Persistence and dissipation of ready pre-mix formulation (novaluron + indoxacarb) in/on tomato (Lycopersicon esculentum Mill.) and its leaching in soil

Abstract

A field experiment was conducted to study the persistence behaviour in tomato fruits and soil underneath and effect of processing on the reduction of residues of ready pre-mix formulation (Novaluron 5.25% + Indoxacarb 4.5% SC). Samples of tomato fruits and soil were collected periodically on 0 (1h), 1, 3, 5, 7, 10 and 15 days after applications. Residues were estimated by gas chromatography (GC) equipped with capillary column and electron capture detector (ECD). Per cent recoveries at the fortification levels of 0.01, 0.10 and 0.25 mg kg−1 in tomato fruits and at 0.01 and 0.05 mg kg−1 in soil were in the range of 82-94 per cent depicting validity of methods used for present studies. Limit of detection was 0.005 mg kg−1. Dissipation in tomato fruits followed first order kinetics with half life period from 1.40 - 2.48 days at both the doses of novaluron as well as indoxacarb. Residues decreased substantially during household processing among which peeling was found most effective which resulted 80-89 % reduction. For sandy loam soil under tomato crop, half-life period was found to be in the range of 0.63 to 2.17 days at single and double doses, respectively, for both novaluron as well as indoxacarb following first order kinetics. In leaching experiment carried out under laboratory conditions, 55 - 60% retention of novaluron and 70 - 75% retention of indoxacarb were observed up to 10 cm soil in both the doses, showing their very less mobility in soil. Residues were not detected after 40 cm depth of soil in both the doses. Since, residues of novaluron and indoxacarb were not detected in any of the leachate fractions of soil, hence, these may be safe for soil and ground water contamination.