Dissipation kinetics and risk assessment of iprovalicarb + propineb fungicide in tomato under different agroclimates

Analysis, residue behaviour and risk assessment of combination product of iprovalicarb + copper oxychloride in representative fruiting vegetables, cucurbit and in soil using LC-MS/MS and ICP-MS

Combination product of two herbicides, i.e. iprovalicarb and copper oxychloride, is a new formulation. There is paucity of data on the dissipation pattern and risk assessment of this combination product in crops. To understand the dissipation behaviour/kinetics of this product, a supervised field trial was undertaken on cucumber and tomato. Method validation for a QuEChERS-based method for analysis of these pesticides from cucumber and tomato matrices reveals that all the parameters were within the acceptance range in accordance with SANTE. The limit of quantitation (LOQ) for iprovalicarb in cucumber and tomato fruits, and in soil matrices when analysed on LC-MS/MS was established at 0.01 mg kg-1. Similarly, the LOQ for copper oxychloride (as copper) on ICP-MS was established at 0.5 mg kg-1 in cucumber and tomato fruits and 5.0 mg kg-1 in soil. Dissipation of iprovalicarb was slower in tomato fruits as compared to cucumber fruits. The initial accumulation of the residues of iprovalicarb was 0.073 and 0.243 mg kg-1 in cucumber and 0.214 and 0.432 mg kg-1 in tomato fruits at standard and double dose, respectively. Similarly, copper oxychloride residues were 3.51 and 6.45 mg kg-1 in cucumber and 1.26 and 2.56 mg kg-1 in tomato fruits at standard and double dose, respectively. The residues were below LOQ in cucumber fruits, tomato fruits and soil at the time of harvest. The residues of copper oxychloride persisted till harvest time in cucumber fruits and in soil. A preharvest interval (PHI) of 3 day is recommended on safer side for the combination product of iprovalicarb + copper oxychloride. Theoretical maximum daily intake (TMDI) is less than maximum permissible intake (MPI) for iprovalicarb and copper oxychloride at both the doses from 0 day and onward. The results from the present study can be of immense importance for establishing label claims, maximum residue limits (MRLs) and risk assessment by national and international regulatory agencies.

Systemic enantioselectivity study of penthiopyrad: enantioselective bioactivity, acute toxicity, degradation and influence on tomato

BACKGROUND

In order to promote the green development of agriculture, it is important to study the enantioselective effect of chiral pesticides. The bioactivity of the chiral fungicide penthiopyrad (PEN) racemate and enantiomers against phytopathogens, toxicity to non-target organisms, effect on tomato fruit growth and maturation, and environmental fate in tomato cultivation were evaluated at an enantioselective level in this study.

RESULTS

The results indicated that at the same efficacy, the optically pure S-(+)-PEN could lower the dosage of racemate by 20-96%. The S-enantiomer had low toxicity to earthworms. Besides, the S-(+)-PEN did not cause significant abiotic stress to the tomato and increased fruit fresh weight and size via modulating the contents of plant hormones. However, the content of hydrogen peroxide (H₂ O₂ ), superoxide (O₂ ^- ) and malondialdehyde in the R-enantiomer treatment group was significantly higher than the control group. The effect of the racemate on tomato fruit was between the enantiomers. Furthermore, compared to R-(-)-PEN and racemate, the S-enantiomer degraded more quickly in tomato fruit, leaves, and soil, reducing the danger of human exposure.

CONCLUSION

The S-enantiomer is highly effective and less toxic. The development of enantiomer pure S-(+)-PEN products might be an efficient and low-risk strategy. The results lay the foundation for comprehensive evaluation and proper application of PEN. © 2023 Society of Chemical Industry.

Simultaneous monitoring and dietary risk assessment of 386 pesticides in market samples of black tea

Black tea samples (390) collected from local markets situated in different locations of India were monitored for the residues of 386 pesticides using QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) based extraction and analysis by gas and liquid chromatography tandem mass spectrometry (GC-MS/MS and LC-MS/MS). Residues of seventeen pesticides were detected, of which propargite, cypermethrin, and novaluron showed the highest % positive detections. A comparison of the concentrations of the detected pesticide residues with the available national and international maximum residue limits (MRLs) showed that seven samples exceeded the Indian MRLs while no sample was found to exceed the CODEX MRLs. The risk due to the detected pesticide levels evaluated in terms of hazard quotient (HQ) and hazard index (HI) was found to be very low (<1), suggesting that the pesticide residues in the tea were safe for consumption by Indian adults and children.

Foliar application of three dithiocarbamates inhibits the absorption and accumulation of Cd in wheat

In cadmium (Cd) contaminated farmland soil, antagonism between elements can be used to control the absorption and accumulation of Cd in crops through the external application of zinc (Zn) and manganese (Mn). Dithiocarbamates (DTCs) are highly effective fungicides commonly used in farmlands, and DTCs are rich in Zn and Mn. We selected three representative DTCs (propineb, mancozeb, and zineb) for a field experiment in Henan province, China. The effects of DTC on Cd absorption and accumulation in wheat and the interaction of Zn, Mn, and Cd in wheat after spraying of DTC were studied using different application times at the heading stage. The results showed that after foliar spraying of DTCs according to pesticide application requirements, wheat yield was not affected. The Zn and Mn contents in grains increased, with the highest increases being 19.2% and 12.4%, respectively. Zn and Cd as well as Mn and Cd were antagonistic in wheat, and the transport of Cd from soil to root and from husk to grain was inhibited. The bioconcentration factor (grains/soil) decreased from 1.3 to 0.68 and the translocation factor (grains/husks) decreased from 0.76 to 0.35. The Cd content in grains decreased by 60.4%, 52.8%, and 25.6% with mancozeb, propineb, and zineb applications, respectively, and the Cd reduction effect of spraying DTCs twice was better than that of spraying DTCs once and thrice. The results show that DTCs application could reduce the Cd content in wheat grains and realize the dual effects of crop disease prevention and Cd reduction.

Farm to table: Residues of different pesticides in tomato and tomato juice - Food safety aspects

During plant cultivation, the pesticides can get into the tissue of vegetables due to crop protection processes, and thus into the food chain. Therefore, they constitute a potential risk to the consumer's health. Depletion of pesticides [spirotetramat (Movento), azoxystrobin and difenoconazole (Amistar Top)] was monitored by testing tomatoes treated individually or simultaneously and tomato juices prepared from the treated tomatoes. The investigations aimed to reveal any kinetic interaction between the compounds tested and changes in their elimination, and thus to assess their compliance with the official Maximum Residue Limits (MRLs). The co-presence of pesticides prolonged the elimination of the individual compounds which reached significantly higher residue levels (P < 0.0001) in tomato, especially difenoconazole (45%) and azoxystrobin (50%) on day 8 after treatment that can cause food safety issues to the human consumers. However, the concentrations of pesticides applied alone or simultaneously were found to be below the corresponding MRL values after the withdrawal period in all investigated tomato and tomato juice samples. Accordingly, the investigated pesticides can be safely used simultaneously, their concentrations are in compliance with the legal regulations and thus their concomitant presence does not pose any risk to the consumers' health.

Dissipation kinetics, safety evaluation, and decontamination of residues of the combo-formulation iprovalicarb 8.4% + copper oxychloride 40.6% WG in/on grapes (Vitis vinifera L.)

A field experiment was conducted to study the dissipation behavior and decontamination of iprovalicarb and copper oxychloride in grapes. After thorough validation, the analysis was carried out by employing LC-MS/MS for iprovalicarb and AAS for copper oxychloride. The dissipation pattern of residues followed a linear first-order kinetics model for both the test fungicides. The half-life values for iprovalicarb were 9.5-13.5 days, and for copper oxychloride was 24.5 days. Based on the study, a pre-harvest interval (PHI) of 17 days is proposed for the formulation. In decontamination studies, combination treatment of 0.1% sodium bicarbonate + ultrasonication and 2% lemon water + ultrasonication has shown the highest reduction of iprovalicarb (90.02% reduction) and copper oxychloride (80.14% reduction) residues, respectively. The safety evaluation data suggest that the daily exposure at all the sampling points was less than the maximum permissible intake (MPI) calculated indicating, safety to consumers. This study will be useful for promoting effective residue management and the safe use of these chemicals for controlling fungal diseases in grapes.

Persistence evaluation of fluopyram + tebuconazole residues on mango and pomegranate and their risk assessment

The persistence of combination formulation of fluopyram 200 + tebuconazole 200-400 SC was evaluated across different agro-climates in India for the management of fungal diseases in two commercially important fruit crops, mango and pomegranate. The residues were extracted using quick easy cheap effective rugged and safe (QuEChERS) method and quantification was done on liquid chromatography-tandem mass spectrometry (LC-MS/MS). The fungicide degradation followed 1st-order kinetics and the half-lives were 2.9-6.4 days for mango, and 3.5-7.4 days for pomegranate for both the fungicides. On the basis of Organisation for Economic Co-operation and Development (OECD) maximum residue limit (MRL) calculation, 1.0 mg kg^-1 MRL was obtained for fluopyram while for tebuconazole, it was 0.5 mg kg^-1 on mango, at the pre-harvest interval (PHI) of 5 days. For pomegranate, the respective MRLs were 1.0 mg kg^-1 and 0.7 mg kg^-1 at PHI of 7 days. The dietary risk assessment study indicated that % acceptable daily intake (% ADI) and % acute reference dose (% ARfD) were much lower than 100; thus, the application of fluopyram and tebuconazole on mango and pomegranate is unlikely to present public health concern.

Determination of propineb in vegetable samples after a coprecipitation strategy for its separation-preconcentration prior to its indirect determination by FAAS

In the presented work, a coprecipitation method was developed for separation-preconcentration, and determination of trace quantities of propineb in vegetable samples. Propineb was coprecipitated by using Al(OH)₃. The zinc contents in complex structure of propineb was determined by flame atomic absorption spectrometry (AAS). The propineb concentration was calculated by using stoichiometric relationship between the zinc and propineb. Several parameters including the amount of aluminum(III) as carrier element and hydroxide concentration and sample volume were examined. The effects of matrix ions were also investigated. The preconcentration factor was calculated as 15. The limit of detection (LOD) value for propineb was calculated as 15.2 μg L^-1. The presented coprecipitation procedure was successfully applied to determination of propineb in vegetable samples.

Candida auris on Apples: Diversity and Clinical Significance

Candida auris is a multidrug-resistant nosocomial fungal pathogen. While the marine environment was recently identified as a natural niche for C. auris, the environment(s) that might have contributed to the development and spread of antifungal resistance in C. auris remains a mystery. Because stored fruits are often treated with fungicides to prevent postharvest spoilage, we hypothesized that stored fruits could serve as a possible selective force for and a transmission reservoir of antifungal-resistant isolates of pathogenic yeasts, including C. auris. To test this hypothesis, we screened fruits to study the diversity of pathogenic yeasts and their antifungal susceptibility profiles. Among the 62 screened apples, the surfaces of 8 were positive for C. auris, and all were stored apples. Whole-genome sequencing (WGS) showed that C. auris strains from apples were genetically diverse and exhibited broad phylogenetic distribution among the subclades within clade I. Interestingly, strains from apples had closely related strains from other sources in India, including from patients, hospitals, and marine environments, and from clinical strains from other parts of the world. A broad range of fungicides, including dimethyl inhibitors (DMIs), were detected in stored apples, and all C. auris isolates exhibited reduced sensitivity to DMIs. Interestingly, C. auris was not isolated from freshly picked apples. Together, the results suggest a potentially complex ecology for C. auris with agriculture fungicide application on stored fruits as a significant selective force for drug resistance in clinics.

Long-term monitoring of 155 multi-class pesticide residues in Indian vegetables and their risk assessment for consumer safety

A systematic long-term study was conducted to monitor the pesticide residues in commercially important vegetables that are produced, consumed, and exported from India. Residues of 155 commonly used pesticides were determined in 966 samples of cabbage, green chilli, and okra grown in North and North-Western part of India. The residues were extracted using modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method and quantified by gas chromatography-mass spectrometry and liquid chromatography tandem-mass spectrometry. Acetamiprid, cypermethrin, imidacloprid, metalaxyl, and profenofos were the most frequently detected pesticides. No pesticide was detected in 94.4% cabbage, 34.5% green chilli, and 61% okra samples. The chronic risk assessment due to the dietary exposure of the pesticides was evaluated for Indian adult and child. The results suggested that the detected residue levels in vegetables were within safe limits and their consumption will not pose any dietary risk to the consumers.