Thiacloprid residues and its safety evaluation in Darjeeling tea.

In order to examine the persistence behavior, safety evaluation and utilization of residue data for fixation of thiacloprid MRL, a supervised field trial in tea was conducted at Darjeeling. The HPLC analysis of thiacloprid in green tea leaves indicates that the initial deposits of 2.14 and 3.95 mg kg(-1), which declined gradually and persisted until day 14 to the tune of 0.23 and 0.45 mg kg(-1) respectively. The residues in processed tea samples prepared from green tea leaves of 7 and 14th day were 3.0-3.8 times less. Thiacloprid did not infuse to tea liquor from processed tea. The half-life value in green tea leaves ranged from 4.29 to 4.31 days. Considering the EU MRL value of 10 mg kg(-1) and risk assessment calculation, thiacloprid at 30 g a.i. ha(-1) appears to be safe in plant protection schedules and first round of plucking of green tea leaves on day 7 is recommended.

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.

Persistence and dissipation kinetics of deltamethrin on chili in different agro-climatic zones of India.

Multi-location supervised field trials were conducted at four different agro climatic locations in India to evaluate the dissipation pattern of deltamethrin on chili. Deltamethrin 10 EC was applied on chili @17.5 and 35 g a.i. ha(-1), samples of green chili were drawn at different time intervals and that of red chili and soil at harvest time and quantified by gas liquid chromatography equipped with electron capture detector. The identity of residues were confirmed by Gas Chromatograph-Mass Spectrophotometer in selective ion monitoring mode in mass range 181, 253 m/z. Limit of quantification of the method was found to be 0.01 mg kg(-1). Half-life of deltamethrin at application rate of 17.5 g a.i. ha(-1) varied from 0.36 to 1.99 days and at double the application rate was found to range from 0.38 to 2.06 days. Residues of deltamethrin were found below its determination limit of 0.01 mg kg(-1) in red chili and soil. On the basis of the data generated, Deltamethrin 10 EC has been registered for use on chili in India and its Maximum Residue Limit has been fixed as 0.05 µg/g.

Persistence and safety risk assessment of propineb in Indian tea.

A supervised field trial was conducted on tea with propineb at 1,750 and 3,500 g a.i./ha at two locations (Assam and Darjeeling), applied thrice at an interval of 10 days during the year 2006-2007. Propineb residue was measured spectrophotometrically at 435 nm in terms of CS2. The initial deposit of propineb in green tea leaves were found to be in the range of 16.26-35.96 mg/kg and the residue persisted up to 10 days irrespective of doses and locations with half-life value ranging from 2.24 to 2.43 days and preharvest interval of 17.17-21.37 days. Made tea residues ranged from 9.27 to 20.86 mg kg(-1) on 7 days and no residues could be detected on 14 days. Infusion study indicated that propineb did not infuse into tea liquor from made tea. The limit of determination was found to be 0.1 mg kg(-1) in terms of propineb for green tea leaves, made tea, and tea liquor. The tea applied with the recommended dose of propineb is safe for consumption as liquor.