Abstract: In order to explore the effects of 28-high brassinolide on the degradation of deltamethrin in leeks（Allium tuberosum）, with leeks as the test material, 0.01% high-brassinolide solvable agent was used as the test agent, 0.04% 24-epbrassinolide solvable agent was used as the control agent, and water was taken as the control to spray on the leeks 1 day before deltamethrin root irrigation. The leek samples were taken at 0, 1, 2, 3, 5, 8, 12, 16 d after root irrigation of 20 mg/L deltamethrin, respectively. The modified QuEChERS method was used to pretreat the leek samples, and gas chromatography-mass spectrometry was used to detect deltamethrin residue in leek samples. The results showed that one day after deltamethrin root irrigation, the residue of deltamethrin in leeks treated with 0.01% 28-high brassinolide diluted 1 000 times was the lowest, which was 19.73% lower than that in water control. The residues of deltamethrin in leeks treated with once dilution of 0.01% 28-high brassinolide （1 000 times）, twice dilution of 0.01% 28-high brassinolide （1 000 times） and water control all reached the maximum on one day after root irrigation, which were 0.046 0, 0.058 3, 0.057 3 mg/kg, respectively. Treated with 500 times, 1 000 times and 2 000 times dilution of 0.01% 28-high brassinolactone, respectively, one day after deltamethrin root irrigation, the leeks treated with 0.01% 28-high brassinolactone dilution of 1 000 times had the lowest deltamethrin residue, which was significantly lower than water control and 0.01% 28-high brassinolactone treatment at 2 000 times dilution, but no significant difference was found between the treatment and 0.01% 28-high brassinolactone treatment at 500 times dilution.

Key words: Leek（Allium tuberosum）, 28-high brassinolide, deltamethrin, residue of pesticide, degradation