Blights are spread through the earth and air, destroying crops on a vast scale. If a community’s livelihood relies on the production of one type of crop or that crop is the main source of food, blights can by devastating. Potato blight rots the crop making it inedible.

During the Irish potato famine of 1845-47 1m people died of starvation and about the same amount emigrated. In the 1860s another form of blight destroyed 2m hectares of grape vines in Europe, almost wiping out the wine industry.

Blight on the rye harvest in Salem, USA, in the 17th century didn’t wipe out the crop. Instead it infected it with a poisonous fungus that could survive the heat of the baking process. When the bread was eaten it caused what is called ergot poisoning, which has hallucinogenic effects. It is believed that many of the 'witches' of the Salem witch trials were actually driven mad because of the infected rye in their bread.