Bayer code is a system of identifying crop plants and their pests (including weeds and diseases) by a unique code. They are a core component of a database of names, both scientific and vernacular. Plants are identified by a five letter code, other organisms by a six letter one. In many cases the codes are mnemonic abbreviations of the scientific name of the organism derived from the first three or four letters of the genus and the first two letters of the species. For example, corn (Zea mays) would be ZEAMA and potato late blight (Phytophthora infestans) PHYTIN. By providing a unique and constant code for each organism the system provides a shorthand method of recording species and avoids many of the problems caused by revisions to scientific names and taxonomy which often result in different synonyms being in use for the same species.
Although originally started by the Bayer Corporation, the official list of codes is now maintained by the European and Mediterranean Plant Protection Organization (EPPO). They are now therefore more correctly known as EPPO codes.