Persistence behaviour and safety risk evaluation of pyridalyl in tomato and cabbage.

A field experiment was set up to evaluate persistence behaviour of pyridalyl in tomato, cabbage and cultivated field soil over two consecutive seasons. An analytical method was developed to analyze pyridalyl residues in different matrices and duly validated, based on single laboratory method validation criteria. Pyridalyl residues were detected and quantified using a gas chromatograph equipped with an electron capture detector. The compound exhibited low persistence in tomato, cabbage and soil. A safe waiting period of 17-18 d after final insecticide application needs to be maintained before harvesting the crop. Both dietary and soil ecological risk were assessed and it was found that the harvested vegetables were toxicologically safe for consumption. However, there was concern about insecticidal toxicity against the algal population of soil which needs to be reconfirmed by further studies.

Persistence behavior of metamifop and its metabolite in rice ecosystem.

A field experiment was conducted to determine the persistence of metamifop in transplanted rice crop for two seasons. Metamifop 10% EC was applied at two doses: 100 g a.i. ha-1 and 200 g a.i. ha-1 at 2-3 leaf stage of Echinochloa crusgalli. The residues of metamifop along with its major metabolite, N-(2-fluorophenyl)-2-hydroxy-N-methylpropionamide (HFMPA), were estimated in rice plant, field water and soil using Liquid Chromatography Mass Spectrometry. Limit of detection and limit of quantification of the method for both the compounds were set at 0.003 µg g-1 and 0.010 µg g-1 respectively. Metamifop showed less persistence in field water and rice plant as compared to soil samples. Presence of HFMPA was recorded in rice plant and soil. Both the compounds were found below level of quantification in harvest samples of straw, grains, husk and soil. A safe waiting period of 52 d was suggested for harvesting of rice when metamifop was applied at 100 g a.i. ha-1 (recommended dose).

Dissipation kinetics and risk assessment of chlorfenapyr on tomato and cabbage.

A field experiment was conducted over two seasons to evaluate the dissipation kinetics and assess the risks of chlorfenapyr in tomato and cabbage following foliar application of chlorfenapyr 10% SC at 100 and 200 g a.i. ha-1. Samples of tomato, cabbage, and soil were analyzed and quantified by gas chromatography-electron capture detector (GC-ECD). The limit of detection (LOD) and limit of quantification (LOQ) of chlorfenapyr were found to be 0.01 and 0.03 mg kg-1, respectively, in tomato, cabbage, and soil. The dissipation of chlorfenapyr followed first-order kinetics. The compound showed less persistence in both the vegetables and soil as the calculated half-life values of chlorfenapyr ranged between 4.54 and 7.74 days considering two different doses and seasons. The residue was below detection limit in all the untreated plant and soil samples. The pre-harvest interval (PHI) of chlorfenapyr in both the vegetables was determined to be 9-14 days regardless of dose or season. The theoretical maximum residue contribution (TMRC) of chlorfenapyr was calculated for tomato and cabbage and was found to be lower than the maximum permissible intake (MPI) of the compound. Therefore, the application of chlorfenapyr at the recommended dose in tomato and cabbage for crop protection seems to be safe from both environmental contamination and consumer safety standpoints.

Persistence of chlorfluazuron in cabbage under different agro-climatic conditions of India and its risk assessment.

A multilocational field trial was conducted at 4 locations in India-Rajasthan, Gujarat, Madhya Pradesh, and West Bengal-to determine the persistence in cabbage of chlorfluazuron applied twice at 75 and 150 g active ingredient ha-1 . Cabbage head samples were collected from each replicated plot on 0 (2 h after spraying), 1, 3, 5, 7, 10, and 15 d after final insecticide application, including an untreated control. Chlorfluazuron residue in cabbage and field soil was estimated by high-performance liquid chromatography using a photo diode array detector. The limit of determination and limit of quantification of the method were recorded as 0.05 and 0.10 µg g-1 , respectively. Results revealed that chlorfluazuron dissipated linearly with progress of time, following first-order kinetics. The mean (± standard deviation) half-life value of chlorfluazuron in cabbage was found to be 7.18 ± 0.71 d, considering different locations and treatments. The residue was below the level of quantification in the harvested cabbage and soil samples. Harvesting cabbage in the experimental location, at least on day 7, after 2 applications of chlorfluazuron at the recommended dose, may not pose any ill effect for Indian adults. Environ Toxicol Chem 2017;36:3028-3033. © 2017 SETAC.

Persistence behaviour of thiamethoxam and lambda cyhalothrin in transplanted paddy.

A field study was conducted in Pre-Kharif season 2007 on paddy to determine the persistence of thiamethoxam (12.6%) and lambda cyhalothrin (9.4%) [in a 'Readymix' formulation Alika 247 ZC], following the application of 33 g. a.i. ha⁻¹ (T1) and 66 g. a.i. ha⁻¹ (T2). Spraying of insecticide was done during milking stage of the crop (63 days after transplantation). Thiamethoxam and lambda cyhalothrin residues were estimated by HPLC and GLC respectively. The half-life values were 5.2-5.8 and 4.8 days for thiamethoxam and lambda cyhalothrin respectively. No residue was detected in the harvested paddy, straw, grain, and soil samples.