This serious fungal disease is well established in Australia and affects plants of the myrtle family. Unfortunately this includes some common natives like rata, pohutukawa and manuka, and since the spores could be carried here by wind a biosecurity alert has been issued to watch out for it. It can also attack fruit like feijoas and guavas.
The giveaway is bright yellow or orange powdery spots on new leaves, flowers or fruit. If you suspect it please check out this Fact Sheet (but don’t touch it because you may spread it).