Dissipation behavior, residue distribution and risk assessment of three fungicides in pears

Simultaneous determination of four fungicide residues in figs using liquid chromatography tandem mass spectrometry

Dissipative behavior and final residue levels of difenoconazole, prochloraz, propiconazole, and pyraclostrobin in figs were investigated using field trials and laboratory assays. A three-factor, three-level orthogonal test was designed to optimize the pretreatment conditions of the method. A method was established using high-performance liquid chromatography tandem mass spectrometry for the determination of difenoconazole, prochloraz, propiconazole, and pyraclostrobin residues in figs. The limit of quantification for all four targets in figs was 0.002 mg/kg. Difenoconazole, prochloraz, propiconazole, and pyraclostrobin are readily digestible pesticides in figs with half-lives of 6.4, 6.2, 4.8, and 7.9 days, respectively. Residues of difenoconazole, prochloraz, propiconazole, and pyraclostrobin in figs were below the European Union established residue levels of 0.1, 0.03, 0.01, and 0.02 mg/kg, respectively, at day 7 after application. Pyraclostrobin, propiconazole, difenoconazole, and prochloraz were applied twice at doses of 75, 125, 150, and 200 mg a.i./kg at 7-day intervals, and the residues of the four fungicides in figs were acceptable 7 days after the last application. Therefore, the safety interval can be set at 7 days for 70% difenoconazole-prochloraz wettable powder and 40% pyraclostrobin-propiconazole aqueous emulsion according to the protocol.

Dissipation and Risk Assessment of Propaquizafop in Ginseng under Field Conditions

Propaquizafop is a highly efficient aryloxy phenoxy propionate chiral herbicide. However, the use of propaquizafop, including its safe use methods, residue patterns, dietary risk assessment, and maximum residue limits, for ginseng, a traditional Chinese medicinal plant, has not been studied. An analytical method was established for the simultaneous determination of propaquizafop and its four metabolites in ginseng soil, fresh ginseng, ginseng plant, and dried ginseng using HPLC-MS/MS. This approach showed good linearity (R2 ranging from 0.9827 to 0.9999) and limit of quantification ranging from 0.01 to 0.05 mg/kg. The intra- and interday recovery rates of this method ranged from 71.6 to 107.1% with relative standard deviation ranging from 1.3 to 23.2%. The method was applied to detect residual samples in the field, and it was found that the degradation of propaquizafop in ginseng plants and soil followed a first-order kinetic equation. R2 was between 0.8913 and 0.9666, and the half-life (t1/2) ranged from 5.04 to 8.05 days, indicating that it was an easily degradable pesticide (T1/2 < 30 days). The final propaquizafop residues in ginseng soil, plants, fresh ginseng, and dried ginseng ranged from 0.017 to 0.691 mg/kg. A dietary risk assessment was conducted on the final propaquizafop residue in fresh and dried ginseng. The results showed that the chronic exposure risk quotient values were less than 100% for fresh and dried ginseng (1.15% for fresh ginseng and 1.13% for dried ginseng). This illustrates that the dietary risk associated with the use of 10% propaquizafop emulsifiable concentrate in ginseng is very low. Thus, applying 750 mL/ha of propaquizafop on ginseng could not pose an unacceptable risk to public health. The results of the present study support the registration of propaquizafop in ginseng.

Biocontrol Potential of Streptomyces odonnellii SZF-179 toward Alternaria alternata to Control Pear Black Spot Disease

Pear black spot disease, caused by Alternaria alternata, is a devastating disease in pears and leads to enormous economic losses worldwide. In this investigation, we isolated a Streptomyces odonnellii SZF-179 from the rhizosphere soil of pear plants in China. Indoor confrontation experiments results showed that both SZF-179 and its aseptic filtrate had excellent inhibitory effects against A. alternata. Afterwards, the main antifungal compound of SZF-179 was identified as polyene, with thermal and pH stability in the environment. A microscopic examination of A. alternata mycelium showed severe morphological abnormalities caused by SZF-179. Protective studies showed that SZF-179 fermentation broth could significantly reduce the diameter of the necrotic lesions on pear leaves by 42.25%. Furthermore, the potential of fermentation broth as a foliar treatment to control black leaf spot was also evaluated. Disease indexes of 'Hosui' and 'Wonwhang' pear plants treated with SZF-179 fermentation broth were lower than that of control plants. Overall, SZF-179 is expected to be developed into a safe and broad-spectrum biocontrol agent. No studies to date have evaluated the utility of S. odonnellii for the control of pear black spot disease; our study fills this research gap. Collectively, our findings provide new insights that will aid the control of pear black spot disease, as well as future studies of S. odonnellii strains.

Dissipation and Dietary Risk Assessment of Prochloraz in Strawberries under Greenhouse Conditions

Prochloraz and its metabolites in strawberries have not been determined until now. Meanwhile, few reports in the literature have concerned the dissipation behavior and risk assessment of prochloraz and its metabolites in strawberries under greenhouse conditions in Beijing. A method for the determination of prochloraz and its metabolites in strawberries was developed using QuEChERS in combination with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Prochloraz and its metabolites recovered from strawberries were present in concentrations of 73.06% to 116.01%, their RSDs ranged from 1.12% to 9.17%, and their limits of detection ranged from 0.1 to 1 μg kg-1. Then, a study was conducted on the dissipation of prochloraz in strawberries under greenhouse conditions. The dissipation of prochloraz in strawberries followed the first-order kinetic equation, and its half-life was 8.06 days. The health risk associated with prochloraz in strawberries was evaluated using the target hazard quotient (THQ) method and EFSA PRIMo model. The results showed that the THQ values, %ARfD values, and %ADI values were less than 1. These results indicate that no health concerns of prochloraz are associated with the consumption of the studied strawberries. The government can use the results of this study to support the establishment of a maximum residue level for prochloraz in strawberries.

Eating with peel or not: Investigation of the peel consumption situation and its nutrition, risk analysis, and dietary advice in China

Nutritious, balanced, tasty and easy to eat, fruit is an indispensable health food for consumers. With consumers' increasing respect for the concept of health, green and nutrition, the peel, which has higher nutritional value compared to the pulp, is gradually being emphasized in the consumption process. The suitability of fruit peels for consumption is influenced by various factors, such as the amount of pesticide residues, nutrient content, ease of peeling, and fruit texture, but there is a lack of relevant studies to guide consumers' scientific intake of fruit peels. This review first investigated chineses consumers consumption of common fruits with peels, especially eight fruits that are controversial in terms of whether to consume them with peels, and the results showed that whether people consume peels depends mainly on their nutritional value and pesticide residues. Based on this, the paper discusses the common methods of pesticide detection and removal from fruit peels, as well as the nutrients contained in different fruit peels and their physiological activities, if the peels usually have stronger antioxidant, anti-inflammatory and anti-tumor activities than the pulp. Finally, reasonable dietary recommendations are made on whether fruits should be consumed with their peels, with a view to guiding chineses consumers towards scientific consumption and provide theoretical basis for relevant research in other countries.

The simultaneous degradation of prochloraz and tebuconazole in water with monitoring their degradation products using liquid chromatography-tandem mass spectrometry

Prochloraz and tebuconazole are well-known fungicides for broad applications, including medical, industrial, and agricultural. They are frequently used simultaneously which increases the probability of their co-existing in various water sources. In this study, the analysis of PCZ or TBZ in water was performed by a direct analysis using the liquid chromatography-tandem mass spectrometry technique (LC-MS/MS). The optimized method was fully validated according to the European guidelines, SANTE/11312/2021. The complete degradation of these fungicides (each of 2 mg/L) in their single presence in the water was accomplished just after 15 min using 4.2 mM persulfate at 50 °C, while a lower concentration of persulfate (1.4 mM) leads to a degradation of prochloraz and tebuconazole, in their single existence in water, at percentages of 97 % and 98 %, respectively, after 30 min at 50 °C. On the other hand, it takes a complete hour to degrade a mixture of prochloraz and tebuconazole at percentages of 99 % and 94 %, respectively, using 1.4 mM persulfate at 50 °C. Degradation products (DPds) of prochloraz and tebuconazole, either in their single or simultaneous existing in water, were also identified and monitored during the whole degradation process by LC-MS/MS using at least two mass transitions for each DPd at both positive and negative ionization modes. It was elucidated that the persulfate degradation of prochloraz was conducted by the cleavage of the imidazole ring and the subsequent formation of a trichlorophenol, while persulfate degradation of tebuconazole was mainly accomplished by the formation of a hydroxyl structure, cleavage of the tert-butyl chain, and the subsequent formation of a ketone structure. Furthermore, a new DPd of tebuconazole (m/z = 263 Da) with a diketone structure was identified and confirmed.

A possible but unrecognized risk of acceptable daily intake dose triazole pesticides exposure-bile acid disturbance induced pharmacokinetic changes of oral medication

Triazole antifungal pesticides work by inhibiting the activity of lanosterol-14-α-demethylase, a member of cytochrome P450 enzymes (CYPs), but this effect is non-specific. Bile acids (BAs) are important physical surfactants for lipids absorption in intestine, and synthesized by CYPs 7A1/27A1. Thus, we presume that triazole exposure might influence the therapeutic effect or safety of oral medication through disturbing the BAs pool, even though the exposure is under an acceptable daily intake (ADI) dose. Short- and long-term of ADI dose tebuconazole (TEB) exposure animal models were established through various routes, and statins with different hydrophilic and lipophilic properties were gavaged. It exhibited that the activity of CYP7A1/27A1 was indeed inhibited but the expression was up-regulated, the BAs pool was changed either the content and the composition, and the absorption behavior of statins with strong and medium degree of lipid-solubility were significantly changed. A series of experiments performed on models of intestinal mucus, Caco-2 cell monolayer and Caco-2/HT29 co-culture system revealed that the TEB-exposure induced BAs disturbance made impacts on drug absorption in many aspects, including drug solubility and the structure of intestinal barriers. This study suggests us to be more alert about the hazard of pesticides residues for elderly and chronically ill groups.

Degradation and residues of mandipropamid in soil and ginseng and dietary risk assessment in Chinese culture

Mandipropamid, a new fungicide for oomycete disease, has a strong effect on the blight of many crops and has been registered for the treatment of ginseng blight in China. However, no maximum residue limit (MRL) of mandipropamid has been identified for ginseng, and there have been few related studies. We established and verified the analysis method of mandipropamid in ginseng using high-performance liquid chromatography-tandem mass spectrometry. The method has good linearity and accuracy in the range of 0.002-0.5 mg/kg. The average recovery of mandipropamid was 87.4-101.6%, and the standard deviation was 1.1-4.0. Mandipropamid in ginseng plants and soil rapidly degraded following first-order kinetics models. The degradation dynamics showed that the half-life of mandipropamid in ginseng plant and soil was 13.8-28.0 and 9.8-27.4 d, respectively. After the recommended dose of mandipropamid was applied once, the residual content of mandipropamid in fresh ginseng, dried ginseng, red ginseng, ginseng plant, and ginseng soil was < 0.01-0.185, < 0.01-0.265, 0.085-1.544, 0.075-4.800, and < 0.01-0.014 mg/kg, respectively. The dietary risk assessment of mandipropamid on ginseng showed that the risk quotient value was far less than 100%, indicating that the recommended dose of mandipropamid does not cause unacceptable risks to humans. After the recommended dose of mandipropamid was applied once, it did not cause unacceptable risks to humans. This study not only provides a reasonable spray dosage of mandipropamid to ginseng but also offers a reference for the establishment of MRLs in China.

Peel Diffusion and Antifungal Efficacy of Different Fungicides in Pear Fruit: Structure-Diffusion-Activity Relationships

Fungal pathogens can invade not only the fruit peel but also the outer part of the fruit mesocarp, limiting the efficacy of fungicides. In this study, the relationships between fungicide structure, diffusion capacity and in vivo efficacy were evaluated for the first time. The diffusion capacity from pear peel to mesocarp of 11 antifungal compounds, including p-aminobenzoic acid, carbendazim, difenoconazole, dipicolinic acid, flusilazole, gentamicin, kojic acid, prochloraz, quinolinic acid, thiophanate methyl and thiram was screened. The obtained results indicated that size and especially polarity were negatively correlated with the diffusion capacity. Although some antifungal compounds, such as prochloraz and carbendazim, were completely degraded after a few days in peel and mesocarp, other compounds, such as p-aminobenzoic acid and kojic acid, showed high stability. When applying the antifungal compounds at the EC₅₀ concentrations, it was observed that the compounds with high diffusion capacity showed higher in vivo antifungal activity against Alternaria alternata than compounds with low diffusion capacity. In contrast, there was no relationship between stability and in vivo efficacy. Collectively, the obtained results indicated that the diffusion capacity plays an important role in the efficacy of fungicides for the control of pear fruit diseases.

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.

Dissipation behavior, residue dynamics, and dietary risk assessment of forchlorfenuron in postharvest kiwifruits during simulated cold chain logistics and store shelf life

Forchlorfenuron (CPPU) is often applied during the cultivation of kiwifruit to produce larger fruit. To address degradation patterns of CPPU during simulated cold chain logistics and simulated shelf life of the fruit after harvest, appropriate storage methods and safe consumption behavior can be investigated. In this study, an ultra-high-performance liquid chromatography-tandem mass spectrometry method was adopted to detect CPPU residues under different conditions. CPPU in kiwifruit stored at 6 °C had a half-life of 40.8-77.0 days. However, when kiwifruit was stored at 0 °C under simulated cold chain storage conditions, the half-life of CPPU was 63.0-115.5 days, implying that lower storage temperatures can reduce the degradation rate of CPPU. The residues of CPPU in kiwifruit pulp declined with time, and the reduction followed the first-order kinetics equation. More CPPU residues were present in the pulp of postharvest kiwifruit treated with exogenous ethylene than in the pulp of untreated kiwifruit. Thus, using exogenous ethylene for artificial ripening after harvest is not recommended. We determined that the appropriate cold chain storage temperature is 6 °C. It is recommended that the public select kiwifruit stored for at least 2 weeks. The estimated chronic and acute dietary risk quotients of CPPU are ≤ 0.79% and ≤ 0.11%, respectively. Therefore, it is highly unlikely that consumers will be poisoned by CPPU due to kiwifruit consumption. Our results provide scientific evidence regarding the adoption of appropriate kiwifruit storage methods and consumption behavior to enhance consumption safety.

Study on degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion under field application

BACKGROUND

Propiconazole is widely used to control fungal diseases in field crops, including celery and onion. The potential risk to the environment and human health has aroused much public concern. Therefore, it is significant to investigate the degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion.

RESULTS

A sensitive analytical method for determination of propiconazole residue in celery and onion was established and validated through high-performance liquid chromatography tandem mass spectrometry. The average recovery rate of propiconazole ranged from 85.7% to 101.8%, with a relative standard deviation of 2.1-6.3%. For the dissipation kinetics, the data showed that propiconazole in celery and onion was degraded, with half-lives of 6.1-6.2 days and 8.7-8.8 days respectively. In the terminal residue experiments, the residues of propiconazole were below 4.66 mg kg^-1 in celery after application two or three times and were below 0.029 mg kg^-1 in onion after application of three or four times with an interval of 14 days under the designed dosages. The chronic and acute dietary exposure assessments for propiconazole were valued by risk quotient, with all values being lower than 100%.

CONCLUSION

Propiconazole in celery and onion was rapidly degraded following first-order kinetics models. The dietary risk of propiconazole through celery or onion was negligible to consumers. The study not only offers a valuable reference for reasonable usage of propiconazole on celery and onion, but also facilitates the establishment of maximum residue limits in China. © 2020 Society of Chemical Industry.

Evaluation of Pyraclostrobin as an Ingredient for Soybean Seed Treatment by Analyzing its Accumulation-Dissipation Kinetics, Plant-Growth Activation, and Protection Against Phytophthora sojae

Seed treatment with fungicides has been regarded as a principal, effective, and economic technique for soybean [Glycine max (L.) Merr.] against pathogenic microorganisms during seed germination and seedling growth. Investigation of the characteristics of seed-treatment reagents is an indispensable basis for their application. The aim of the present work is to evaluate the use of pyraclostrobin as an ingredient for soybean seed treatment by investigating its accumulation-dissipation kinetics in plants, plant-growth activation, and protection against Phytophthora sojae. The results showed that the pyraclostrobin stimulated the visible growth (root and shoot length) of soybean plants, increased the chlorophyll level and root activity, and lowered the malonaldehyde (MDA) level. The peak level and bioavailability of pyraclostrobin in soybean roots were 19.9- and 33.2-fold those in leaves, respectively, indicating that pyraclostrobin was mainly accumulated in roots. Pyraclostrobin had a continuous positive effect on the flavonoid levels and the phenylalanine ammonialyase (PAL) activity in roots and leaves, which could enhance the plant defense system. Pyraclostrobin showed in vitro toxicity to P. sojae with a half-inhibition concentration (EC50) of 1.59 and 1.24 μg/mL for pyraclostrobin and pyraclostrobin plus salicylhydroxamic acid (SHAM, an inhibitor of the alternative pathway of respiration), respectively. Seed treatment with pyraclostrobin significantly reduced the severity of Phytophthora root rot, with a control efficacy of 60.7%. To the best of our knowledge, this is the first report on the characteristics of pyraclostrobin used in soybean seed treatment and its efficacy against Phytophthora root rot.