Pre-harvest Interval Research Articles

Silica Nanoparticles as a Probable Anti-Oomycete Compound Against Downy Mildew, and Yield and Quality Enhancer in Grapevines: Field Evaluation, Molecular, Physiological, Ultrastructural, and Toxicity Investigations.

Downy mildew is the most destructive disease of grapevines in the regions of relatively warm and humid climate causing up to 50% yield losses. Application of silicon- (Si-) based products have been extensively studied against various oomycete, fungal, bacterial, and viral plant diseases, but studies on Si application in their nanosize are limited. In this study, the field application of silica nanoparticles (SiNPs) on Thompson Seedless grapevines (H4 strain) infected with downy mildew was evaluated. In addition, molecular, physiological, ultrastructural, and toxicity investigations were also conducted. The obtained results revealed that spraying of grapevines with SiNPs at 150 ppm significantly overexpressed the transcription factor jasmonate and ethylene-responsive factor 3 recording 8.7-fold, and the defense-related genes β-1,3-glucanase (11-fold), peroxidase (10.7-fold) pathogenesis-related-protein 1 (10.6-fold), and chitinase (6.5-fold). Moreover, a reduction up to 81.5% in the disease severity was achieved in response to this treatment. Shoot length and yield per grapevine were considerably enhanced recording up to 26.3 and 23.7% increase, respectively. The berries quality was also improved. Furthermore, this treatment led to an enhancement in the photosynthetic pigments, induction of phenolic and ascorbic acid contents, an increase in the activity of peroxidase and polyphenol oxidase enzymes, and a reduction in the cellular electrolyte leakage, lipid peroxidation, and H2O2 content. Scanning electron microscopy observations showed an increase up to 86.6% in the number of closed stomata and a reduction up to 55% in the average stomatal pore area in response to this treatment. Observations of the transmission electron microscopy showed ultrastructural alterations in the cells of a grapevine leaf due to the infection with downy mildew, including plasmolysis and disruption of the cellular components, abnormal chloroplasts, and thickening of the cell wall and cell membrane. These abnormal alterations were reduced in response to SiNPs spray. In contrast, this study also showed that this treatment had considerable cytotoxic and genotoxic effects at this direct dose/concentration. So, additional investigations to determine the SiNPs residue in the produced edible plant parts are urgently needed. In addition, the pre-harvest interval, toxicity index, and risk assessment should be evaluated before any recommendation for use.

Degradation of the insecticides fipronil and cypermethrin in green onions (Allium fistulosum) and mustard greens (Brassica juncea)

Pesticide dissipation on foods like vegetables, fruits, and cereals is one of the most concerning aspects in pesticide toxicology as it involves risks to human health and food safety. In light if this, a laboratory-scale study was conducted for two separate systems, green onions (Allium fistulosum) and mustard greens (Brassica juncea),in order to identify the dissipation of fipronil and cypermethrin, two commonly used insecticides, under a tropical climate. After the pesticide application, vegetable samples from these microcosms were collected each day for 7 days to measure fipronil and cypermethrin (n=3) residues. The analytical method was validated and showed repeatability and trueness. The decay equations fit well to first-order kinetics with a correlation coefficient of R2>0.93 and p<0.0005. The calculated half-life values of fipronil were 2.9 d for green onions and 3.2 d for mustard greens while those of cypermethrin were, respectively, 4.5 d and 3.2 d. To meet the maximum residue levels (MRL) of fipronil (0.02 mg/kg) and cypermethrin (0.7 mg/kg) on vegetables, the estimated pre-harvest intervals should be updated to 23 d and 7.5 d, respectively.

Bioefficacy, residue dynamics and dietary risk assessment of gibberellic acid in improving the potential yield of tomato (Solanum lycopersicum L.).

The increasing use of gibberellic acid (GA3) to promote fruit growth and yield has necessitated research into its trace level determination and estimation in harvested product. The phytohormone has increased the tomato yield (tonne ha-1) up to 24.7% with uniform fruit shape, size colour and lustre. A fast, simple, high-throughput analytical method was standardised based on electrospray ionisation - liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted using acidified (1% formic acid) methanol. The method was validated as per the SANTE/12682/2019 guidelines. The limits of detection (LOD) and quantification (LOQ) were 0.01 and 0.05mgkg-1. The average recoveries at LOQ and higher levels were in the range of 86-108% with relative standard deviation (RSD) < 20%. The validated method was successfully applied under field condition by following first-order kinetics with half-lives (T1/2) 1.76days (recommended dose) and 1.99days (double dose). The estimated pre-harvest intervals (PHIs) were 6days (recommended dose) and 8days (double dose). Studies on dietary risk assessment concluded that even after spray of GA3 at recommended dose, the harvested produce (tomato) could be consumed safely.

Dissipation and residue of fosthiazate in tomato and cherry tomato and a risk assessment of dietary intake.

In this study, the safety and risk of fosthiazate as a nematicide against root-knot nematode in tomato and cherry tomato were evaluated. The dissipation and residue of fosthiazate for 28 days in tomatoes and cherry tomatoes were determined and studied by HPLC after simple, rapid pre-treatment. The mean recovery was 83.79~94.18%, and the relative standard deviations were 3.97~7.40%. Results showed that the half-lives of fosthiazate in tomatoes (4.81~5.37 days) were significantly lower than that in cherry tomatoes (5.25~5.73 days). At the pre-harvest interval (PHI) of 21 days, the residues of tomatoes and cherry tomatoes were 0.032~0.046 mg/kg, which were lower than the maximum residue level (MRL) established in China. The potential risks of fosthiazate exposure through the dietary intake of tomatoes and cherry tomatoes to different populations were also studied. According to the results of dietary risk assessment, the residual levels of fosthiazate were within the acceptable range of long-term dietary risk in different populations in China within the sampling interval of 21 days after the application of fosthiazate. Our results show that fosthiazate at 2250 g.a.i./ha in the field control of root-knot nematode has high safety and low risk, and can provide a reference for the safe and reasonable use of fosthiazate as a nematicide in the field.

Residue and distribution of fosthiazate in cucumber (Cucumis sativus L.) and dietary intake risk assessment for various populations

ABSTRACT The safety and risk of fosthiazate as nematicide in cucumber field were evaluated in this study. An analytical method for determining the residues of fosthiazate in cucumber was developed. Mean recoveries and relative standard deviations in all samples ranged 85.3 ~ 95.0% and 5.7 ~ 13.3%. The half-lives of fosthiazate in cucumber root, leaf and fruit were 4.71 ~ 5.50 days, 3.52 ~ 4.78 days and 3.32 ~ 3.96 days. The residues in cucumber fruits were below the maximum residue limit (MRL) in China, based on the application dose of 900 g a.i./ha and the pre-harvest interval of 14 days. The transfer rates of fosthiazate from cucumber root to leaf were 17.48 ~ 46.03%, which were significantly higher than those of root to fruit (8.81 ~ 26.52%). These results indicated that fosthiazate was mainly distributed in cucumber root, and it was difficult to be absorbed by the fruit compared to the leaf. The long-term dietary intake risk assessment results showed that the risk quotient (RQ) ranged 20.04 ~ 36.25% and were less than 100%, which indicated that fosthiazate has a low risk for long-term dietary intake of cucumbers. Overall, our results would be considered as important references for safe and reasonable use of fosthiazate, monitoring and assessing the food safety, and protecting consumer health.

Assessment of management practices, awareness on safe use of pesticides and perception on integrated management of pests and diseases of chilli and tomato grown by small-scale farmers in selected districts of Sri Lanka.

In this study, we surveyed through a structured and pilot-tested questionnaire, the practices of pesticide usage by small-scale (< 1.25 ha) chilli and tomato farmers from four districts of Sri Lanka and their perceptions on the effectiveness of pesticides and willingness to adopt integrated pest management (IPM). We found significant (P < 0.05) variation among districts in farmer responses to 37 out of 59 survey questions. A majority of farmers were dependent on pesticides with only a minority practicing IPM. A majority perceived that their current pesticide usage was increasing, but was not excessive. A majority were aware of the negative impacts of pesticides on human health and environment. Farmer perception on the effectiveness of pesticides increased with age, but was not influenced by education level. Farmers having a higher opinion of pesticides made a greater number of applications during a cropping cycle. They also maintained a longer preharvest interval and did not use pesticide mixtures. A majority expressed willingness to initiate IPM, but identified lack of knowledge and technical knowhow on specific IPM practices for their crops as barriers to adoption and requested external support. Farmer willingness to adopt IPM is higher among older, more educated farmers and among full-time farmers who are currently totally-dependent on pesticides and whose major income source was farming. We conclude that a significant extension effort in terms of farmer education on IPM and external assistance to develop the technological knowhow, which is tailor-made to specific districts, is needed to facilitate adoption of IPM among these farmers.

Appraisal for Edible Use of Vegetable Crops Cultivated in Egypt after Treatment with Selected Insecticides and Fungicides: Insights of Dissipation Rates and Pre-harvest Intervals.

An analytical investigation was carried out to study the dissipation rate of two commonly used pesticides, thiamethoxam (neonicotinoid insecticide) and propamocarb hydrochloride (carbamate fungicide), applied to four vegetable crops: cucumber, zucchini, lettuce and pepper, after open-field application. Samples were harvested according to a scheduled plan followed by QuEChERS extraction, then thiamethoxam residues were analyzed using a GC-ECD method, while propamocarb HCl residues were analyzed using an HPLC-UV method. Validation parameters were attained for both methods and the kinetic profile was studied, which fitted the first-order kinetics where k, t1/2 and t90 were calculated. The proper pre-harvest interval (PHI) was studied for each crop to ensure that the residues levels declined to reach below the maximum residue limit (MRL) where the crop is suitable for consumption. These values were found to be different from labelled values, which proves that the PHIs are greatly affected by changing weather conditions.

Dissipation, occurrence, and risk assessment of 12 pesticides in Dendrobium officinale Kimura et Migo

The residual behaviors and dietary risk probability of 12 pesticides in Dendrobium officinale Kimura et Migo cultivated at two representative locations under green house conditions were investigated using liquid chromatography-tandem mass spectrometry. Field trials showed that the half-lives of 12 pesticides ranged from 0.9 to 14.4 days in fresh D. officinale stems. Based on maximum residue levels (MRLs), the ultimate residues of imidacloprid, dimethomorph, metalaxyl, tebuconazole, and cyazofamid at a pre-harvest interval (PHI) of 28 days were within acceptable limits. For abamectin, indoxacarb, and difenoconazole, 35-day PHIs were needed. The PHIs of trifloxystrobin and fluopyram were 42 days, the time required for their residues to be reduced to an MRL of 4 mg/kg. The chronic and acute risk quotients of target pesticides at PHIs of 28–42 days were below 5.929% and 0.532%, respectively, showing that the evaluated D. officinale exhibited an acceptably low dietary risk to the general population.

The Residual Behavior of Chlorothalonil and Metalaxyl in The Egyptian Cucumbers Fields Infested with Downy Mildew Using The High-Performance Liquid Chromatography (Hplc) and Quechers Method. سلوک متبقيات الکلوروثالونيل والميتالاکسيل فى حقول الخيار المصابه بالبياض الزغبى بإستخدام جهاز الکروماتوجراف السائل عالى الأداء HPLC)) بإستخدام طريقة الـQUECHER.

The dissipation rate of the commercial fungicide with two active ingredients (Chlorothalonil 64% + Metalaxyl 8%) that was approved by the agriculture pesticides committee was evaluated in the cucumber fields infested with downy mildew in Egypt using HPLC analytical system. The experiment was designed in randomized block design. After spraying at the recommended rate of applications, the samples of cucumber were chosen randomly from treated and un-treated plants after the interval of zero time(2hours), 1, 3, 7,10, and 14 days. The technique was validated at different fortification levels (0.01, 0.5, and 0.1 μg mL−1). The recoveries of both fungicides Chlorothalonil and Metalaxyl were 87.6 and 95 %. The results showed that the initial residues (zero time) were 4.38and 3.21 mg/kg-1. All detected residues significantly decreased upon time elevated. The residues extracted by an optimized QuEChERS coupled with HPLC analytical system were accurate and acceptable The limit of quantitation was 0.05 for both fungicides. The dissipation curves of both Chlorothalonil and Metalaxyl followed the first-order kinetics. The half-life’s (t½) values were 0.89 and 1.1days in, respectively. Under the optimized condition, the residues of Chlorothalonil and Metalaxyl in cucumber were below the codex maximum residue limit (0.5 and 3 mg/kg-1). Consequently, the pre-harvest intervals (PHI) in cucumber were seven days for the fungicide.

Residue level and health risk assessment of organophosphorus pesticides in eggplant and cauliflower collected from Dhaka city, Bangladesh

Residue levels of seven organophosphorus pesticides in two vegetables (eggplant and cauliflower) collected from major markets of Dhaka city, Bangladesh were analysed. The collected samples were analysed using a modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction technique by Gas Chromatography coupled with Flame Thermionic Detector (GC-FTD). Among the 50 analysed samples of the eggplant 12% samples contained residues of chlorpyrifos (0.384~0.980 mg/kg), 6% samples contained residue of dimethoate (0.052~0.132 mg/kg) and 2% samples contained residue of diazinon (0.01 mg/kg). Whereas, among the 50 samples of cauliflower, 12% samples contained residues of chlorpyrifos (0.056~0.540 mg/kg), 8% samples contained residues of diazinon (0.033~0.42 mg/kg) and 2% samples contained residues of quinalphos (0.06 mg/kg). The chlorpyrifos was found as the most frequently detected organophosphorus pesticide. Among the 21 contaminated samples, 20 were above EU-MRL. Short and long-term health risk assessment based on ARfD and ADI indicates that the intake risks of eggplant and cauliflower were in the acceptable range. Nevertheless, establishing strong monitoring and traceability system together with controlling pre-harvest interval needed to ensure food safety, consumer confidence and promote vegetable export from Bangladesh.

DISSIPATION OF CYFLUMETOFEN IN STRAWBERRY FRUITS AND GREEN BEAN PODS UNDER GREENHOUSE CONDITIONS USING QUECHERS METHOD AND GC/(μ-ECD)

Strawberry and green bean are important cash crops. Both are highly infected by different pests under greenhouse conditions causing reduction in quality and yield. Mites are usually from the most common pests of beans and strawberries. Field experiment was carried out to investigate dissipation of Cyflumetofen (a novel acaricide) in strawberry fruits and green bean pods. Determination was done using quick, easy, cheap, effective, rugged, safe (QuEChERS) method and cleanup step utilizing dispersive solid-phase extraction (DSPE) followed by gas chromatography coupled with a micro electron capture detector GC/(μ-ECD). Average recoveries were within 80.75-92.15% and 80.86-82.91%, with relative standard deviations (RSDs) ranging from 2.8 to 6.6% and 3.59-4.70%. in strawberry and green bean samples, respectively at spiking levels (0.01 - 1 mg/kg). Linearity was achieved for Cyflumetofen with correlation coefficient R2 > 0.98 and matrix-matched calibration also showed linearity with determination coefficients R2 > 0.98. The initial deposits in strawberry fruits and green bean pods were 2.48 and 3.24 mg/kg, respectively. The half-life period (RL50) in strawberry fruits and green bean pods was 1.81 and 1.16 days, respectively. According to maximum residue level (MRL) which is 0.6 mg/kg, the pre-harvest interval (PHI) was estimated to be 3 days in strawberry fruits.

Determination of fungicides' residues and their degradation kinetics in orange tree fruits using liquid chromatography – Tandem mass spectrometry coupled with QuEChERS method

A new, sensitive, selective and validated LC-MS/MS method has been developed for the determination of five fungicides namely; Carbendazim, Thiabendazole, Metalaxyl, Imazalil and Propiconazole in orange samples. Sample pretreatment was performed using the QuEChERS technique where orange samples were extracted using acetonitrile and were centrifuged for 5 min. Procedural standard calibration was applied to compensate for signal suppression due to the matrix effect. LC-MS/MS parameters were optimized to quantify the least concentration of the studied fungicides below maximum residue limits. Isocratic elution using 10 mM ammonium formate buffer pH 4 (10%), and methanol (90%) on Agilent C18 column ZORBAX Eclipse plus was applied with total elution time of 5 min. Trueness results, according to SANTE guideline, ranged from 101.04% to 104.51% with average %RSD < 7.01%, The method detection limit and limit of quantification were in the range of (0.67–1.25 ng/g) and (2.24–4.15 ng/g) respectively. The proposed method was successfully used to quantify the residuals amounts of the selected fungicides in different market and organic orange samples. It is the first time to study the degradation kinetics of these fungicides in citrus fruits, as well as their half-lives and their predicted preharvest interval, in the real orange samples from orange trees after their treatment with the studied fungicides.

Dissipation behaviour and risk assessment of fipronil and its metabolites in paddy ecosystem using GC-ECD and confirmation by GC-MS/MS

Fipronil -a broad spectrum phenylpyrazole insecticide has high level of toxicity towards environment. Therefore, an easy and reliable analytical method was developed for residue estimation of fipronil to ensure food and environmental safety. A modified QuEChERS technique was followed for estimation of fipronil (5% SC) in paddy ecosystem using GC-ECD and confirmation by GC-MS/MS. The initial residues (0.168–0.794 μg g−1) of total fipronil i.e., sum of fipronil and its metabolites (viz., desulfinyl and sulfone) in leaf and soil were dissipated following first order kinetics. About 92–96% of fipronil residues were degraded after 15 days with half-life of 3.4–4.1 days and pre-harvest interval of 19.4–25.7 days in plant. Residues were below level of quantification (<0.005 μg g−1) in plant and soil at harvest. The fipronil residues in rice grain present low dietary risk (RQd < 1) to human health. However, high risk (RQd > 1) was predicted for cattle health due to fipronil residues in paddy leaf up to 10 days. The residual level in soil was also at highrisk (RQs > 1) for soil ecological health.

Effect of Vegetable Commercialization on Food Safety

The commercialization of fresh vegetables is crucial in enhancing revenues from commercial vegetable farming and ensuring reliable supply of high-quality produce for consumers. However, this is only guaranteed under ethical application of agrochemicals beyond which can lead in a more pronounced public health as well as environmental hazards. The present paper sought to examine the influence of commercialization on food safety. Vegetable samples weighing between 1 to 2 kg were purchased from randomly selected producers in two major producing counties (Kiambu and Kirinyaga) in Kenya. All samples were freeze-dried and stored in an ice chess box, to minimize contamination. Then the samples were labeled, and transported to the laboratory for processing and testing. All approved samples were subjected to the QuEChERS preparation method for pesticides and quantified using gas chromatography equipped with mass spectrometry (GC-MS). Lab results tested positive for 13 problematic pesticides including known carcinogens and highly hazardous agrochemicals such as Malathion, chlorothalonil and chlorpyrifos. The most common agrochemical was carbofuran (67%) in terms of insecticide. For the case of fungicides, the most common was mancozeb (60%) and metalaxyl (58%). Food safety issues are caused mainly by not observing preharvest intervals, excessive application of chemicals and use of illegal agrochemicals. Chemical residues in food mainly results in carcinogenic diseases (43 to 49%), stomach related problems (15 to 19%), eye related problems (10 to 15%), and skin related problems (11 to 14%) and breathing difficulties (10 to 12%). This study demonstrates that there is a problem of agrochemical use and food safety concerns and kale and tomato value chain.

Changes in pesticide residues in field-treated fresh grapes during raisin production by different methods of drying

Drying is one of the best food preservation methods, especially for grapes. This study aimed to determine the fate of pesticides after grapes are being subjected to different drying methods, namely, sun-, oven-, shade-, and alkaline-drying, which are employed in raisin production. Pesticide residues were determined by gas chromatography–tandem mass spectrometry (GC–MS/MS). Washing before drying decreased the diazinon, ethion, phosalone, penconazole, and hexaconazole levels in the grape samples by 52.04%, 6.75%, 9.99%, 56.54%, and 20.97%, respectively. In the raisins, the concentration of all the pesticide residues increased based on wet weight, and this result was due to dehydration; by contrast, the concentrations of the pesticides decreased based on dry weight. The sun-drying method demonstrated the greatest efficiency in residue removal wherein it decreased the diazinon, ethion, phosalone, penconazole, and hexaconazole levels by 76.65%, 68.40%, 69.55%, 72.74%, and 82.19% (dry weight), respectively. On the contrary, the shade-drying method demonstrated the least efficiency in reducing the residue levels (19.57%–42.55%). The evaluation of the processing results showed pesticide residue level in the raisins prepared using the investigated drying methods was higher than the maximum residual limits (MRL). This finding indicates that it is necessary to consider the pre-harvest interval in pesticide application in grape.

Levels of residues and dietary risk assessment of the fungicides myclobutanil, penconazole, tebuconazole, and triadimenol in squash.

Triazole fungicides may potentially harm human health. The 'quick, easy, cheap, effective, rugged, and safe' approach has become popular for extraction and cleanup during pesticide residue analysis. We aimed to (a) validate a method for the simultaneous determination of myclobutanil, penconazole, tebuconazole, and triadimenol in squash using LC-MS/MS and (b) determine the pre-harvest intervals (PHIs) and assess the related risk of consuming squash cultivated under open-field conditions in Saudi Arabia. Using acetonitrile as the extraction solvent and fourfold dilution in deionized water led to weak signal suppression (<-6.1%). The limits of quantitation ranged from 10 to 40 μg/kg. Mean recovery and relative standard deviation ranged from 81.7 to 96.3% and from 3.6 to 11.4%. The half-lives ranged from 2.22 to 3.83 days, and the dissipation followed first-order kinetics. The terminal residues of myclobutanil, penconazole, tebuconazole, and triadimenol were <0.771, <0.307, <0.459, and <0.954 mg/kg, respectively, 7days after two or three applications of recommended dosages. The PHIs of 7.1-11.4, 8.7-13.1, 3.8-5.3, and 11.3-14.3days are suggested after the application of the recommended dose and double the recommended dose. A consumer risk assessment based on estimated dietary intake indicated that the consumption of squash treated with the recommended doses does not pose a significant health risk.

Distribution of fluopyram and tebuconazole in pomegranate tissues and their risk assessment

Residue distribution of fluopyram and tebuconazole was assessed in pomegranate whole fruit, aril, outer peel (pericarp), inner peel (mesocarp) and leaves. The method LOQ of fluopyram and tebuconazole were 0.01 and 0.02 mg kg−1, respectively. Both fungicides remained in fruit peel and residues in edible aril were < LOQ. In fruit peel major portion of the fungicides remained on pericarp with minimal movement to mesocarp. In mesocarp fluopyram was 5.7–14.2%; tebuconazole, 7.5–14.4% of the residues in pericarp. Terminal residues of fluopyram and tebuconazole in pomegranate whole fruit were 0.037–0.094 and 0.036–0.096 mg kg−1. Half-life of fluopyram in pomegranate fruit and leaves were 7.3–9.1 and 15 days; tebuconazole, 8–10.3 and 11.2–12.6 days, respectively. Pre-harvest intervals for treatment of combination formulation of fluopyram and tebuconazole, were 47–59 days in fruits, 158–173 in leaves. Dietary risk assessment demonstrated that consumption of peel and leaves may pose risk to human health, whereas fruit consumption was considered safe.

Dissipation kinetics and processing behavior of boscalid and pyraclostrobin in greenhouse dill plant (Anethum graveolens L.) and soil

Determining the environmental behavior and fate of chemical compounds during technological processing of plants is a task of great significance nowadays. However, the current knowledge is still incomplete for unique herbal matrices belonging to minor crops. The research in this article presents, for the first time, the dissipation kinetics and processing behavior of carboxamide boscalid (BOS) and stobilurin pyraclostrobin (PYR) fungicides during glasshouse dill (Anethum graveolens L.) cultivation. The half-lives (t1/2 ) of BOS and PYR after application at the recommended and double dosage were in the range: 1.62-2.01 days in plant and 2.08-4.85 days in soil, respectively. The processing behavior in dill was estimated after washing, hot air drying and drying in sunlight without/with pretreatment. Processing factors (PFs) were above 1 after drying (PF=1.24-1.39 hot air; PF=1.15-1.28 sunlight) and below this value when the washing step was applied (PF=0.31-0.42 hot air; PF=0.21-0.34 sunlight), indicating the highest effectiveness of reduction, up to 73% BOS and 79% PYR. BOS/PYR residues at pre-harvest intervals after both doses were below European Union (EU) maximum residue limits (MRLs). The highest effectiveness was noted for drying carried out with the washing step, which has a great influence on the concentration of residues in the final product. The findings can supplement PF databases not set for minor crops and can be used to establish MRLs and determine human exposures more accurately in risk assessment studies. © 2021 Society of Chemical Industry.

Residual behavior and dietary intake risk assessment of flonicamid, dinotefuran and its metabolites on peach trees.

Flonicamid and dinotefuran are widely applied to control pests and diseases in various economic crops arousing much public concerns about the potential risk to human health. In this study, the multi-determination and residual behavior of flonicamid-dinotefuran mixture on peach trees were investigated. The chronic risk of long-term dietary intake for Chinese consumers was evaluated. An optimized QuEChERS method combined with ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis for simultaneous determination of flonicamid, dinotefuran and its metabolites was established to analyze the residual dissipation and terminal residues in peach matrices. The results demonstrated that (i) a satisfactory linearity relationship with the detector response and the correlation coefficient R2 > 0.999, the average recoveries of these four analytes ranged from 94 to 108%, the relative standard deviation was between 1.0% and 8.8%, and the limit of the quantitation was 0.02 mg kg-1 ; (ii) the dissipation behaviors of flonicamid and dinotefuran followed with the first-order dynamic kinetics model, and the half-lives were 6.9-12.4 days and 8.1-15.1 days, respectively; (iii) the recommended preharvest interval (PHI) was 21 days, the risk quotient (RQ) values of flonicamid and dinotefuran were 16.6 and 20.7%, respectively, which were significantly less than 100%. The established analytical method met the detection requirement in terms of sensitivity, accuracy, and precision. Additionally, the results indicated that the potential dietary intake risk of the flonicamid-dinotefuran mixture on peach trees was negligible. This work can be utilized in the safe and responsible use of flonicamid-dinotefuran mixture and provide guidance for establishing its maximum residue limit (MRL) in China. © 2021 Society of Chemical Industry.

Assessment of pesticide residues level in watermelon fruits [Citrullus lanatus (Thunberg) Matsumura and Nakai] in Lower, Central and Upper Badibou Districts in North Bank Region, of the Gambia

Field and laboratory studies were conducted late 2019 in three districts of the Gambia’s North Bank Region; namely, Central Badibou, Lower Badibou and Upper Badibou to ascertain the pesticide residue level in watermelon fruit, determine the insect pest control methods, types of pesticide, frequency of application, and pre-harvest interval observed. Multistage sampling technique was used in selecting the research respondents. Eighty-five (85) farmers were identified; forty-five (45) were randomly selected as research respondents. Data was collected using structured questionnaires. SPSS Software was used to analyse the questionnaires and Gas Chromatograph to determine the pesticide residue level. Data obtained were analysed and compared with the European Union Maximum Residue Limit (MRL). The results of the analysis revealed that the farmers used chemical control method in watermelon production, and applied at frequency of once in every two weeks. Furthermore, the results indicated that the chemical applied at flowering stage and the pre-harvest interval (17-21 days) ranked the highest. The pesticides residues found in the watermelon samples were Dimethoate, Profenophos, Dicofol, Cypermethrin, Lambda-cyhalothrin, Permethrin and Deltamethrin and most were above the MRL. The presence of pesticides residues in the watermelon samples calls for strict regulation on the use of pesticides on watermelon. Further study is recommended in other fruits and vegetables grown in the country especially in the studied region.