Growth dilution and its effect on pesticide dynamics in Okra

Abstract

Dissipation studies at single and double doses of chlorantraniliprole, thiamethoxam (25 and

50 g ai ha-1), and imidacloprid (20 and 40 g ai ha-1) were conducted on okra fruits following field application, and the residues were estimated using LC-MS/MS. The initial deposit of 0.42 and 0.80 mg kg-1 of chlorantraniliprole dissipated below quantitation level on the tenth day at single and double dosages. For thiamethoxam, the initial deposits of 0.42 and 0.71 mg kg-1 reached below quantitation level on tenth day at single dosage and on fifteenth day at double dosage; and for imidacloprid, the initial deposits are 0.10 and 0.16 mg kg-1 which dissipated below quantification level on fifth day. Growth dilution plays a significant role in the rate of dissipation of thiamethoxam when compared with imidacloprid and chlorantraniliprole when simulated dissipation rate due to growth dilution was calculated. The half-life of chlorantraniliprole, thiamethoxam and imidacloprid were 1.94 and 1.72 days, 1.88 and 1.99 days, 1.13 and 1.05 days, respectively for single and double dosages. Chlorantraniliprole, thiamethoxam and imidacloprid were found to be the safer insecticides with calculated waiting period of less than one day for single dosage.