Austropuccinia

Austropuccinia is a monotypic genus of rust (a type of plant pathogen) native to South America with the only species Austropuccinia psidii, commonly known as myrtle rust, guava rust, or ʻōhiʻa rust. It affects plants in the family Myrtaceae. It is a member of the fungal complex called the guava rust (Puccinia psidii) group. The spores have a distinctive yellow to orange colour, occasionally encircled by a purple ring. They are found on lesions on new growth including shoots, leaves, buds and fruits. Leaves become twisted and may die. Infections in highly susceptible species may result in the death of the host plant. As of late 2013, it is infecting around 179 species in New South Wales and Queensland, from 41 genera (around 46% of genera in the Myrtaceae) in Australia....read more on Wikipedia.