Costa_2026_Pest.Manag.Sci__

BACKGROUND: Leucoptera coffeella is a key pest of coffee crops in Brazil, causing significant damage by mining coffee leaves. Reports of reduced effectiveness of chemical control measures highlight the need to investigate potential resistance mechanisms. This study aimed to evaluate the risk of control failure, resistance levels and enzymatic activity in Brazilian field populations of L. coffeella exposed to neurotoxic insecticides. RESULTS: A total of 35 field populations of L. coffeella were collected and tested in the laboratory using filter paper discs treated with insecticide solutions. After 48 h of exposure, mortality rates, median and 95% lethal concentrations (LC(50) and LC(95)), and median resistance ratios (RR(50)) were determined. Control failure risk was identified in 34.3% and 62.9% of populations for abamectin, chlorpyrifos, deltamethrin and profenophos. Five populations exhibited low to very high resistance to abamectin (RR(50) = 5.5-794), and two populations showed very high resistance to chlorpyrifos (RR(50) = 142 and 727) and deltamethrin (RR(50) = 1281 and 1656). Enzymatic assays revealed lower acetylcholinesterase activity in Rio Paranaba II and higher glutathione S-transferase activity in Rio Paranaba I, followed by Carmo do Paranaba populations. CONCLUSION: Our findings demonstrate widespread resistance and altered enzymatic activity in L. coffeella populations across Brazilian coffee-growing regions. These results highlight the urgent need to incorporate resistance monitoring and alternative control strategies into integrated pest management programs to ensure sustainable coffee production. 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.