New Zealand Myrtaceae are susceptible to a strain from the Eucalyptus biotype of Austropuccinia psidii present in South America.
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ABSTRACT.- The international spread of the myrtle rust pathogen, Austropuccinia psidii, can be largely attributed to the "pandemic" biotype that has more than 450 host species. However, within South America, the putative native range of A. psidii, multiple biotypes have been characterised, each with a restricted known number of hosts. These biotypes may pose a significant biosecurity threat to countries already affected by the pandemic biotype.