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 coefficient Crop coefficient Crop coefficients are properties of plants used in predicting evapotranspiration (ET). The most basic crop coefficient, "K", is simply the ratio of ET observed for the crop studied over that observed for the well calibrated reference crop under the same conditions. formula_1 Potential evapotranspiration (PET), is the evaporation and transpiration that potentially could occur if a field of the crop had an ideal unlimited water supply. RET is the reference ET often denoted as ET. Even in agricultural crops, where ideal conditions are approximated as much as is practical, plants are not always growing (and therefore transpiring) at