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,
Panama Canal Railway the Caribbean islands, and also included some African slaves. Many of these workers had come to Panama to seek their fortune and had arrived with little or no identification. Many died with no known next of kin, nor permanent address, nor even a known surname. Disease and exhaustion took a heavy toll on workers. The medical community did not learn about the connection between mosquitoes and malaria for another 40 years, and had no effective ways to prevent transmission of the disease. The Panama Canal Railroad Company sold the corpses of workers to medical schools abroad, using the income to