A US attempt to control musk thistle using a specific weevil between 1969 and 1972 had unintended consequences. The weevil, intended to target only the invasive plant, began attacking native thistle species. This resulted in negative impacts on local thistle populations, including a reduction in seed production for an endangered variety. The incident highlights the risks associated with biological control methods and the need for thorough pre-release assessments. Experts emphasize that carefully evaluating potential non-target effects is crucial when implementing invasive species management programs. The case serves as a cautionary tale about disrupting ecological balance. The unforeseen consequences demonstrate the complexities of ecological intervention.