RESUMO
Pigeonpea (Cajanus cajan L.) is an annually cultivated food and forage crop, attacked by a large number of pests mainly pod borer (Helicoverpa armigera). For the control of this insect pest, a combination of broad-spectrum insecticides viz., chlorantraniliprole and λ-cyhalothrin have been in use to reduce the pod damage and increase crop production worldwide. Therefore, a field trial was conducted to study dissipation and persistence behavior of insecticides combination (Chlorantraniliprole 9.26 % + λ-cyhalothrin 4.63 % ZC) in/on pigeonpea at the recommended dose (RD) 30 g a.i./ha and double recommended dose 60 g a.i./ha (2RD). The quantitative analysis was performed using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for chlorantraniliprole and Gas chromatography with electron captured detector (GC-ECD) for λ-cyhalothrin. The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method was validated for its accuracy, precision and sensitivity. The chlorantraniliprole persisted upto 30 days and λ-cyhalothrin persisted upto 10 days at RD and 20 days at 2RD. The half-lives (DT50) of chlorantraniliprole and λ-cyhalothrin were from 4.95 to 5.78 days and 2.48-4.33 days at recommended and double recommended dose in pigeonpea, respectively. However, residues of both insecticides measured from soil at 30th day and harvest time were below the limit of quantification (LOQ). The waiting period deciphered for chlorantraniliprole and λ-cyhalothrin applied as combi-product was 9 days at recommended dose. Dietary risk assessment (Risk quotient<1) was performed on the basis of field trial suggested the application of chlorantraniliprole and λ-cyhalothrin as combi-product at recommended dose is safe for the consumers.
