Pesticide Usage and Comparative Analysis of Pesticide Residues in Conventionally Grown and Organic-Certified Vegetables in North Central Province, Sri Lanka

Purpose: The main objectives of this study were to identify the types of pesticides used by the vegetable farmers in North Central Province (NCP) of Sri Lanka and analyze the residue levels of five pesticides; Thiamethoxam, Tebuconozole, Profenofos, Chlorpyrifos, and Chlorentroniliprole on conventionally grown bitter guard, brinjal, and angled luffa (n =40×3) in NCP and in different organic certified vegetables (n=42).
Research method: A standardized questionnaire was used to collect demographic information and details of pesticides used by vegetable farmers in the NCP. Pesticide residues in both conventionally grown and organic vegetables were analyzed using modified QuECHERS extraction method and GC-MS analysis.
Findings and Values: Among the many pesticides used by the vegetable farmers in NCP, three most commonly used insecticides were Tebufenozide (14.3%), Carbosulfan (13.7%) and Abamectin (12.4%). The GC-MS analysis data revealed that 22.5% of brinjal, 15% of angled luffa and 5% of bitter gourd samples were positive for Thiamethoxam (0.105 ±0.023 - 1.020 ±0.021 ppm) or Tebuconazole (0.090 ±0.007 - 0.180 ±0.041 ppm). Notably, 15% of brinjal samples exceeded the maximum residue limit (MRL) for Thiamethoxam (0.3 ppm) as stated by the Codex Alimentarius Commission. None of the organic certified vegetable samples had detectable levels of pesticide residue. Overall, this study suggests that vegetables produced in the NCP can contain harmful levels of pesticide residues. Therefore, providing proper training on safe pesticide handling practices to farmers and establishing a methodical screening procedure for pesticide residue in vegetables are important to ensure the safety of the vegetables produced in the NCP.