Uredo rangelii (myrtle rust) can be regarded as a member of the Puccinea psidii sensu lato (s.l., in the broad sense) complex. U. rangelii was only recently separated from P. psidii s.l. in a study of P. psidii collections (Simpson et al., 2006). Two collections on Myrtus communis from Argentina and Syzgium jambos from Jamaica had morphologically distinct urediniospores, which were newly described as U. rangelii. The urediniospores of P. psidii are completely echinulate and ellipsoidal to obovoid, compared to those of U. rangelii which are obovoid to pyriform with a smooth patch (tonsure) free of echinulations; an important taxonomic feature warranting the designation of a new species. Additionally the wall of the spore is slightly thicker and the size slightly larger in U. rangelii (Simpson et al., 2006). The teliospores are indistinguishable from P. psidii (Carnegie pers. comm., in New South Wales, Environment, Climate Change and Water, 2011). No telemorph stage is known for U. rangelii.\r\n

The DNA sequence of the rDNA ITS, tef-1a and ß-tubulin regions of U. rangelii are indistinguishable from those of P. psidii, and this species gives a positive result in the nested PCR developed to detect P. psidii (Langrell et al., 2008 in Carnegie et al., 2010; New South Wales, Environment, Climate Change and Water, 2011).

As U. rangelii was only recently separated from P. psidii s.l. (Simpson et al., 2006), it is likely that literature pertaining to guava rust, including host range and impact, includes reference to disease caused by U. rangelii (Carnegie et al., 2010).

The known hosts of Uredo rangelii are in the tribes Myrteae and Syzgieae (Simpson). Known susceptible taxa include Myrtus communis, Syzgium jambos, Agonis, Callistemon and Syncarpia. Given the wide phylogenetic separation of these taxa, other new host records can be expected (Simpson et al., 2006; Carnegie et al., 2010).

Uredo rangelii is pathogenic to plants belonging to the Myrtaceae family; a family to which many Australian native species like the Callistemons and Eucalyptus belong, the range of plants infected include Agonis flexuosa (willow myrtle), Callistemon viminalis (bottlebrush) and Syncarpia glomulifera (turpentine). Initial symptoms of U. rangelii may appear as small (1-5mm) purple flecks on young leaves, often with a faint chlorotic halo. These later develop into masses of characteristic bright yellow to orange powdery spores which may occur on both leaf surfaces. In severe infection these pustules may enlarge and coalesce. Pustules may turn grey with age (Carnegie et al., 2010). The rust affects young shoots and the growing tip of plants. The leaves become curled and distorted and new growth is killed.

Based on the current distribution and spread of the disease, the Myrtle Rust National Management Group (NMG) in December 2010 concluded that it was not technically feasible to eradicate the rust in Australia. A series of response plans which focus on community education and reducing the impact of myrtle rust on the natural environment and commercial plantations has been developed. Quarantine restrictions have been put in place to prevent the sale of plants that have been infected with myrtle rust and the movement of infected plants interstate.

Containment operations were carried out at the initial infection site and the three other infected sites. Measures included weekly fungicide applications and diseased material was removed and destroyed (Carnegie et al., 2010).