During the early 1900s, prickly pear, advancing more than a thousand hectares a day, blanketed more than 20 million hectares of Queensland and northern New South Wales in a horror of spines. This case study explains how a devastating and seemingly intractable weed was tamed with the aid of a tiny moth from South America. This success was due to federal leadership, intergovernmental collaboration and a persistent, well-funded scientific endeavour.