Studies on dissipation pattern of tolfenpyrad in cabbage (Brassica oleracea var. capitata) under polyhouse conditions

Abstract

A field experiment was conducted during rabi, 2022-23 at Horticultural Polyhouse, College of Agriculture, Rajendranagar, Professor Jayashankar Telangana State Agricultural University (PJTSAU) to study the dissipation pattern of tolfenpyrad in cabbage. Tolfenpyrad15 EC @ 150 g a.i. ha-1 was sprayed at 10 days interval during the head initiation stage. The heads were collected at 0 (2 h after spray), 1, 3, 5, 7, 10, 15
and 20 days after final spray and were analyzed for residues using the validated QuEChERS method on LCMS/ MS. The limit of quantification (LOQ) of this method was 0.01 mg kg-1. The analytical method adopted for analysis on LC-MS/MS was evaluated through linearity, Limit of detection (LOD), LOQ, fortification and recovery studies. Linearity studies gave satisfactory R2 value of 0.993, while the fortification studies
at LOQ, 10 times LOQ recorded recovery in the acceptable range of 87.98-96.15 per cent. The mean initial deposit of 0.519 mg kg-1 recorded at 0 days (2 h) after final spray dissipated to 0.359, 0.329, 0.222, 0.108, 0.040 and 0.017 mg kg-1 at 1, 3, 5, 7,10 and 15 days with dissipation of 30.82, 36.60, 57.22, 79.19, 92.29, 96.72 per cent respectively, after final spray. At 20 days after second spray, it was below LOQ. The
calculated half-life and safe waiting periods under polyhouse conditions for tolfenpyrad were 2.93 and 17 days, respectively.