Chestnut blight is a serious disease of chestnut trees caused by the fungus Cryphonectria parasitica. The fungus does little damage to host trees in its native range in Asia, but has devastated American chestnut when it was accidentally introduced to the USA more than 100 years ago via infected planting stock. The disease was introduced into Europe in the 1930s where it affects species such as the European or ‘sweet’ chestnut. It has since spread to most parts of the continent, causing serious damage in orchards and forests. Chestnut blight was detected for the first time in Britain in 2011 on planted imported trees, but is now considered eradicated. However, annual surveys and vigilence are needed to ensure that the UK remains free of the disease.