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 scouting planting date, planting rate (spacing), row width, tillage operations, crop yields, pesticide names, rates, application dates and who applied them, fertilizer and lime applications and rates, weather patterns, soil type, soil test records (N, P, K, percent organic matter, and pH), irrigation availability, major pest problems, and anything else that could make scouting more effective. This history is very important when assessing signs of crop injuries, because they are generally ambiguous since similar abnormalities can have unrelated causes. It is best to always be prepared when entering the field, as one never know what kind of issues one will find.