Behavior of beta cyfluthrin and imidacloprid in/on mango (Mangifera indica L.)

Dissipation behavior and dietary exposure risk of pesticides in Brussels sprout evaluated using LC-MS/MS

In this study, the dissipation behavior and dietary exposure risk of eight pesticides in Brussels sprout were evaluated under greenhouse conditions. Brussels sprout samples were collected 0, 7, 14, and 21 days after the last pesticide treatment. Ultra-high performance liquid chromatography with tandem mass spectrometry was used for sample analysis. Recovery rates at different concentrations of pesticides (0.01 and 0.1 mg/kg) were in the range of 70.2–104.5%, and the relative standard deviations were ≤ 10.6%. The pesticide residues in Brussels sprouts were determined for each treatment. For acephate, etofenprox, imidacloprid, indoxacarb, alpha-cypermethrin, zeta-cypermethrin, fludioxonil, and oxytetracycline, the half-lives were, respectively, 11.3, 9.8, 11.3, 15.8, 10.6, 13, 9.1, and 8.2 d and the dietary intake rates were, respectively, 2.90%, 0.81%, 0.7%, 1.19%, 0.06%, 0.24%, 0.05%, and 0.36% of the acceptable daily intake. The findings of this study provide important insights into the establishment of maximum residue limits in the Republic of Korea and pesticide control measures for Brussels sprout.

Co-encapsulation of imidacloprid and lambda-cyhalothrin using biocompatible nanocarriers: Characterization and application

A well-known strategy for managing pest resistance is application of mixture of pesticides. Conventionally formulated pesticides have several environmental incompatibilities. The use of biocompatible and biodegradable nanocarriers in formulating pesticides could improve environmental protection. In this study, a mixture of imidacloprid and lambda-cyhalothrin was co-encapsulated for the first time using liposomes as nanocarrier to simultaneously deliver these insecticides. Ethanol injection was used to produce self-assembled liposomes. The formed nanoliposomes were coated with different concentrations of chitosan. Nanoparticles were characterized by dynamic light scattering (DLS), scanning electron microscope (SEM) and FT-IR spectroscopy. The encapsulation efficiencies of lambda-cyhalothrin and imidacloprid were about 93% and 51%, respectively. The insecticide carrying liposomes had a size and surface charge of 57 nm and +0.6 mV, respectively. The size and surface charge of the particles produced were increased to 69 nm and +31 mV after being coated with chitosan (0.1%, W/V). In this study, residual activity of technical grade imidacloprid, lambda-cyhalothrin and their mixture and the effect of adjuvants used in commercial and nano formulations of these insecticides on Myzus persicae Sulzer was investigated. The insecticidal effects and duration of residual activity of nano-formulations was correlated with concentration of chitosan in final formulation. In accordance with the life cycle of M. persicae, using the mixture of imidacloprid and lambda-cyhalothrin improves the residual effect over their use alone. The use of lipid nanocarriers makes the improvement even further and can be a better alternative to conventional combination of these insecticides due to their more environmental friendliness.

Dissipation of neonicotinoid insecticides imidacloprid, indoxacarb and thiamethoxam on pomegranate (Punica granatum L.)

Neonicotinoid insecticides such as imidacloprid, indoxacarb and thiamethoxam are widely used for control of a large number of insect pests of pomegranate crop. Their residue levels were evaluated on pomegranate fruits over 2 years during the same cropping season. The QuEChERS analytical method in conjunction with LC-MS/MS was validated to analyse the insecticides on pomegranate fruits with peel (whole fruit), without peel (aril) and in the field soil. The method performance was satisfactory with the limit of quantification (LOQ) of 0.005 mg/kg which was below the maximum residue limits (MRLs) in pomegranate for the 3 compounds. A first order reaction kinetics was observed for the three insecticides with the half -life of degradation of 8-11.1 days for imidacloprid; 7.4-8.4 days for indoxacarb and 9.8-14.2 days for thiamethoxam. Though the insecticides are systemic in nature, the residues in the edible pomegranate aril were always < LOQ. The maximum residue levels of imidacloprid on pomegranate was less than its MRL of 1 mg/kg, so the pre-harvest interval (PHI) required was 1 day only. For indoxacarb, 31-42 days PHI was needed for the residues to reduce to its MRL of 0.02 mg/kg. The PHI of thiamethoxam was 46-77 days, the time required for its residues to reduce to its MRL of 0.01 mg/kg. Higher rainfall possibly facilitated faster dissipation of imidacloprid residues from pomegranate whereas indoxacarb and thiamethoxam remained unaffected. The results of the study can be utilized to incorporate these three chemicals in the plant protection program of pomegranate and fixation of MRL in India.

Dissipation kinetics of beta-cyfluthrin and imidacloprid in tea and their transfer from processed tea to infusion

Dissipation kinetics of mixed formulation consisting beta-cyfluthrin and imidacloprid in tea crop under an open field ecosystem was investigated. The mixed formulation was applied on tea plant at recommended (27 + 63) and double the recommended (54 + 126g a.i./ha) dose and residues were determined using gas chromatography-electron capture detector and high performance liquid chromatography-photodiode array detector for beta-cyfluthrin and imidacloprid, respectively. The limit of quantification of analytical method was 0.05µg/g and the average recoveries were ranged from 88.36% to 103.49% with relative standard deviations of less than 6% at three spiked levels. The experimental results showed that in the green tea leaves imidacloprid dissipated faster than beta-cyfluthrin with the half-life ranging between 1.20-1.39 and 2.89-3.15days, respectively. The beta-cyfluthrin residues present in the processed tea not transferred into the tea infusion during the infusion process and imidacloprid transferred in the range 43.12-49.7%. On the basis of the transfer of residues from processed tea to infusion, a waiting period of 17 days for tea plucking after pesticide application at recommended dose may be suggested.

Residue dynamics of spirotetramat and imidacloprid in/on mango and soil

Spirotetramat is a unique insecticide having both phloem and xylem mobility and imidacloprid, a neonicotinoid insecticide, is one of the most widely used in the world. The combination formulation is very effective against sucking pests of mango. Residue dynamics of spirotetramat and imidacloprid in/on mango and soil was studied following application of the combination formulation, spirotetramat 12% + imidacloprid 12% (240 SC) at 90 and 180 g a.i. ha(-1). Spirotetramat residues in/on mango fruits were 0.327 and 0.483 mg kg(-1) after giving 3 applications at 90 and 180 g a.i. ha(-1), respectively. The residues remained on mango fruits for 7 days and dissipated with the half-life of 3.3 and 5.2 days, respectively. Residues of spirotetramat-enol, the major metabolite of spirotetramat in plant, were not detected in mango fruits. Initial residues of imidacloprid on mango fruits from the two treatments were 0.329 and 0.536 mg kg(-1), respectively. Imidacloprid residues remained on mango fruits beyond 15 days and dissipated with the half-life of 5.2 and 8.2 days. The residues of spirotetramat, spirotetramat-enol and imidacloprid were found below quantifiable limit of 0.05 mg kg(-1) in mature mango fruits and field soil at harvest.

A comparative study on the persistence of imidacloprid and beta-cyfluthrin in vegetables

In an effort to compare the persistence of imidacloprid and beta-cyfluthrin, when applied through a ready mix formulation, Solomon 300 OD @ 200 and 400 mL ha(-1) in the fruits of brinjal, tomato and okra, the present study has been made. The study indicated that the dissipation of these insecticides irrespective of fruits followed concentration dependent first order kinetics. The degradation constant and half live value of beta-cyfluthrin varies between -0.287 and -0.642 day(-1) and 1.07 and 2.41 days while that of imidacloprid between -0.21 and -0.34 day(-1) and 1.98 and 3.30 days respectively suggesting that the persistence of beta-cyfluthrin is lower than that of imidacloprid in fruits of these vegetables. Moreover, the persistence of these insecticides when compared between different fruits, it is highest in brinjal followed by tomato and least in okra, a probable clue of which has been proposed based on the non-enzymatic antioxidant content of the fruits.

Extraction, cleanup, and chromatographic determination of imidacloprid residues in wheat

This study presents an improved method for quantitative analysis of imidacloprid residues in wheat grain using high performance liquid chromatography. The study used chromatographic response (in terms of peak height) as a quantitative tool for determination instead of peak area. The peak height of imidacloprid showed a very good linear correlation (R(2) = 0.999) when compared with absolute values at six different concentrations. The limit of detection was found to be 0.01 μg/mL. The recovery of imidacloprid residues in spiked wheat grain at three levels (0.03, 0.05, and 0.1 μg/g) was in the range of 79%-88% with %RSD 5.72 at 0.05 μg/g (w/w) and between 87% and 93% with %RSD 3.55 at 0.1 μg/g (w/w). At 0.03 μg/g (w/w) level, recovery was not within the recommended range of 70%-110%. Therefore, the lowest limit of quantification for this method was found to be 0.05 μg/g.