Dissipation and evaluation of hexaflumuron residues in chinese cabbage grown in open fields.

The dissipation and residue behavior of hexaflumuron in Chinese cabbage ( Brassica pekinensis ) under different treatments were investigated at two main cabbage-growing areas in China. The dissipation rates of hexaflumuron in cabbages and soils fit a first-order decay process very well. The dissipation times for 50% of the hexaflumuron in cabbage and soil were 3.37 and 3.01 days from Hunan province and 5.58 and 3.68 days in Tianjin, respectively, when Chinese cabbage was treated with 180 g of active ingredient (ai)/ha. Hexaflumuron residual times in cabbage and soil were influenced strongly by the application rate and frequency. The application regimen of hexaflumuron in the cabbage field, a rate of 120 g of ai/ha with two applications at a 7 day interval and a 21 day preharvest interval, was recommended from the point of view of ensuring food safety. The residual levels of hexaflumuron in cabbages were lower than the standards of the "Positive List System for Agricultural Chemical Residues in Foods" based on the recommended application regimen.