The residue and degradation of bifenthrin in cotton and soil

To evaluate the safety in repeated annual field applications of the insecticide bifenthrin to cotton plants,the final residue and degradation dynamics of bifenthrin were studied in cotton leaves,seeds and corresponding soil,respectively,by collecting the samples from the trials both in Jinan and Hangzhou areas in 2010 and 2011.The chemical was analyzed by gas chromatography(GC).The degradation behavior of bifenthrin can be described by first-degree dynamic pattern in the cotton leaves and the soil.The half-lives of bifenthrin were 4.2~6.7 and 10.6~16.0 d,respectively.The residues in the cotton seeds and the soil were as low as below limit of detection(LOD) of 0.01 mg.kg-1,which were lower than the maximum residue limit(MRL) of 0.5 mg.kg-1.We suggest that 10% bifenthrin soluble concentrate liquid(SL) be used in cotton against Aphid with dosage 9~18 aig.hm-2,and sprayed 1~2 times per season.The pre-harvest interval(PHI) is defined to be 14 days.