Dissipation, residues and risk assessment of pyraclostrobin and picoxystrobin in cucumber under field conditions

Status and Perspective on Green Pesticide Utilizations and Food Security

Pesticides protect crops against pests, and green pesticides are referred to as effective, safe, and eco-friendly pesticides that are sustainably synthesized and manufactured (i.e., green chemistry production). Owing to their high efficacy, safety, and ecological compatibility, green pesticides have become a main direction of global pesticide research and development (R&D). Green pesticides attract attention because of their close association with the quality and safety of agricultural produce. In this review, we briefly define green pesticides and outline their significance, current registration, commercialization, and applications in China, the European Union, and the United States. Subsequently, we engage in an in-depth analysis of the impact of newly launched green pesticides on the environment and ecosystems. Finally, we focus on the potential risks of dietary exposure to green pesticides and the possible hazards of chronic toxicity and carcinogenicity. The status of and perspective on green pesticides can hopefully inspire green pesticide R&D and applications to ensure agricultural production and safeguard human and ecological health.

Development of a Time-Resolved Fluorescent Microsphere Test Strip for Rapid, On-Site, and Sensitive Detection of Picoxystrobin in Vegetables

Picoxystrobin (PIC) is a fungicide extensively used for disease control in both crops and vegetables. Residues of PIC in vegetables pose a potential threat to human health due to their accumulation in the food chain. In this study, a specific PIC monoclonal antibody (mAb) was developed by introducing a carboxylic acid arm into PIC and subsequently preparing a hapten and an artificial antigen. A sensitive and rapid time-resolved fluorescence immunochromatographic assay (TRFICA) was established based on the mAb. Subsequently, using a time-resolved fluorescent microsphere (TRFM) as signal probe, mAbs and microspheres were covalently coupled. The activated pH, the mAb diluents, the mAb amount, and the probe amount were optimized. Under optimized conditions, the quantitative limits of detection (qLOD) of PIC in cucumber, green pepper, and tomato using TRFICA were established at 0.61, 0.26, and 3.44 ng/mL, respectively; the 50% inhibiting concentrations (IC50) were 11.76, 5.29, and 37.68 ng/mL, respectively. The linear ranges were 1.81-76.71, 0.80-35.04, and 8.32-170.55 ng/mL, respectively. The average recovery in cucumber, green pepper, and tomato samples ranged from 79.8% to 105.0%, and the corresponding coefficients of variation (CV) were below 14.2%. In addition, 15 vegetable samples were selected and compared with the results obtained using ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS). The results revealed a high degree of concordance between the proposed method and UPLC-MS/MS. In conclusion, the devised TRFICA method is a valuable tool for rapid, on-site, and highly sensitive detection of PIC residues in vegetables.

Dissipation, Residue and Human Dietary Risk Assessment of Pyraclostrobin and Cyazofamid in Grapes Using an HPLC-UV Detector

Pyraclostrobin is a new broad-spectrum methoxyacrylic acid fungicide. Cyazofamid is a new selective foliar spray acaricide. Here, we studied the degradation rate and final residues of pyraclostrobin and cyazofamid in grape and evaluated their dietary risk to consumers. The average recoveries of pyraclostrobin ether ester, cyazofamid and cyazofamid metabolite (CCIM) in grapes were 84-94%, 92-98% and 99-104%, respectively. The relative standard deviations (RSDs) were 6.0-20.3%, 2.4-10.5% and 1.3-4.0%, respectively, and the LOQs were all 0.05 mg/kg. The digestion dynamics of the experimental sites were in accordance with the first-order kinetic equation. The degradation half-lives of pyraclostrobin ether ester and cyazofamid were 17.8 d-28.9 d and 4.3 d-7.8 d, respectively. The final residues of pyraclostrobin ether ester, cyazofamid and CCIM in grapes were <0.05-1.88 mg/kg, <0.05-0.31 mg/kg and <0.05-0.47 mg/kg, respectively. Using probability models, the total chronic risk values for pyraclostrobin and cyazofamid were calculated to be 0.112-189.617% and 0.021-1.714%, respectively. The results of the contribution analysis indicate that pyraclostrobin poses a much greater risk to Chinese consumers than cyazofamid, especially to children and adolescents, who have a significantly greater risk than adults. This suggests that more consideration should be given to the cumulative risk of compounds for vulnerable groups in the future.

Detection Method of Fungal Spores Based on Fingerprint Characteristics of Diffraction-Polarization Images

The most significant aspect of promoting greenhouse productivity is the timely monitoring of disease spores and applying proactive control measures. This paper introduces a method to classify spores of airborne disease in greenhouse crops by using fingerprint characteristics of diffraction-polarized images and machine learning. Initially, a diffraction-polarization imaging system was established, and the diffraction fingerprint images of disease spores were taken in polarization directions of 0°, 45°, 90° and 135°. Subsequently, the diffraction-polarization images were processed, wherein the fingerprint features of the spore diffraction-polarization images were extracted. Finally, a support vector machine (SVM) classification algorithm was used to classify the disease spores. The study's results indicate that the diffraction-polarization imaging system can capture images of disease spores. Different spores all have their own unique diffraction-polarization fingerprint characteristics. The identification rates of tomato gray mold spores, cucumber downy mold spores and cucumber powdery mildew spores were 96.02%, 94.94% and 96.57%, respectively. The average identification rate of spores was 95.85%. This study can provide a research basis for the identification and classification of disease spores.

Terminal Residue and Dietary Risk Assessment of Atrazine and Isoxaflutole in Corn Using High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Isoxaflutole and atrazine are representative pesticides for weed control in corn fields. Formulations containing these two pesticides have been registered in China, and their residues may threaten food safety and human health. In this study, a method for simultaneous determination of isoxaflutole, atrazine, and their metabolites in fresh corn, corn kernels, and corn straw was established based on modified QuEChERS pre-treatment and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The linearity of seven compounds was good (R2 ≥ 0.9912), and the matrix effect was 48.5-77.1%. At four spiked levels of 0.01, 0.02, 0.05, and 0.5 mg kg-1, all compounds' average recovery was 76% to 116%, with relative standard deviation (RSD) less than 18.9%. Field experiments were conducted in Liaoning, Heilongjiang, Inner Mongolia, Shanxi, Beijing, and Yunnan provinces to study the terminal residues. The terminal residues of all compounds were below the LOQ (0.01 mg kg-1) in fresh corn and corn kernels, and atrazine residues in corn straw ranged from <0.05 mg kg-1 to 0.17 mg kg-1. Finally, a dietary risk assessment was conducted based on residues from field trials, food consumption, and acceptable daily intake (ADI). For all populations, the chronic dietary risk probability (RQc) of atrazine was between 0.0185% and 0.0739%, while that of isoxaflutole was 0.0074-0.0296%, much lower than 100%. The results may provide scientific guidance for using isoxaflutole and atrazine in corn field ecosystems.

Residue levels and dietary risk assessment of fluopimomide, pyraclostrobin and its metabolite BF-500-3 in garlic ecosystems under field conditions

To evaluate the residue levels of fluopimomide, pyraclostrobin and its metabolite BF-500-3 in garlic ecosystems, supervised garlic field trials with a commercial formulation (pyraclostrobin·fluopimomide 30% suspension concentrate (SC)) were conducted in six regions of China according to the Good Agricultural Practices (GAP). The residues of fluopimomide, pyraclostrobin and BF-500-3 in field samples were determined using a QuEChERS method combined with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The average recoveries of all target compounds were 76-94% with relative standard deviations (RSDs) of 1.0-14.5% and limits of quantitation (LOQs) of 0.002 mg/kg. At the recommended pre-harvest interval (PHI, 10 days), the residues of fluopimomide, pyraclostrobin and BF-500-3 were below 0.16, 0.77 and 0.12 mg/kg in garlic chive; below 0.027, 0.22 and 0.002 mg/kg in garlic scape; and below 0.002, 0.002 and 0.002 mg/kg in garlic, respectively. Dietary intake risks were calculated using risk quotients (RQs) based on field residual data, toxicological data and dietary patterns. The chronic dietary risk quotients (RQc) of pyraclostrobin and fluopimomide were 48.42% and 0.36%, respectively. The acute dietary risk quotients (RQa) of pyraclostrobin in garlic were 0.06-0.15%. These results indicated a low dietary risk for consumers. This study could provide scientific guidance for the application of pyraclostrobin and fluopimomide in garlic.

Analysis of the fungicidal efficacy, environmental fate, and safety of the application of a mefentrifluconazole and pyraclostrobin mixture to control mango anthracnose

BACKGROUND

Mango anthracnose is among the most severe diseases impacting mango yields and quality. While this disease can be effectively controlled through chemical means, it is vital that appropriate field efficacy and fate determination studies be conducted when applying pesticides to crops in order to appropriately gauge the ecological and health risks associated with the use of these agents.

RESULTS

GAP field trials were conducted to explore the efficacy, dissipation, and terminal residues associated with the application of mefentrifluconazole and pyraclostrobin to mango crops in six locations throughout China. These analyses revealed that three applications of mefentrifluconazole [160 mg active ingredient (a.i.) kg^-1 ] in combination with pyraclostrobin mixture achieved satisfactory disease control efficacy. To simultaneously detect mefentrifluconazole and pyraclostrobin residues on mangoes, a 'quick, easy, cheap, effective, rugged and safe' (QuEChERS) high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS)-based approach was established. The initial mefentrifluconazole and pyraclostrobin concentrations ranged from 0.18 to 0.34 mg kg^-1 , and these two compounds exhibited respective half-lives of 5.6 to 10.8 days and 5.5 to 9.0 days. At 21 days following foliage application, the terminal mefentrifluconazole and pyraclostrobin residue concentrations were 0.02-0.04 and 0.01-0.04 mg kg^-1 , with these concentrations being below the maximum residue limit (MRL) established for pyraclostrobin. Both short-term [acute reference dose percent (ARfD%) 0.78-2.36% and 2.0-6.08%] and chronic [acceptable daily intake percent (ADI%) 0.08-0.47% and 0.09-0.55%] dietary intake risk assessments for mefentrifluconazole and pyraclostrobin indicated that these terminal residue concentrations are acceptable for the general population.

CONCLUSION

Mefentrifluconazole and pyraclostrobin in mango was rapidly degraded following first-order kinetics models. The dietary risk of mefentrifluconazole and pyraclostrobin through mango was negligible to consumers. The application of a 400 g L^-1 mefentrifluconazole-pyraclostrobin suspension concentrate mixture represents a highly efficacious fungicidal approach to controlling mango anthracnose that exhibits significant potential for development as it is easily degraded and associated with low residual concentrations after application. © 2022 Society of Chemical Industry.

Residue Behavior and Risk Assessment of Pyraclostrobin and Thifluzamide in Cowpea

A rapid and sensitive analytical method for determination of pyraclostrobin and thifluzamide in cowpea was established based on QuEChERS sample preparation and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Average recoveries of pyraclostrobin and thifluzamide on cowpea were 100%-105% and 99%-105% with RSDs of 1%-5% and 2%-6%, respectively. The storage stability tests showed degradation rates of < 20% for samples stored at - 18℃ within 12 weeks. The field trials at eight locations in China showed that the residues of pyraclostrobin in cowpea at 3 and 5 days after spraying were 0.081-0.49 mg/kg and 0.029-0.48 mg/kg, and the residues of thifluzamide were 0.12-0.46 mg/kg and 0.047-0.50 mg/kg, respectively, which were all lower than the corresponding maximum residue limits in China. The dissipation of both pyraclostrobin and thifluzamide in cowpea were fast with half-lives (T_1/2) of 1.5-2.3 days and 1.7-2.4 days. This study provided risk assessment data for establishment of good agricultural practice in cowpea plant.

Dissipation and Residues of Pyraclostrobin in Rosa roxburghii and Soil under Filed Conditions

Rosa roxburghii has been widely planted in China. Powdery mildew is the most serious disease of R. roxburghii cultivation. Pyraclostrobin was widely used as a novel fungicide to control powdery mildew of R. roxburghii. To assess the safety of pyraclostrobin for use on R. roxburghii fruits, its residue rapid analysis as well as an investigation on its dissipation behaviors and terminal residues in R. roxburghii and soil under field conditions were carried out. The QuEChERS method was simplified using LC−MS/MS detection and combined with liquid−liquid extraction purification to allow determination of pyraclostrobin levels in R. roxburghii fruits and the soil. The fortified recoveries at 0.1~5.0 mg/kg were 93.48~102.48%, with the relative standard deviation of 0.64~3.21%. The limit of detection of the analytical method was 0.16 and 0.15 µg/kg for R. roxburghii fruit and soil, respectively. The effects of different spray equipment and formulations on the persistence of pyraclostrobin in R.roxburghii were as follows: gaston gasoline piggyback agricultural sprayer (5.38 d) > manual agricultural backpack sprayer (3.37 d) > knapsack multi-function electric sprayer (2.91 d), suspension concentrate (SC) (6.78 d) > wettable powder (WP) (5.64 d) > water dispersible granule (WG) (4.69 d). The degradation of pyraclostrobin followed the first-order kinetics and its half-lives in R.roxburghii and soil were 6.20~7.79 days and 3.86~5.95 days, respectively. The terminal residues of pyraclostrobin in R. roxburghii and soil were 0.169~1.236 mg/kg and 0.105~3.153 mg/kg, respectively. This study provides data for the establishment of the maximum residue limit (MRL) as well as the safe and rational use of pyraclostrobin in R. roxburghii production.

Analysis of dietary exposure and risk assessment of pesticide residues in roots and rhizomes of Chinese herbs

Medicine food homologous (MFH) plants provide therapeutic and health care effects through diet. Thus, a risk assessment system for hazardous ingredient residues is urgently required to ensure their safe use. In this study, the pesticide contamination of six root and rhizome Chinese herbs, Ginseng Radix et Rhizoma, Panacis Quinquefolii Radix, Pseudostellariae Radix, Salviae Miltiorrhizae Radix et Rhizoma, Codonopsis Radix, and Glehniae Radix, and the risks associated with their intake were investigated. A total of 420 MFH plant samples collected from 22 provinces in China were tested, and 61 pesticides were detected in 413 samples. Multiple pesticide residues were detected in each MFH sample, with contents ranging from 0.0002 to 3.010 mg/kg dry weight. Carbendazim (≥47.14%) and propham (≥40%) were the most frequently detected pesticides. Risk assessment determined by hazard quotients indicated that the risks were acceptable, with no short- or long-term adverse health effects. However, considering the high incidence of residues and the detection of unregistered or even prohibited pesticides, strict supervision of soil quality and pesticide application (particularly cadusafos) in MFH plant cultivation are recommended to aid in monitoring MFH plant quality and ensuring diet and drug safety. PRACTICAL APPLICATION: Ensure the diet and drug safety of Chinese herbs.

Chromatographic analysis and residue degradation of phenamacril and difenoconazole on strawberries

Strawberries are widely cultivated and highly consumed globally, but pests and diseases can severely affect yields. Phenamacril and difenoconazole are high-efficacy pesticides and the mixture of these two pesticides offers a satisfactory option for disease control. In this study, an optimised QuEChERS method combined with dispersive solid-phase extraction purification before injection for simultaneously determining the residues of phenamacril-difenoconazole mixture on strawberries was developed and validated using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Average recoveries of phenamacril and difenoconazole in the strawberry matrices ranged from 100% to 104% and 99% to 104%, with relative standard deviations of 2.6%-5.3% and 2.2%-5.5%, respectively. The degradation half-lives of phenamacril and difenoconazole were 3.5-6.6 days and 2.2-3.4 days on strawberries, respectively. Final residues of phenamacril and difenoconazole on strawberries at eight different cultivation regions were 0.033-0.66 mg kg^-1 and <0.02-0.089 mg kg^-1 after spraying at the maximum dosage recommended by the company of 300 mg a.i. kg^-1 twice, respectively. Overall, this study is the first report of phenamacril and difenoconazole residue analysis in strawberries. Therefore, it could provide the reference data for safe management and proper use of phenamacril and difenoconazole in China.

Determination of Pendimethalin Dynamic Residual Distribution in Crucian Carp Tissues and Associated Risk Assessment

Pendimethalin has been considered a moderately to extremely toxic compound for fish and aquatic organism. This study developed the determination of dynamic residual distribution for pendimethalin in crucian carp tissues (muscle, liver, kidney, gill, and blood) under semistatic exposure system by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. The pendimethalin residues in various fish tissues increased initially and then decreased, and the residue amount of pendimethalin varied from tissue to tissue of crucian carp. Particularly, the pendimethalin accumulation in most fish tissues made significant decreases at two-time points. Pendimethalin was initially absorbed and enriched by fish body, and then partial pendimethalin was discharged into the outside environment through the metabolism function of crucian carp. The residue levels of pendimethalin distributed in crucian carp were ranked in the following decreasing order: liver > kidney > gill or muscle > blood, attributed to the fact that pendimethalin tends to accumulate in lipid-rich tissues of fish. Risk assessment results indicated that the chronic risk from dietary exposure to pendimethalin through crucian carp consumption for Chinese residents was acceptable, along with a lower estimated exposure dose (EED) than acceptable daily intake (ADI) and risk quotient (RQ) < 1. This study performed the first analysis for pendimethalin residual distribution in crucian carp tissues under semistatic exposure condition and provided a reference for pollution control and risk assessment of pendimethalin aimed at aquatic products.

Dissipation kinetics and safety evaluation of pyraclostrobin and its desmethoxy metabolite BF 500-3 in a cucumber greenhouse agroecosystem

Pyraclostrobin (PYR), a fungicide of the strobilurin class, is used to control many different kinds of fungal diseases in greenhouses and on agricultural fields. In the present study, an efficient method was established for simultaneously determining PYR and its metabolite BF 500-3 in cucumber fruits, leaves, and soil matrices using QuEChERS pretreatment coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The residue levels and dissipation kinetics of PYR were determined under greenhouse conditions. The recoveries ranged from 89.8 to 103.6% with relative standard deviations (RSDs) of 3.6-7.5% at three spiking levels. The results demonstrated that PYR dissipated quickly in the cucumber field with half-lives (DT₅₀) of 2.14-4.17 days on different sites and in different matrices. The residue of its metabolite BF 500-3 was very low and showed a trend of first increasing and then decreasing. The degradation rate of PYR in soil was the fastest, followed by that on cucumber fruits and leaves. The terminal residue of PYR at an application rate of 150 g a.i. ha^-1 (the maximum recommended rate) in cucumber fruits was below the maximum residue limit (MRL) of 0.5 mg/kg established in China. However, the application of the fungicide at 225 g a.i. ha^-1 (1.5× the maximum recommended rate) resulted in residues that were above the MRL 1 day after the final application, which is an unacceptable risk. Therefore, the application dosage of PYR at the recommended rates was safe to human beings and animals.

The distinct binding modes of pesticides affect the phase transitions of lysozyme

Studying the aggregation and nucleation of proteins in the presence of organic molecules is helpful for disclosing the mechanisms of protein crystallization.