Myrtle rust is a new-to-Australia fungal disease that was first diagnosed in NSW in April 2010. It affects members of the Myrtaceae family, which includes bottlebrush, eucalyptus, lillypillies, willow myrtle (Agonis spp), austromyrtus, melaleucas etc. See the list of host plants at the National Pests & Disease website. Young plants and soft new growth are most likely to be infected.
Can start with small purplish spots. Develops mature bright yellow, powdery spores on leaves and, sometimes, fruit. Leaves can become contorted and purplish-red pigmentation can occur. Soft plant material can die.