ABSTRACT
Site or habitat selection is of considerable significance in the management of plant diseases. Because of their different climatic conditions, diseases may be avoided or reduced by choosing to plant in different sites, regions, or altitudes. One of the most important factors in mountain agriculture is altitude, which has profound effects on the climate. Traditional farmers often know intimately the qualities of the many potato cultivars they grow, and therefore grow cultivars at different altitudes according to their zone of adaptation. Asexually propagated crops such as cassava, potatoes, yams, sugar cane, and sweet potatoes in the lower elevations of the tropics frequently become heavily infected with pathogens, especially virus diseases. In some traditional societies, priests and other leaders had a major responsibility to mandate or advise on planting sites, especially when land was shared by the larger community.
