Crop diversity fruit trees and banana plants) are cloned. A single pest or disease could threaten a whole crop due to this uniformity ("genetic erosion"). A well-known historic case was the Irish Potato Famine of 1845-1847, where a vital crop with low diversity was destroyed by a single fungus. Another example is when a disease caused by a fungus affected the monocultured 1970 US corn crop, causing a loss of over one billion dollars in production. A danger to agriculture is wheat rust, a pathogenic fungus causing reddish patches, coloured by its spores. A virulent form of the wheat disease, stem rust,
Crop art figures are found all over the world; though many do not attribute their manifestation to visitations by alien beings. Crop Circles are sometimes called crop formations, agroglyphs, or pictograms. Some are also created by recognized "landscape artists" for commercial purposes. Crop art Crop art is an environmental art practice using plants and seeds in the landscape to create statements, marks and/or images. Agnes Denes, Matthew Moore (artist), Dennis Oppenheim and Stan Herd are practitioners of Crop art. Some works of Land art, and Earth art are similar in scale, and can be seen only from aerial viewpoints. One folk art