Persistence of chlorpyriphos in okra (Abelmoschus Esculentus) fruits and soil

Abstract

Persistence of cypermethrin and chlorpyriphos in okra and soil were studied following the application of pre-mix formulation of insecticides Action 505EC (chlorpyriphos 50% + cypermethrin 5%) at single (275 g a.i. ha⁻¹) and double dose (550 g a.i. ha⁻¹). The average initial deposits of chlorpyriphos in okra were observed to be 0.07 and 0.15 mg kg⁻¹ in single and double dose, respectively, which dissipated to 92% after 10 days for both the dosages. Residues of soil under okra crop were found to be 0.15 mg kg⁻¹ at the single and 0.36 mg kg⁻¹ at the double doses. These residues persisted up to 3 days at single and 5 days at double dose. The half-life (t _1/2) periods of chlorpyriphos on okra and soil were observed to be 0.6 days and 1.9 days for single and double dose, respectively. Residues of chlorpyriphos reached below detectable level (BDL) of 0.01 mg kg⁻¹ in okra fruits after 7 days at single dose and in 15 days in double dose. In soil, residues of chlopyriphos persisted up to 5 and 7 days in single and double dose, respectively. Following foliar applications of a insecticide formulation (Action 505EC, (chlorpyriphos 50% + cypermethrin 5%) on okra at @ 275 and 550 g active ingredient (a.i.) ha⁻¹ resulting in active applications of chlorpyriphos at the rate of 250 and 500 g a.i. ha⁻¹ the average initial deposits of chlorpyriphos in okra were observed to be 0.07 and 0.15 mg kg⁻¹, respectively. These residue levels dissipated to 92% after 10 days at both the dosages. Residues of soil under the okra crop were found to be 15 mg kg⁻¹ at the single and 36 mg kg⁻¹ at the double dose. The residues persisted up to 3 days at the single and 5 days at the double dose. The half-life (t _1/2) periods of chlorpyriphos on okra were observed to be 0.6 days for application rates, and 1.9 days for soil. Okra fruits and soil samples collected on the 7th and 15th day after application did not show any chlorpyriphos residues above their determination limits of 0.01 and 0.005 mg kg⁻¹, respectively.

Keywords:

• Action-505EC
• chlorpyriphos
• residues
• okra
• soil

Acknowledgemnts

The authors wish to express their gratitude to the Head of the Department of Entomology for providing research facilities.