The disease can kill feijoa, pohutukawa, manuka, gum and bottlebrush.
Horizons plant biosecurity leader Craig Davey said since Thursday one person had also brought a plant suspected to have the disease to the council office. It was a hydrangea — not susceptible to myrtle rust.
He said the Central Plateau was warm and wet enough for the rust to prosper. It was best not to touch infected plants because the disease transferred so easily.
He said it was important to keep tracking the disease in order to understand how it behaved in New Zealand.
Ramarama might be particularly susceptible to myrtle rust, or it might be most often found on ramarama because the shrubs are smaller and its easier to see.
The Whanganui plants have been double-bagged for disposal in a landfill, where they must be buried between 10cm and 15cm deep. Their roots were poisoned to stop regrowth, and the area was sprayed with fungicide.
Davey said it was an expensive process, and it is one which is still happening in Australia, where the disease has been established for longer.
"Every tree that's bagged is a whole lot of innoculin taken out of the system."
In Whanganui, every plant within 500 metres of the infection was checked for signs of the disease, and that will happen again in 10 days' time.
The Ministry for Primary Industries and Department of Conservation are also involved in myrtle rust surveillance and removal. Whanganui DoC staff have been upskilled in spotting and containing it, and have indicator locations.
They have helped to destroy infected plants in several places during the last 11 months, a spokeswoman said. They have also been collecting the seed of healthy plants, as part of a national effort.
*Anyone who suspects they have seen myrtle rust is asked to ring 0800 80 99 66, and to take a photograph if possible, without touching it.
