Degradation dynamics of a new neonicotinoid insecticide, imidaclothiz, in tea-field ecosystems in China

As a new neonicotinoid insecticide, imidaclothiz has been recently used in tea-fields in China. In this paper, the degradation dynamics of imidaclothiz in fresh tea, dried tea and soil were studied. Imidaclothiz residue was extracted, with acetonitrile and cleaned up by a modified ENVI (TM)-Carb method. HPLC with UV detection was employed to determine concentrations of imidaclothiz residues. The accuracy and precision of this method were validated. Two kinds of dosages of wettable powder concentrate with 10% imidaclothiz were applied in field, the recommended dose (450 g hm(-2)) and the double of the recommended dose (900 g hm(-2)). In the recommended dose group, the degradation dynamics coincided with the following equations: Ct = 2.721e(-0.224t), = 0.5 16e(-0.138t), and Ct = 0.714e(.0.096t) for fresh tea, dried tea and soil, respectively. In the double dose group, the dynamics equations were Ct = 5.225e(-0.159t), Ct = 0.918e(-0.145t), and Ct = 2.662e(-0.038t), respectively. The final residue level was lower than the tentative maximum residue limit (MRL) of imidaclothiz on fresh tea, with a harvest interval of 45 days.