Persistence of bifenthrin in tea and its transfer from black tea to tea brew

Field experiments were conducted at two places in Tamil Nadu (India) to determine the residues of bifenthrin in black tea. Residues were quantified at different harvest intervals of ‘0’ (3 hr), 1 st , 3 rd , 5 th , 7 th , 10 th and 14 th day after acaricide application. Persistence, dissipation pattern, half-life value and safe harvest interval of the acaricide in tea were calculated. Residues of bifenthrin dissipated exponentially after application at both the locations and reached below the European Union maximum residue limit (MRL) of 5 mg kg-1 on the 10th day. Bifenthrin showed that like other acaricides it followed the first order dissipation kinetics. Half-life values varied from 2.4 to 3.2 days for bifenthrin and a safe harvest interval of 10 days is suggested for tea at the recommended dosage.