A new contagious fungal plant disease has entered Australia, myrtle rust. It's highly mobile, can reproduce rapidly and is infecting many species across a broad geographic range. Containment and eradication responses have so far been unsuccessful. In short, the risks posed by myrtle rust are a perfect storm for plant species within one of Australia's most important plant families, the Myrtaceae. Jarrah Wills from the Queensland Herbarium describes why this plant disease poses such a threat and what we are doing about it.