<Tr> <Th> EPPO Code </Th> <Td> CERAUL </Td> </Tr> <Tr> <Th> Distribution </Th> <Td> Europe, North America and New Zealand </Td> </Tr> <P> 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 . The disease affects species in the genera Ulmus and Zelkova, therefore it is not specific to the Dutch elm hybrid . </P> <P> The causative agents of DED are ascomycete microfungi . Three species are now recognized: </P>

What is dutch elm disease and how does it spread
find me the text answering this question