Residue dynamics of common insecticides in tomato fruits under Nigerian field conditions

Tomato ( Solanum lycopersicum L.) is a vital vegetable crop in Nigeria, however its production often necessitates intensive insecticide use, raising concerns about residue contamination in harvested fruits. This study investigated the persistence and safety of residues from eight commonly applied insecticides in tomato fruits under field conditions in Nigeria. The insecticides evaluated were cypermethrin, lambda-cyhalothrin, deltamethrin, endosulfan, dimethoate, dichlorvos, diazinon and carbaryl. Field applications were conducted at recommended label rates, and tomato fruit samples were collected at 1, 2, 4, and 5 days post-treatment. Insecticide residue levels were quantified using gas chromatography, and their dissipation patterns over time were analyzed. The results revealed that cypermethrin, lambda-cyhalothrin, deltamethrin, endosulfan, dimethoate, dichlorvos, diazinon and carbaryl had residues falling below established Maximum Residue Limits (MRLs) within 1 day to 7 days after application. However, lambda-cyhalothrin, diazinon and cypermethrin exhibited rapid degradation compared to deltamethrin, endosulfan, dimethoate, dichlorvos, and carbaryl from 1 to 5 days after application. Conversely, deltamethrin, cypermethrin, dimethoate, and carbaryl persisted on the fruits and degraded slowly for extended periods. Cypermethrin, deltamethrin and lambda-cyhalothrin exhibited residues below the Acceptable Daily Intake (ADI) at 5 days post-treatment These findings underscore the critical need for adherence to pre-harvest intervals and the selection of insecticides with shorter residual activity to mitigate potential consumer health risks. This research provides practical insights for implementing safer pest management practices and effective residue management in Nigerian tomato production systems.