up to 21 days. Toxicity tests showed that DMM@HMS-SS-COS significantly reduced the effect of DMM on the hatching rate and survival rate of zebrafish embryos. CONCLUSIONS: This work not only demonstrates that DMM@HMS-SS-COS could be used as a nanodelivery system for intelligent control of downy mildew but also emphasizes the necessity of increasing the acute toxicity of nanoformulations to non-target organisms in environmental risk assessment. © 2022 Society of Chemical Industry.

Efficiency of mesoporous silica/carboxymethyl ß-glucan as a fungicide nano-delivery system for improving chlorothalonil bioactivity and reduce biotoxicity.

Understanding the lethal effects of pesticides nano formulations on the targeted organisms (pathogens) and the non-targeted organisms (fish, earthworms, etc) is essential in assessing the probable impact of new technologies on agriculture and environment. Here we evaluated the bioactivity and the biotoxicity of new type of fungicide smart-delivery formulation based on conjugating carboxymethylated-ß-glucans on the mesoporous silica nanoparticles (MSNs) surface after loading chlorothalonil (CHT) fungicide in the MSNs pores. The obtained formulation has been characterized with FE-SEM, and HR-TEM. The CHT loading efficiency has been measured with TGA. The bioactivity of the obtained formulation (CHT@MSNs-ß-glucans) has been tested against four pathogens, fusarium head blight (Fusarium graminearum), sheath rot (Sarocladium oryzae), rice sheath blight (Rhizoctonia solani), and soyabean anthracnose (Colletotrichum truncatum) compared with CHT WP 75% commercial formulation (CHT-WP) and technical CHT. The environmental biotoxicity of CHT@MSNs-ß-glucans compared with CHT-WP has been tested toward earthworm (Eisenia fetida) and zebra fish (Danio rerio). The results showed that CHT@MSNs-ß-glucans has an excellent bioactivity against the subjected pathogens with better inhabiting effects than CHT-WP. CHT@MSNs-ß-glucans toxicity to Eisenia fetida was found 2.25 times lower than CHT-WP toxicity. The LC50 of CHT@MSNs-ß-glucans to zebra fish after the first 24h was 2.93 times higher than CHT-WP. After 96h of treatment, the LC50 of CHT@MSNs-ß-glucans was 2.66 times higher than CHT-WP. This work highlighted the necessity to increase the mandatory bioassays of nano formulations with the major non-target organisms in the environmental risk assessment of new pesticide formulations.

Floating chitosan-alginate microspheres loaded with chlorantraniliprole effectively control Chilo suppressalis (Walker) and Sesamia inferens (Walker) in rice fields.

Striped rice stem borer, Chilo suppressalis (Walker) and pink stem borer, Sesamia inferens (Walker) are two important pests, causing substantial yield loss in rice production. Application of conventional synthetic pesticides, such as suspension concentrates and water-dispersible granules, is a primary method for control of the two pests. Due to the flow of water in rice field, spray drift, and soil adsorption, applied such pesticides are often out of the target, resulting in low control efficacy, potential contamination of soil or surface water, and also threat to human health. Thus, there is an urgent need for developing environmentally friendly and highly targeted pesticide formulations to meet the challenges. The present study synthesized chlorantraniliprole loaded chitosan-alginate floating hydrogel microspheres (CCAM) through physical embedding, ionic crosslinking, and incorporation of citronellol as an oil phase. The morphology, particle size, entrapment efficiency, loading capacity, in vitro slow-release kinetics, and floating ability of the CCAM were tested in laboratory conditions. The CCAM and two commercial formulations (suspended and granulated) of chlorantraniliprole were respectively evaluated in two rice fields located in two provinces of China. The CCAM was able to float on the surface of rice field, gather around rice stems, and slowly release chlorantraniliprole, which resulted in significantly higher concentrations of chlorantraniliprole in rice stems and leaves for a prolonged time than suspended and granulated controls. The application of CCAM provided an on-target control of both striped stem borer and pink stem borer. Furthermore, CCAM application had very low residue of chlorantraniliprole in soils. As far as is known, this is the first report of chlorantraniliprole loaded on chitosan-alginate floating hydrogel microspheres for rice stem borer control. Our results indicate that the synthesized CCAM could potentially be used as a controlled-release product for effective control of the two rice pests, while reducing the residual chlorantraniliprole in the soil and avoiding pesticide drift.

Carboxylated ß-cyclodextrin anchored hollow mesoporous silica enhances insecticidal activity and reduces the toxicity of indoxacarb.

In this study, a pesticide controlled release system with dual response characteristics of pH and enzyme triggering was developed. Indoxacarb (IDC) was loaded into hollow mesoporous silica (HMS) nanoparticles, carboxylated ß-cyclodextrin (ß-CD) acted as a capping molecule to couple with the amino-functionalized HMS, and their well-defined morphological structures were confirmed by scanning electron microscopy and transmission electron microscopy. The results showed that the prepared IDC loaded HMS-CD had high loading efficiency (26.42%, w/w) and showed excellent dual response properties to pH and the α-amylase enzyme. IDC loaded HMS-CD nanoparticles showed better insecticidal activity against Spodoptera frugiperda than applying the same dose of IDC emulsifiable concentrate, and the toxicity of IDC loaded HMS-CD to zebrafish was reduced by more than 5-fold, indicating that insecticide delivery systems based on ß-CD-anchored HMS nanoparticles could potentially be applied for sustainable control of pests and reduce harm to non-target organisms and the environment.

Preparation of alginate-chitosan floating granules loaded with 2-methyl-4-chlorophenoxy acetic acid (MCPA) and their bioactivity on water hyacinth.

BACKGROUND: Water hyacinth (Eichhornia crassipes) is considered the most damaging aquatic weed in many countries. Chemical methods are still the primary approach to control, although this directly exposes the natural enemy of water hyacinth (water hyacinth weevil) to herbicides. In addition, spray drift can easily damage non-target plants. In this study, herbicides, natural polymer materials (chitosan and carboxymethyl chitosan), sodium alginate and natural oils (citronella oil) were used to prepare novel floating polysaccharide granules as a solution for controlling water hyacinth. RESULTS: 2-Methyl-4-chlorophenoxy acetic acid (MCPA) floating granules with a spherical structure were prepared using a MCPA-chitosan-sodium alginate-oil cross-linking and embedding method. The granules produced showed the required properties of floatation and slow controlled herbicide release. In addition, the polysaccharide granules collected around water hyacinth plants and enabled targeted release of the active herbicide ingredients onto the stems and roots of the weed, thereby stopping the herbicide from reaching non-target plants and preventing regrowth of water hyacinth. CONCLUSION: We successfully prepared highly effective MCPA-loaded floating granules, which compared with an MCPA solution, exerted greater control on water hyacinth. Concomitantly, these granules provide a solution to spray drift and ensure the safety of natural enemies of water hyacinth, which is of great significance in research on herbicide formulations.

Insecticidal efficacy and mechanism of nanoparticles synthesized from chitosan and carboxymethyl chitosan against Solenopsis invicta (Hymenoptera: Formicidae).

The efficacy and mode of action of biodegradable chitosan (CS) and carboxymethyl chitosan (CMCS) organic polymer nanoparticles (NPs) on insects were studied. The prepared CS/CMCS-NPs were spherical with a particle size of 142.1 ± 2.0 nm. The swelling test showed that they were pH-sensitive, and the swelling rate was 554 % at pH 4.5. It was found that CS/CMCS-NPs had insecticidal efficacy against red fire ants (S. invicta). The mortality of red fire ants on the 6th day after treatment with 0.2 % and 0.06 % CS/CMCS-NPs suspensions was 98.33 ± 1.67 % and 48.33 ± 3.33 %, respectively. After CS/CMCS-NPs treatment, the food intake, growth, and development of red fire ants were inhibited; the midgut was significantly expanded; and the activity of digestive enzymes in the midgut was decreased. Our findings suggest that CS/CMCS-NPs mainly inhibited the digestion function of the midgut, leading to the death of red fire ants.

Toxicity and Sublethal Effects of Autumn Crocus (Colchicum autumnale) Bulb Powder on Red Imported Fire Ants (Solenopsis invicta).

Autumn crocus (Colchicum autumnale L.) is a medicinal plant as it contains high concentrations of colchicine. In this study, we reported that the ground powder of autumn crocus bulb is highly toxic to invasive Solenopsis invicta Buren, commonly referred to as red imported fire ants (RIFAs). Ants fed with sugar water containing 5000 mg/L of bulb powder showed 54.67% mortality in three days compared to 45.33% mortality when fed with sugar water containing 50 mg/L of colchicine. Additionally, the effects of short-term feeding with sugar water containing 1 mg/L of colchicine and 100 mg/L of autumn crocus bulb powder were evaluated for RIFAs' colony weight, food consumption, and aggressiveness, i.e., aggregation, grasping ability, and walking speed. After 15 days of feeding, the cumulative colony weight loss reached 44.63% and 58.73% due to the sublethal concentrations of colchicine and autumn crocus bulb powder, respectively. The consumption of sugar water and mealworm (Tenebrio molitor L.) was substantially reduced. The aggregation rates decreased 48.67% and 34.67%, grasping rates were reduced to 38.67% and 16.67%, and walking speed decreased 1.13 cm/s and 0.67 cm/s as a result of the feeding of the two sublethal concentrations of colchicine and autumn crocus bulb powder, respectively. Our results for the first time show that powder derived from autumn crocus bulbs could potentially be a botanical pesticide for controlling RIFAs, and application of such a product could be ecologically benign due to its rapid biodegradation in the environment.

Preparation of sodium alginate-poly (vinyl alcohol) blend beads for base-triggered release of dinotefuran in Spodoptera litera midgut.

This study investigated the ability of dual crosslinked interpenetrating polymer network (IPN) blend beads (DIN:SA/PVA-beads), composed of sodium alginate (SA) and poly (vinyl alcohol) (PVA), as a base-triggered carrier for the controlled release of dinotefuran (DIN) in Spodoptera litera midgut. The blend beads were characterized for morphology, encapsulation efficiency, swelling degree, and in vitro release of the blend beads were characterized. The results revealed that the double-crosslinked gel beads had a tightly interpenetrating network structure and exhibited a satisfactory embedding effect for DIN. The maximum of the DIN loading capacity was approximately 1.01%, with a high encapsulation efficiency of 83.19%. The triggered release of DIN from the blend beads was studied in deionized water (pH 3.0-11.0) via high-performance liquid chromatography (HPLC); it was found that the release rate was higher in alkaline pH conditions than in acidic and neutral conditions. An in vivo dynamics and degradation study also demonstrated that the excellent release characteristics of DIN:SA/PVA-beads in the midgut of S. litera. This study provides a promising controlled-release form of dinotefuran that is more effective and can be used for the targeted control of pests with alkaline midgut.

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.

Fabrication of sulfoxaflor-loaded natural polysaccharide floating hydrogel microspheres against Nilaparvata lugens (Stal) in rice fields.

BACKGROUND: Nilaparvata lugens (Stal) nymphs and adults aggregate and feed on leaf sheaths at the base of rice plants. It is difficult to apply traditional spray treatments directly onto the plant stems due to the blocking agent produced by leaves. Further, spiders and mirids, the natural enemies of N. lugens (Stal), are directly exposed to the chemicals during spraying. Sulfoxaflor-loaded natural polysaccharide microspheres with good performance were developed and tested in rice fields. The absorption, distribution, and dissipation of sulfoxaflor in rice plants, soil, and water were examined. RESULTS: Sulfoxaflor-loaded natural polysaccharide microspheres were prepared through physical embedding and ionic crosslinking, using citronellol as an oil phase to provide floatation. The sustained release of sulfoxaflor was achieved through swelling and dissolution, indicating that these structures could effectively control pesticide release. Field experiments showed that these microspheres were able to float in water and gather around the stem of rice plants and that their insecticidal effect was remarkably improved compared to that achieved using the suspension concentrate. Results also showed that the residual content of stems following treatment with sulfoxaflor-loaded natural polysaccharide microspheres reached 0.331 mg kg-1 , but was reduced in other parts of the plant. CONCLUSION: In the present study, sulfoxaflor-loaded natural polysaccharide microspheres with optimized properties were successfully prepared. These microspheres produced a better control effect on N. lugens (Stal) compared to the use of the sulfoxaflor suspension concentrate. Their application may help promote the scientific control of target pests in rice fields. © 2020 Society of Chemical Industry.

Dissipation and distribution of difenoconazole in bananas and a risk assessment of dietary intake.

The dissipation and terminal residues of difenoconazole in whole bananas and pulp were investigated under field conditions. The residual levels of difenoconazole in various parts of bananas grown in Guangdong, Hainan and Yunnan were determined by a GC-ECD detection method after simple, rapid pretreatment. The mean recovery was 80.66~107.40%, and the relative standard deviation was 3.36~9.84%. The results showed that the half-lives of difenoconazole in whole bananas and in the pulp were 12.16~13.33 days and 17.77~20.38 days, respectively. At harvest intervals of 28 and 35 days after the last application, the terminal residues of difenoconazole in whole bananas and pulp were 0.45~0.84 mg/kg and 0.19~0.37 mg/kg, respectively, which were lower than the maximum residue level established in China. The distribution of difenoconazole in banana pulp and peels was studied. The results showed that until harvesting, the residue in the peels was always 2.19~12.30 times larger than that in the pulp. Difenoconazole was mainly absorbed by the banana peels but did not easily penetrate into the pulp. Based on dietary risk assessment results, the residual levels of difenoconazole at the sampling interval of 28 days after the last application were within acceptable limits for chronic and acute dietary risks in different populations in China. This study can provide a reference for the safe and rational use of difenoconazole as a fungicide and for the future research and application of banana pulp and peels.