BACKGROUND Bordeaux mixture is a copper‐based fungicide commonly used in vineyards to prevent fungal and bacterial infections in grapevines. However, this fungicide may adversely affect the entomological component, including insect pests. Understanding the impacts of Bordeaux mixture on the vineyard pest Lobesia botrana is an increasing concern in the viticultural production. RESULTS Bordeaux mixture had detrimental effects on the development and reproductive performance of L. botrana . Several physiological traits were adversely affected by copper‐based fungicide exposure, including a decrease in larval survival and a delayed larval development to moth emergence, as well as a reduced reproductive performance through a decrease in female fecundity and fertility and male sperm quality. However, we did not detect any effect of Bordeaux mixture on the measured reproductive behaviors (mating success, pre‐mating latency and mating duration). CONCLUSION Ingestion by larvae of food contaminated with Bordeaux mixture had a negative effect on the reproductive performance of the pest L. botrana , which could affect its population dynamics in vineyards. Although this study highlighted collateral damage of Bordeaux mixture on L. botrana , the potential impact of copper‐based fungicides on vineyard diversity, including natural predators is discussed and needs to be taken in consideration in integrated pest management. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.