Analysis of Pesticide Residues in Rice Grains and Investigation of Farmers' Usage in Suphan Buri and Kanchanaburi Provinces

Abstract

Recently, an increase of pesticide use can cause pesticide residue above standard limit which could affect on agricultural product export. This research aimed to analyze and monitor pesticide residues in rice production in Suphan Buri and Kanchanaburi Provinces. The experiment was conducted at Thailand Rice Science Institute, Suphan Buri province during 2020-2021 by collecting different rice varieties from 40 farmer's fields per province. These rice samples were extracted followed by AOAC method and analyzed pesticide residues by using validated methods of LC-MS/MS and GC-MS/MS. The limit of detection (LOD) and limit of quantification (LOQ) values of this validated methods were 0.005 and 0.01 mg/kg (ppm), respectively. The pesticide residues were detected in 18 rice samples (22.5%) from Suphan Buri province which were insecticide from organophosphate group (omethoate 2 samples) and carbamate group (carbofuran 1 sample) and fungicide which were cyproconazole (1 sample), propiconazole (7 samples), and tebuconazole (13 samples). No pesticide residue was detected in rice samples from Kanchanaburi province. In addition, the monitoring of pesticide residues in rice production in Suphan Buri and Kanchanaburi provinces was also surveyed. The results showed an invasion of thrips and brown planthopper in both provinces; however, most farmers decided to apply pesticides to control these problems especially at Suphan Buri province where farmers applied pesticide at all stages of rice development. The thiamethoxam and thiacloprid were mostly applied at seedling stage while abamectin was used at tillering and booting stages which accounted for over 70% of pesticide application at all three stages. A dirty panicle disease was a major disease found in Suphan Buri province while blast and brown spot were found in Kanchanaburi province. In this case, the difenoconazole+propiconazole were mostly applied especially at booting and heading stages at Suphan Buri province. In summary, the pesticide residues found in rice samples did not exceed the maximum residue limit of Thai regulation and Codex's MRLs. However, these pesticide residues exceeded the European Commission maximum residue levels (EU MRLs). The reduction and appropriate pesticide application should be promoted to decrease residue levels in rice products that could impact on rice export.