Dissipation Kinetics of Deltamethrin 10 EC in Capsicum (Capsicum Annum var. Frutescens) and Cropped Soil Under Field and Polyhouse Conditions

Abstract

The dissipation behavior of deltamethrin 10 EC (Decis®) in capsicum (Capsicum annuum var. frutescens) grown in polyhouse and open field was investigated. Two sprays of deltamethrin 10 EC @ 15 and 30g a.i./ha (150 ml/ha -recommended and 300 ml/ha- double the recommended dose), respectively were applied at 10 days intervals, initiating at button sized fruit stage. Fruit samples were collected at 0, 1, 3, 5, 7, 10, 15, 20, 25 days after second spray and the soil samples were collected at final harvest for residue analyses. Modified QuEChERS multi-residue analysis showed initial residues of 0.976 and 1.161 mg/kg recorded at 15 and 30 g a.i./ha doses, respectively in polyhouse. The residues persisted upto 7th and 10th day, reaching below quantification limit (BQL) by 10th and 15th day, respectively at both the doses. In open field, the initial deposits recorded were 0.607 and 1.924 mg/kg reaching BQL on 5th and 7th day, respectively @ 15 and 30 g.a.i./ha. The comparative results showed that half life (syn. Dissipation time 50- DT50) for deltamethrin in capsicum fruits varied from 2.05–2.45 days in polyhouse. The corresponding values in open field were 1.51–1.86 days suggesting that dissipation of deltamethrin residues took longer time in controlled conditions than open field. The soil samples analysed at harvest contained no residues. The insecticide degradation followed the first order kinetics. Since, the insecticide is not recommended under capsicum in India; the data may help to fix maximum residue limit (MRL) and pre harvest interval (PHI).