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,
Scald (barley disease) of the disease involves the use of clean and/or treated seeds, resistant cultivars, crop rotation, residue management, and foliar fungicides. Cultivars with scald resistance are available in all major barley growing areas. The level of resistance occurs along a spectrum and the degree of resistance that is required to effectively control the disease will depend on the region where it is grown, cropping practices that reduce initial disease inoculum, wetter conditions and fungal pathotypes. Foliar fungicides can be used to effectively control disease development. Product selection, application rates and timing, depend upon numerous factors. The availability of fungicides as a