Insecticide residue analysis on vegetable crops through Rapid Bioassay of Pesticide Residue (RBPR) technique in Nepal

Abstract

Insecticides applied on food crops and vegetables reduce the pest population and leave chemical residues that may result in serious health consequences. In Nepalese context, farmers use pesticides repeatedly to get rid of pests and also don’t consider the waiting period. The study was conducted to evaluate the amount of pesticide residue after application of different organophosphate and carbamate insecticides in vegetable crops. Five insecticides were used in seven different combinations (Dimethoate, Malathion, dichlorvos, Chlorpyriphos, Dimethoate + dichlorvos, Malathion + Chlorpyriphos and Carbofuran) and applied in mustard leaves and broccoli. The residues were assessed using the “Rapid Bioassay of Pesticide Residue technique”. Results exhibited that Chlorpyriphos treated mustard leaves were edible in 3 DAA (Days after application) and in 6 DAA when sticker was applied with treatment. With or without sticker Dimethoate followed by Malathion applied mustard leaves were edible in 6 DAA. With or without sticker Dichlorvos took longest (12 DAA) to reach the safe limits for mustard leaves. In contrary the Dichlorvos treated broccoli was edible in 3 DAA but took 6 DAA when sticker was applied. Malathion treated broccoli, with and without sticker, was edible in 6 DAA. For both crops Carbofuran exhibited anomalous nature showing lower residue level in the beginning and higher later. When both vegetables were applied treatments with stickers, they showed significantly higher residue and took longer time to reach edible limit. The applied insecticides took relatively longer to reach safe level in mustard leaf as compared to broccoli. The study suggests use of Chlorpyriphos for mustard leaves and Malathion for broccoli with at least 6 days of waiting period, with or without use of sticker.