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,
Sugarcane grassy shoot disease Sugarcane grassy shoot disease Sugarcane grassy shoot disease (SCGS), caused by small, parasitic bacteria, contributes to losses of 5% to 20% in the main crop of sugarcane, and these losses are higher in the ratoon crop. A higher incidence of SCGS has been recorded in some parts of Southeast Asia and India, resulting in 100% loss in cane yield and sugar production. Sugarcane is a vegetatively propagated crop, so the pathogen is transmitted via seed material and by phloem-feeding leafhopper vectors. "Saccharosydne saccharivora", "Matsumuratettix hiroglyphicus", "Deltocephalus vulgaris" and "Yamatotettix flavovittatus" have been confirmed as vectors for phytoplasma transmission in sugarcane.