what is dutch elm disease and how does it spread
Dutch elm disease Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Although believed to be originally native to Asia, the disease was accidentally introduced into America and Europe, where it has devastated native populations of elms that did not have resistance to the disease. It has also reached New Zealand. The name "Dutch elm disease" refers to its identification in 1921 and later in the Netherlands by Dutch phytopathologists Bea Schwarz and Christine Buisman who both worked with Professor Johanna Westerdijk.[1][2] The disease affects species in the genera Ulmus and Zelkova, therefore it is not specific to the Dutch elm hybrid.[3][4][5]
Columbian exchange The history of syphilis has been well-studied, but the exact origin of the disease is unknown and remains a subject of debate.[25] There are two primary hypotheses: one proposes that syphilis was carried to Europe from the Americas by the crew of Christopher Columbus in the early 1490s, while the other proposes that syphilis previously existed in Europe but went unrecognized.[26] These are referred to as the "Columbian" and "pre-Columbian" hypotheses.[26] The first written descriptions of the disease in the Old World came in 1493.[27] The first large outbreak of syphilis in Europe occurred in 1494/1495 in Naples, Italy, among the army of Charles VIII, during their invasion of Naples.[26][28][29][30]