Peters dismisses 'out of Australia' theory as fungus spreads

MPI staff examine plants at Kerikeri Plant Production a day after myrtle rust was first discovered on the New Zealand mainland. PHOTO / Peter de Graaf

Northland MP Winston Peters says the fact all five cases of myrtle rust found so far have been in or next to plant nurseries casts doubt on the theory the plant disease arrived on the wind from Australia.

The fungus was originally found in a Kerikeri plant nursery on May 2, sparking a major biosecurity response, and a few days later in a neighbouring garden. On May 16 it was also found in a plant nursery in Waitara, Taranaki, and on May 19 in a second nursery in Waitara and a garden centre in downtown New Plymouth.

The Ministry for Primary Industries (MPI) said there was no known link between the Kerikeri and Taranaki nurseries.

If the disease becomes established it could threaten natives such as pohutukawa, rata and manuka, as well as garden plants such feijoa and bottle brush.

Mr Peters said the odds of wind-blown fungus spores from Australia landing on nurseries 600km apart were "astronomical", and it was more likely the fungus had reached New Zealand through a "catastrophic failure of biosecurity".

The NZ First leader said a myrtle rust briefing by the Crown research institute Scion in 2010, when the disease first reached Australia, put the risk of it blowing across the Tasman as low. Scion said it was more likely that spores would enter New Zealand on clothing or footwear, deliberately, or on imported plant material.

The fact that all finds so far were in or next to plant nurseries pointed to the latter, Mr Peters said.

He also questioned how officials could be so certain the spores had arrived from Australia when the disease was also established in New Caledonia and, as of March, Raoul Island, which is much nearer New Zealand.

MPI's myrtle rust response incident controller David Yard said, however, there were reasons the disease had first come to light in nurseries.

Growing conditions in nurseries were ideal for the fungus with many vulnerable young plants in sheltered, warm and damp environments, and nurseries had been vigilant about checking their plants.

"While we are unlikely to ever know exactly how myrtle rust arrived in New Zealand, the most likely entry route remains being carried here on the wind from Australia where the infection is widespread," Mr Yard said.

"Plant matter is a very unlikely means of entry as there are tight restrictions on the importation of any myrtle species plant material from Australia."

About 20 weather events a year were capable of carrying the spores across the Tasman.

The new finds were "disappointing but not unexpected", he said.

Meanwhile, MPI staff are spraying the Taranaki sites with fungicide and inspecting all properties within 500m.

In Kerikeri field staff have completed a second round of inspections in a 500m radius from the original nursery without finding any more infected plants. All plants that could be affected by myrtle rust have been removed from the nursery and destroyed.