Dissipation kinetics of trifloxystrobin and tebuconazole on apple (Malus domestica) and soil--a multi location study from north western Himalayan region

Combined toxicity of trifloxystrobin and fluopyram to zebrafish embryos and the effect on bone development

Trifloxystrobin (TRI) is a methacrylate fungicide, and fluopyram (FLU) is a new pyridylethylbenzamide fungicide and nematicide. Both are often detected in water bodies and may be highly toxic to many aquatic organisms. Unfortunately, the aquatic biological risks of single FLU or a mixture of trifloxystrobin and fluopyram have not been reported. In this study, zebrafish was selected as the test organism to investigate the combined toxicity of trifloxystrobin and fluopyram to zebrafish. After zebrafish embryos exposed to three pesticide solutions, Alcian-blue staining, Alizarin-red staining and quantitative PCR (qPCR) were performed. The results indicated that 96h-LC50 of TRI was 0.159 mg·L-1 to zebrafish embryo, which was highly toxic. The 96h-LC50 of FLU to zebrafish embryos was 4.375 mg·L-1, being moderately toxic. The joint toxicity to zebrafish embryos(FLU at 96h-LC50 and TRI at 96h-LC50 in a 1:1 weight ratio to form a series of concentration treatment groups) was antagonistic. Both trifloxystrobin and fluopyram also inhibited the skeletal development of zebrafish and showed to be antagonistic. The results of qPCR indicated upregulations of different genes upon three different treatments. TRI mainly induced Smads up-expression, which may affect the BMP-smads pathway. FLU mainly induced an up-expression of extracellular BMP ligands and type I receptor (Bmpr-1a), which may affect the BMP ligand receptor pathway. The 1:1 mixture (weight ratio) of trifloxystrobin and fluopyram induced a reduction of the genes of extracellular BMP ligand (Smads) and type I receptor (Bmpr1ba), which may down-regulate BMP signaling and thus attenuating cartilage hyperproliferation, hypertrophy and mineralization. The results warren an interest in further studying the effect of the two fungicides in a mixture on zebrafish.

Behavior of trifloxystrobin and propineb as combination product in tomato (Solanum lycopersicum) and their risk assessment for human health

Fungicides have their own unique characteristics and modes of action; a combination formulation [combination product (combi product)] of trifloxystrobin and propineb was applied to tomatoes for their dissipation kinetics and to ensure consumer safety. The combi product was applied at a 10-day interval with standard (61.25 + 1072.75 g a.i. ha-1 ) and double (122.5 + 2145.50 g a.i. ha-1 ) doses. The efficient analytical method was established using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) approach followed by LC-MS. The maximum residue levels of 0.15 and 0.35 mg kg-1 of trifloxystrobin were detected in tomato fruits immediately after application at standard and double doses, respectively. The corresponding levels of propineb as carbon disulfide were 0.47 and 0.90 mg kg-1 , respectively. Considering trifloxystrobin (0.7 mg kg-1 ) codex maximum residue limit and propineb as dithiocarbamate (3.0 mg kg-1 ) European Commission maximum residue limit in tomato, a pre-harvest interval of 1 day can be proposed. The anticipated residue contributions of both fungicides were far less than the acceptable daily intake. The targeted hazard quotient and hazard index were also less than 1 for both fungicides. Furthermore, the theoretical maximum residue contribution was less than its maximum permissible intake, which indicates that the consumption of tomatoes containing the measured value of each fungicide residue could not pose any health risks.

Effect of microorganisms on degradation of fluopyram and tebuconazole in laboratory and field studies

Nowadays, chemical pesticides are the most widespread measure used to control crop pests and diseases. However, their negative side effects prompted the researchers to search for alternative options that were safer for the environment and people. Pesticide biodegradation by microorganisms seems to be the most reasonable alternative. The aim of the laboratory studies was to assess the influence of Bacillus subtilis and Trichoderma harzianum, used separately and combined together, on fluopyram and tebuconazole degradation. In field studies, the degradation of fluopyram and tebuconazole after the application of the biological preparation in apples was investigated. The results from the laboratory studies show that the greatest decomposition of fluopyram and tebuconazole was observed in tests with T. harzianum in a range of 74.3-81.5% and 44.5-49.2%, respectively. The effectiveness of fluopyram degradation by B. subtilis was 7.5%, while tebuconazole inhibited bacterial cell growth and no degradation was observed. The mixture of microorganisms affected the degradation of fluopyram in a range of 8.3-24.1% and tebuconazole in a range of 6.1-23.3%. The results from the field studies show that degradation increased from 3.1 to 30.8% for fluopyram and from 0.4 to 14.3% for tebuconazole when compared to control samples. The first-order kinetics models were used to simulate the residue dissipation in apples. For the determination of pesticide residues, the QuEChERS method for apple sample preparation was performed, followed by GC-MS/MS technique. Immediately after the treatments, the maximum residue level (MRL) values for tebuconazole were exceeded, and it was equal to 100.7% MRL for the Red Jonaprince variety and 132.3% MRL for the Gala variety. Thus, preharvest time is recommended to obtain apples in which the concentration of pesticides is below the MRL and which can be recognized as safe for humans.

Dissipation rate and exposure risk of trifloxystrobin in dry climatic field environments

The investigation of the magnitude of residues after application of a pesticide is important to ensure consumer safety and is also a regulatory requirement to grant authorization. To address those issues, the behavior of trifloxystrobin residues was investigated in outdoor strawberry and cucumber cultivations, following the recommended and more critical agricultural practices under Egyptian dry climatic conditions. Fruits were collected at several pre-harvest intervals and analyzed with the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction protocol followed by liquid chromatography-tandem mass spectrometry. The limit of quantitation of the method was 0.001 mg kg−1. When trifloxystrobin was applied on the field, the half-lives were 2.4 days in cucumbers and 6.2 days in strawberries. Risk assessment showed that chronic and acute dietary exposure to residues following the investigated agricultural patterns are of no concern to consumers.

Triazole fungicide tebuconazole induces apoptosis through ROS-mediated endoplasmic reticulum stress pathway

Tebuconazole (TEB) is a common triazole fungicide that has been widely applied in the treatment of fungal diseases. It is reported that TEB could exert harmful effects on mammals' health. However, the molecular mechanism involved in TEB toxicity remain undefined. Our study aimed to investigate the mechanisms of TEB-induced toxicity in intestinal cells. We found that TEB stimulates apoptosis through the mitochondrial pathway. Additionally, TEB triggers endoplasmic reticulum (ER) stress as demonstrated by the activation of the three arms of unfolded protein response (UPR). The incubation with the chemical chaperone 4-phenylbutyrate (4-PBA) alleviated ER stress and reduced TEB-induced apoptosis, suggesting that ER stress plays an important role in mediating TEB-induced toxicity. Furthermore, inhibition of ROS by N-acetylcysteine (NAC) inhibited TEB-induced ER stress and apoptosis. Taken together, these findings suggest that TEB exerts its toxic effects in HCT116 cells by inducing apoptosis through ROS-mediated ER stress and mitochondrial apoptotic pathway.

Simultaneous determination, dissipation and decontamination of fungicides applied on cabbage using LC-MS/MS

A method for simultaneous determination of carbendazim and tebuconazole residues in cabbage was developed and validated in LC-MS/MS. Samples were extracted and purified following the modified QuEChERS procedure, which enabled the elution of carbendazim and tebuconazole at 0.96 and 5.31 min, respectively. LOD and LOQ were 0.0005 and 0.0015 mg kg^-1, respectively. Mean recovery was in the range of 78.94 to 104.89% for carbendazim and 76.07 to 98.62% for tebuconazole. The field samples recorded residues of 0.274 and 0.481 mg kg^-1; and 0.194 and 0.392 mg kg^-1 at single and double dose for carbendazim and tebuconazole, respectively. Half-life values were 2.17 and 2.99 for carbendazim and 2.74 and 2.81 for tebuconazole at single and double dose, respectively. Decontamination with saltwater wash followed by cooking and lemon water wash found superior in the removal of residues more than 90%.

Tebuconazole induces ROS-dependent cardiac cell toxicity by activating DNA damage and mitochondrial apoptotic pathway

Tebuconazole (TEB) is a common triazole fungicide that is widely used throughout the world in agriculture applications. We previously reported that TEB induces cardiac toxicity in rats. The aim of this study was to investigate the underlying mechanism of the toxicity induced by TEB in cardiac cells. TEB induced dose-dependent cell death in H9c2 cardiomyoblasts and in adult rat ventricular myocytes (ARVM). The comet assay and western blot analysis showed a concentration-dependent increase in DNA damage and in p53 and p21 protein levels 24 h after TEB treatment. Our findings also showed that TEB triggered the mitochondrial pathway of apoptosis as evidenced by a loss of mitochondrial transmembrane potential (ΔΨm), an increase in Bax/Bcl-2 ratio, an activation of caspase-9 and caspase-3, a cleavage of poly (ADP-ribose) polymerase (PARP) and an increase in the proportion of cells in the sub-G1 phase. In addition, TEB promoted ROS production in cardiac cells and consequently increased the amounts of MDA, the end product of lipid peroxidation. Treatment of cardiomyocytes with the ROS scavenger N-acetylcysteine reduced TEB-induced DNA damage and activation of the mitochondrial pathway of apoptosis. These results indicate that the genotoxic and cytotoxic effects of TEB are mediated through a ROS-dependent pathway in cardiac cells.

Residue analysis and kinetics modeling of thiophanate-methyl, carbendazim, tebuconazole and pyraclostrobin in apple tree bark using QuEChERS/HPLC-VWD

Winter is the key period for the control of apple diseases, and fungicides are needed to protect the trunk or main branches. Fungicide residue in apple tree bark is an important basis for the action of the pesticide, but there are no reports on analytical methods or dissipation patterns. In this work, thiophanate-methyl, carbendazim, tebuconazole and pyraclostrobin were selected as typical fungicides and a new QuEChERS-HPLC-VWD(QuEChERS extraction followed by high-performance liquid chromatography detection with a variable wavelength detector) analytical method was developed to estimate their residue kinetics in apple tree bark during the winter months. In the pretreatment step, the sorbent for the clean-up of extracts was optimized as 60 mg/ml primary secondary amine and a gradient-elution model followed by a variable wavelength detection was developed for instrumental analysis. Then this method was validated and applied to the analysis of apple tree bark samples with the linearity range of 0.010-50.00 mg/L, quantification limit range of 0.028-0.080 mg/kg and recovery range of 86.1-101.4%. The dissipation kinetics of thiophanate-methyl and pyraclostrobin could be described by the first-order and two-phase kinetics models, respectively. For carbendazim and tebuconazole, two new models were developed to describe their residue kinetics.

Persistence and dissipation kinetics of tebuconazole in apple, tomato, chilli and onion crops of Himachal Pradesh, India

Tebuconazole is a broad-spectrum fungicide extensively used worldwide for the control of many diseases such as powdery mildew and scab in apple, early blight of tomato, anthracnose of chilli, white rot and purple blotch of onion etc. Maximum residue level of this compound has not been worked out on these crops in India; the persistence and dissipation kinetics of tebuconazole on apple, tomato, chilli and onion were studied following three foliar applications of the formulation Folicur 430 SC at a standard dose (X) 322, 268.75, 215 and 215 g a.i./ha and at double dose (2X) 645, 537.5, 430 and 430 g a.i./ha, respectively, to work out the safe waiting periods and half-life period of tebuconazole. Extraction was done using QuEChERS method and cleanup by using dispersive solid-phase method. Tebuconazole residues were estimated on gas chromatograph-mass spectrometry (GC-MS). The recovery of tebuconazole in fortified matrix was above 90% with a limit of quantification (LOQ) at 0.05 mg kg^-1. The initial deposits of tebuconazole on apple at two locations under study ranged from 1.986-2.011 mg kg^-1at X dose to 3.698-3.843 mg kg^-1 at 2X dose. The initial deposits in tomato, chilli and onion were 1.129, 1.760 and 1.169 mg kg^-1 at X dose and 2.213, 2.784 and 2.340 mg kg^-1, respectively at the 2X dose. Dissipation of the fungicide followed first-order of kinetics and the half life of degradation ranged from 1.30-2.25 days at X dose to 1.40-2.62 days at 2X days on different crops under study. Residues declined below the determination limit (LOQ) of 15 and 20 days after spraying, respectively, at X and 2X dose in apple; 7 and 10 days in tomato; 10 and 15 days in chilli and onion. Waiting periods of 5, 2, 7 and 12 days, respectively, are suggested for apple, tomato, chilli and onion at 2X dose.

Persistence, dissipation, and risk assessment of a combination formulation of trifloxystrobin and tebuconazole fungicides in/on tomato

Multi-locational supervised field trials were conducted in different agro-climatic regions in India to study dissipation of trifloxystrobin and tebuconazole in tomato after spraying a combination formulation (trifloxystrobin 25% + tebuconazole 50%, 75WG) at recommended doses: (i) single (trifloxystrobin 87.5 g a.i. ha^-1 + tebuconazole 175 g a.i. ha^-1) and (ii) double (trifloxystrobin 175 g a.i. ha^-1 + tebuconazole 350 g a.i. ha^-1). Fruit samples were extracted with ethyl acetate using a modified QuEChERS method. The residues (parent fungicides + metabolite) were analyzed and confirmed by GC-ECD and GC-MS, respectively. The half-life (t_1/2) of trifloxystrobin and tebuconazole in tomato varied from 1.08 to 1.72 and 1.13 -to 1.64 days at single; and 1.27 to 2.13 and 1.24 to 1.96 days at double dose, respectively. Since maximum residue limit (MRL) at pre-harvest interval (PHI) of 5 days is impractical, as tomato is usually harvested and consumed almost everyday after the last spray, the risk assessment was performed at minimum PHI of 1 day. Accordingly, on the basis of supervised field trial data and using OECD MRL calculator, MRL of 0.5 and 1.5 mg kg^-1 at single dose were proposed for trifloxystrobin and tebuconazole in/on tomato, respectively.

Residue Distribution, Dissipation Behavior, and Removal of Four Fungicide Residues on Harvested Apple after Waxing Treatment

The residue distribution and dissipation of pyrimethanil, fludioxonil, cyprodinil, and kresoxim-methyl, which were introduced during postharvest waxing treatments of apples, were investigated. In addition, different residue removal methods were tested for the four fungicides in apples, and the removal efficiencies were compared. A multiresidue analytical method was developed based on quick, easy, cheap, effective, rugged, and safe method (QuEChERS) for the determination of the fungicide residues in apples. The dissipation study demonstrated that there was no significant change of fungicide residue magnitude during a 40-day storage process under ambient temperature. The fungicide residues in apples by wax treatment were shown to be very much stable. The results of residue distribution study demonstrated that waxing treatment may help to reduce the risk of pesticide when only the pulp was consumed. In the residue removal study, results suggested that higher temperature and the addition of acetic acid can improve the residue removal efficiency.

Tebuconazole induces triazole-resistance in Aspergillus fumigatus in liquid medium and soil

Aspergillus fumigatus is the mainly leading cause of invasive aspergillosis associated with significant morbidity and mortality in immunocompromised patients. However, triazole resistance in A. fumigatus has increased dramatically throughout the world nowadays. The emergence of triazole resistance has aroused growing concern. This research was conducted to assess if the resistance in A. fumigatus and its associated mutations in the cpy51A gene could be induced during its exposure to tebuconazole in liquid medium and in soil. The results indicated that the resistance in A. fumigatus with mutations of TR46/Y121F/T289A could be induced by tebuconazole in liquid medium. Nine resistant strains without any mutation in cyp51A were isolated in soil treated with tebuconazole at levels of 0.5-5.0 mg kg^-1 after incubation for 120 d. The two (HI-30 and HI-36) of the nine resistant isolates were caused by overexpression of AtrF, AfuMDR1, cyp51A and cyp51B and hereditary stability. This strongly implies that conventional application of tebuconazole for plant protection will cause resistance of A. fumigatus to triazole medicals in agricultural soils.

Adsorption-desorption and hysteresis phenomenon of tebuconazole in Colombian agricultural soils: Experimental assays and mathematical approaches

The adsorption-desorption, hysteresis phenomenon, and leachability of tebuconazole were studied for Inceptisol and Histosol soils at the surface (0-10 cm) and in the subsurface (40-50 cm) of an agricultural region from Colombia by the batch-equilibrium method and mathematical approaches. The experimental K_fa and K_d (L kg^-1) values (7.9-289.2) decreased with depth for the two Inceptisols and increased with depth for the Histosol due to the organic carbon content, aryl and carbonyl carbon types. Single-point and desorption isotherms depended on adsorption reversibility and suggested that tebuconazole showed hysteresis; which can be adequately evaluated with the single-point desorption isotherm and the linear model using the hysteresis index HI. The most suitable mathematical approach to estimate the adsorption isotherms of tebuconazole at the surface and in the subsurface was that considering the combination of the n-octanol-water partition coefficient, pesticide solubility, and the mass-balance concept. Tebuconazole had similar moderate mobility potential as compared with the values of other studies conducted in temperate amended and unamended soils, but the risk of the fungicide to pollute groundwater sources increased when the pesticide reached subsurface soil layers, particularly in the Inceptisols.

Residue analysis and risk assessment of tebuconazole in jujube (Ziziphus jujuba Mill)

In this study, a sensitive and reliable analytical method, based on a modified Quick, Easy, Cheap, Effective, Rugged and Safe procedure, was established for determination of tebuconazole in jujube. After extraction with acetonitrile, the samples were cleaned up by dispersive solid-phase extraction with primary secondary amine, and determined by high-performance liquid chromatography tandem mass spectrometry. At fortification levels of 0.01, 0.1 and 2.0 mg kg^-1 , the average recoveries of tebuconazole in jujube were in the range 97.6-101.9%, with relative standard deviations of 1.5-3.5%. The dissipation and residual levels of tebuconazole in jujube under field conditions were investigated. Tebuconazole dissipated relatively slowly in jujube, with a half-life of 33.0 days. The terminal residue experiments of tebuconazole in jujube were conducted in four locations in China and the risk was evaluated using risk quotients (RQ). RQ values were found to be significantly lower than RQ = 1, indicating that the risk to human health of using the recommended doses of tebuconazole in jujube was not significant. This study could provide guidance for the safe and reasonable use of tebuconazole in jujube and serve as a reference for the establishment of limit of maximum residue in China.

Comparison of the residue persistence of trifloxystrobin (25%) + tebuconazole (50%) on gherkin and soil at two locations

Residue study of trifloxystrobin and tebuconazole on gherkin was carried out at two locations (Bangalore and Gouribiddunur, India) after applications at the standard and double doses of 75 + 150 and of 150 + 300 g ha(-1) of the formulated product, trifloxystrobin (25%) + tebuconazole (50%) (Nativo 75 WG). The fungicides were determined by gas chromatography (GC) and confirmed by gas chromatography-mass spectrometry (GC-MS). Extraction and purification of the samples were carried out by Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method after validating the analytical parameters. Initial residues of trifloxystrobin on gherkin fruits were 0.335 and 0.65 mg kg(-1) at Bangalore, and 0.34 and 0.615 mg kg(-1) at Gouribiddunur. Tebuconazole residues were 0.842 and 1.682 mg kg(-1) at Bangalore, and 0.71 and 1.34 mg kg(-1) at Gouribiddunur. Residue dissipation of the fungicides followed first-order rate kinetics. Trifloxystrobin residues dissipated at the half-life of 2.9-3.7 days, and tebuconazole at 3.2 days. At the standard dose treatment, trifloxystrobin residues dissipated to below the maximum residue limit (MRL) of 0.2 mg kg(-1) (European Union) within 3 days at both the locations. Residues of the metabolite CGA 321113 was less than the limit of quantification (LOQ; 0.05 mg kg(-1)) on all sampling days. Tebuconazole residues dissipated to below its MRL (0.05 mg kg(-1)) within 14 and 11 days, at Bangalore and Gouribiddunur, respectively. From the two trials, it was concluded that the required pre-harvest interval (PHI) for the combination formulation was 14 days. Application of Nativo 75 WG should be given before flowering to allow the residues to dissipate below the MRLs at harvest.

Track of fate and primary metabolism of trifloxystrobin in rice paddy ecosystem

Trifloxystrobin, a strobilurin fungicide, has been widely applied to control fungal diseases in various crops, especially in rice cultivation. However, its residual profile in rice paddy that was highly linked to its ecological risk still remains poorly understood. To elucidate the fate and primary metabolism of trifloxystrobin in rice paddy, a simple and efficient analytical method was developed using the DisQuE extraction kit combined with GC-μECD and GC-EI-MS/MS analyses. As a result, methodological recoveries of trifloxystrobin fortified in paddy water, soil and rice straw ranging from 0.005 to 2 mg kg(-1) (mg L(-1) for water) were acquired from 87.6% to 109.1% with relative standard deviation (RSD) from 1.9% to 9.5% (n=5), and the limit of detection (LOD, signal to noise (S/N)=3) and the limit of quantification (LOQ, S/N=10) were 6.3×10(-4) mg L(-1) and 2.09×10(-3) mg L(-1), respectively, which indicates the favorable accuracy, precision and sensitivity of the method for effective monitoring of the trace amounts of residual trifloxystrobin in the rice paddy. Furthermore, dissipation of residual trifloxystrobin was in accordance with the first-order rate equation, showing the half-lives from 0.7 to 7.5 days, illustrating that trifloxystrobin generally degraded in a rapid rate in the rice paddy. Additionally, trifloxystrobin acid identified as the primary metabolite of trifloxystrobin in the rice paddy via GC-EI-MS/MS analysis was found to be dominantly accumulated in the paddy water and maintained up to 2.41 mg L(-1) within 14 days, suggesting that long-term and frequent application of this fungicide may pose a high risk towards aquatic organisms in surrounding aqueous ecosystems through paddy drainage. Taken together, our data serve as a useful tool for monitoring residual trifloxystrobin in rice paddy ecosystem and also provide a basis for in-depth understanding of environmental behavior and ecological risk posed by this fungicide.

Dissipation, residues, and safety evaluation of trifloxystrobin and tebuconazole on ginseng and soil

Supervised field trials at two locations in 2012 and 2013 were conducted to evaluate the dissipation, terminal residues, and safety evaluation of Nativo 75 water dispersible granule (WG) (25 % trifloxystrobin + 50 % tebuconazole) on ginseng and soil following foliar application at a recommended dose 150 (50 + 100) and 1.5 times of the recommended dosage 225 (75 + 150) g a.i. ha(-1). The average recoveries of trifloxystrobin and tebuconazole at three spiking levels in ginseng root, stem, and leaf and in soil were in the ranges of 81.0-96.8 % and 80.2-97.5 % with relative standard deviations (RSDs) of 4.92-13.13 % and 4.67-8.35 %, respectively. The half-lives of trifloxystrobin and tebuconazole were 5.92-9.76 days and 4.59-7.53 days, respectively. The terminal residues were all below the maximum residue limits (MRLs) of EU, USA, Canada, Japan, and South Korea. The food safety was evaluated by comparing the estimated daily intake (IEDI) with its acceptable daily intake (ADI). IEDI values calculated from residue data were found to be far less than the ADI on ginseng. Therefore, it would be unlikely to cause health problems induced by Nativo 75 WG use on ginseng at a dosage of 150-225 g a.i. ha(-1).

Residue levels and dissipation behaviors for trifloxystrobin and tebuconazole in mango fruit and soil

An evaluation of residue levels of trifloxystrobin and tebuconazole was carried out on mango fruits after treatments with the combined formulation, trifloxystrobin (25 % w/w) and tebuconazole (50 % w/w), at standard and double doses of 250 + 500 and 500 + 1000 g a.i. ha(-1), respectively. Extraction and purification of the mango fruit samples were carried out by the QuEChERS method after validating the analytical parameters. Determination of the fungicides was carried out by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The limits of detection (LOD) and limits of quantification (LOQ) for both fungicides were 0.015 μg mL(-1) and 0.05 mg kg(-1), respectively. The residue levels of trifloxystrobin for standard and double-dose treatments were 0.492 and 0.901 mg kg(-1) and for tebuconazole were 0.535 and 1.124 mg kg(-1), respectively. A faster dissipation of tebuconazole in mango fruit was observed compared with that for tebuconazole. Dissipation of trifloxystrobin and tebuconazole in mango followed first-order kinetics, and the half-lives were 9 and 6 days, respectively. The preharvest intervals (PHI), the time taken for the combined residues of trifloxystrobin and tebuconazole to dissipate to their permissible levels (maximum residue limits), were 14 and 20 days for standard and double doses, respectively. At harvest, mature mango fruit and soil were free from fungicide residues.

Field dissipation of trifloxystrobin and its metabolite trifloxystrobin acid in soil and apples

The dissipation of trifloxystrobin and its metabolite trifloxystrobin acid in apples and soil was studied, and the half-life (DT₅₀) was estimated in a field study carried out at three different locations for apples and four different locations for soil. Trifloxystrobin was sprayed on apples at 127 g a.i./ha for the dissipation study. Samples of apple and soil for the dissipation experiment were collected at time intervals of 0, 1, 3, 7, 14, 21, 30, and 45 days after treatment. The quantification of residues was done by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The DT₅₀ of trifloxystrobin ranged from 0.54 to 8.8 and 4.8 to 9.5 days in soil and apples at different latitude sites. Photolysis may be the main dissipation pathway for trifloxystrobin, and the number of sunshine hours may be the main factor affecting the trifloxystrobin dissipation rate in the field. For trifloxystrobin acid residues in soil and apples, it first increased and then began decreasing. It was indicated that the risk of trifloxystrobin application in shorter sunshine hour area should be considered.

Dissipation and residues of trifloxystrobin and its metabolite in rice under field conditions

Residue analysis of trifloxystrobin and its metabolite (CGA 321113) in rice matrices, paddy water, and soil was developed using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and high-performance liquid chromatography-tandem mass spectrometry. The method was used to evaluate the dissipation rate of trifloxystrobin and CGA 321113 in rice seedling, soil, and paddy water as well as the residual level in harvest rice (grain, hull, straw) and soil. The results demonstrated that the dissipation half-lives of trifloxystrobin in rice seedling, soil, and water were 1.9 d to 4.7 d, 0.35 d to 0.54 d, and 0.28 d to 0.51 d, respectively. The final total residue of trifloxystrobin and CGA 321113 was highest in rice hull and lowest in paddy soil. The highest total residues in husked rice, rice hull, straw, and paddy soil at 28 d after spraying were 0.39 mg kg(-1), 3.82 mg kg(-1), 0.29 mg kg(-1), and 0.15 mg kg(-1), respectively. According to the final residue data and the maximum residue limits of trifloxystrobin in rice grain and straw (Codex Alimentarius) and in rice hull (US Environmental Protection Agency), 28 d could be recommended as the preharvest interval for trifloxystrobin application in the rice field. The data show that CGA 321113 constitutes a small amount of the final total residues in rice matrices, whereas it is much higher than its parent compound in soil samples.