Plane wilt, also known as canker stain disease, is a serious disorder of plane trees, which are important amenity trees in the parks and avenues of many European cities. The disease is caused by the fungus Ceratocystis platani, which is present in the USA and Europe, but considered to be indigenous only to North America. It is thought to have been introduced into Europe in the Naples area of southern Italy during World War II, possibly arriving in infected wood from the USA used to package military supplies. Since then plane wilt has gradually spread to other European countries. In 2014 the UK became a Protected Zone to provide extra safeguards against accidental introduction of this disease on imported trees or the wood of plane.