Persistence and Dissipation of Combination–Mix (Spirotetramat+Imidacloprid) on Chilli (Capsicum annum L.)

A supervised field trial was conducted on chilli with combination mix (spirotetramat 120+imidacloprid 120) – 240 w/v SC at two doses of 120+120 and 240+240 g.ai. ha⁻¹, applied thrice at 10 d interval starting from fruit setting stage. Residues of spirotetramat, spirotetramat enol and imidacloprid were estimated using High Performance Liquid Chromatography. The limit of quantification of the above chemicals was found to be 0.05 mg kg⁻¹ for chilli. The mean initial deposit of spirotetramat in green chilli was 1.2 and 1.752 mg kg⁻¹ for lower and higher dose respectively, dissipated and reached below quantification limit within 15 and 20 d. The half life values were 2.01 and 3.09 d for both the treatments. The mean initial deposit of imidacloprid in green chilli was 2.53 and 3.15 mg kg⁻¹ for lower and higher dose respectively, dissipated and reached below quantification limit within 30 and 35 d. The half life values were 5.82 and 5.77 d for both the treatments. No residues above limit of quantification could be detected in red chilli at harvest. Spirotetramat enol metabolite was not detected in green and red chilli at any stage during the study period.