ABSTRACT
A pest species is any species which are considered undesirable. The use of the term pest is therefore subjective. A more complete definition of pest is that pests compete with humans for food or shelter, transmit pathogens, feed on humans or otherwise threaten human health, comfort or welfare. Pest control in various forms has been used extensively since the development of agriculture some 10 000 years ago. Mixing crop species in a field, optimizing planting or harvesting times and avoiding repeated planting of the same crop at the same site are long-established cultural strategies for limiting pest damage. The use of inorganic compounds in pest control was common in the nineteenth and early twentieth Centuries. Inorganic compounds were the traditional agents of herbicides, but due to problems with persistence and nonspecificity, compounds such as borates, arsenicals, ammonium sulfamate and sodium chlorate are rarely used unless semi-permanent sterility is required.
