Persistence and Dissipation Pattern of Dimethoate 30 EC in / on Foxtail Amaranthus and Spinach

摘要

A survey was conducted to know the insecticide usage pattern in leafy vegetables and found that dimethoate was the most frequently used insecticide. A field trail was conducted to know the dissipation pattern of dimethoate in foxtail amaranthus and spinach during October - November, 2017. Dimethoate 30 EC was sprayed twice as foliar treatment at 10 days interval @ 200 and 400 g a.i ha~(-1). The samples were collected from 0,1, 3, 5, 7,10,15 and 20 days after treatment (DAT), extracted by modified QuEChERS method and analyzed by LCMS. The mean initial deposit (1 h after spraying) of dimethoate at 200 and 400 g a.i ha~(-1) were 7.25 ug g~(-1) and 19.51 ug g~(-1) for foxtail amaranthus and 18.37 ug g~(-1) and 29.46 ug g~(-1) for spinach, respectively.The residues reached below detectable level of < 0.05 ug g~(-1) at 10 days after treatment in foxtail amaranthus and 15 and 20 DAT in spinach for both doses. Half-life of dimethoate residues were 0.85 and 0.86 days in foxtail amaranthus; 2.22 and 1.12 days in spinach at 200 and 400 g a.i ha~(-1), respectively.