The North American pine wood nematode (PWN), Bursaphelenchus xylophilus, is a pest worm species that causes a disease known as pine wilt. It was discovered for the first time in the EU in Portuguese forests in 1999. Today, the entire territory of Portugal is demarcated for the presence of PWN, with a 20 km buffer zone, free from the pest, established along the Spanish border with the aim of preventing its further spread. The spread and establishment of PWN in the rest of EU territory is very likely if no strict measures are taken, as required by Decision 2012/535/EU of the European Commission, with serious economic and environmental consequences. To date, Spain has experienced five outbreaks of PWN, three of which have been successfully eradicated thanks to the EU measures and the effective work of the Spanish forest administration; and two outbreaks are currently being eradicated.