Application of indoxacarb for managing shoot and fruit borer of eggplant (Solanum melongena L.) and its decontamination

Abstract

Indoxacarb was applied at 75 and 150 g a.i. ha− 1 for two years to an eggplant (Solanum melongena L.) crop grown in the field plots in order to evaluate its efficacy for management of the lepidopteron pest, shoot and fruit borer. The residues of the insecticide were quantified by high-pressure liquid chromatography (HPLC). The mean initial deposits of indoxacarb on eggplant fruits were found to be 2.60–2.634 mg kg− 1 and 3.64–3.68 mg kg− 1 from the two rates of applications, respectively. They declined with time and reached to non-detectable (< 0.02 mg kg− 1) after 15–20 d. Residues dissipated with a half-life of 3.0–3.8 d from both first and second-year application. A 3 d waiting period for harvest of fruits after insecticide application and processing resulted in the residue levels that were below the Codex maximum residue limit (MRL) of 0.5 mg kg− 1 thereby achieving a maximum safety and minimum risk to consumers. The best combination of chemicals for decontamination of indoxacarb was found to be by washing with a mixture of alkali and potassium permanganate (KMnO4) thereby resulting in the removal of 67.5% and 59.2 % residues for 5 and 10 μ g g− 1 spiking doses, respectively. Major products formed on reaction of indoxacarb with alkali were identified by electron spray ionization chromatography/mass spectrometry (ESI/MS). The per cent reduction on the weight and number basis of treated eggplant plots were compared to those observed in control plots to demonstrate the effectiveness of indoxacarb treatment on shoot and fruit borer population.