Residual dynamics and safely applying technology of pyridaben in vegetable-soybean

In order to monitor pyridaben residue in vegetable-soybean and apply pyridaben scientifically and safely in pest control, the residual content and degradation dynamics of pyridaben in vegetable-soybean were studied by GC-ECD method and field experiment. Meanwhile the safe usage technology demonstration experiments were set up. The established quantitative determination method is simple, accurate and available with 88.8% ~ 94.0% average recoveries of pyridaben residue in vegetable-soybean, 2.2% ~ 4.7% RSD, 0.01 ng LOD and 0.005 mg·kg^-1 LOQ. The original sediment of pyridaben is different for different treatments and the residue degradation dynamics follows the exponential regression equation: ,C=A·e^kt with a correlation coefficient (|r|) range of 0.964 8 ~ 0.995 3 (P < 0.01). The degradation rate of pyridaben in vegetable-soybean is basically consistent in the late seasons of 2004 and 2005 for the different treatments. Pyridaben degradation coefficient (|k|) is 0.181 0 ~ 0.203 9. T_1/2 and T_0.99 of pyridaben are 3.4 ~ 3.8 d and 22.6 ~ 25.4 d respectively. Based on conventional application method, vegetable-soybean is sprayed once or twice (at 7 d intervals) in the demonstration fields with 84.38 g·hm^-2 effective composition of pyridaben. The final residue in vegetable-soybean products is less than 0.1 mg·kg^-1, with average residual contents of 0.054 mg·kg^-1, 0.059 mg·kg^-1 at 18 d after application. The quality of the products meets the minimum requirement level (MRL) of Japan.