Stephen Goldson is a grassland entomologist who works to find ways to suppress exotic pest species running riot in Aotearoa's pastures. In 1991, after a painstaking search and much research, Goldson and his group introduced a tiny parasitoid wasp, about the size of a very small ant, from South America to kill the Argentine stem weevil that can devastate our pastures. The plan worked very well for around 20 years - then the weevil found a way to fight back and scientists think it has achieved this through rapid evolution. Goldson joins Kim to discuss the battle against the weevil and what's next for biocontrol, the country's unique pasture ecology, and the collision of our bush and pasture ecosystems. Goldson is Deputy Director at Lincoln University's Bio-protection Research Centre that is focused plant pest management, a Principal Scientist in the Crown Research Institute AgResearch, and strategy advisor to the Prime Minister's chief science advisor Professor Sir Peter Gluckman.