Losing battle as myrtle rust found in South Island

AUCKLAND: Myrtle rust has spread to the South Island — the latest turn in what one leading ecologist has called a losing battle and a hard lesson for authorities.

The Ministry for Primary Industries (MPI) also confirmed yesterday it had given up trying to eradicate the disease and had scaled down its approach to the windborne scourge to one of longterm management.

Myrtle rust is a fungus that poses a major threat to many myrtle species plants, including New Zealand’s cherished pohutukawa, manuka, kanuka and rata.

Since it was first found in a Kerikeri nursery last year, the disease has spread to hundreds of sites across the North Island — and now to a home in Collingwood in Golden Bay and a com mercial property at Pohara.

Elsewhere, MPI has confirmed infections on five properties at Omori, on the southwestern edge of Lake Taupo, also a new region for infection.

More than 5000 myrtle plants have been securely removed and destroyed, and more than 95,000 myrtle plants inspected.

Its discovery in Nelson meant myrtle rust has been found across almost all regions identified as most vulnerable, based on habitat suitability and wind patterns.

‘‘When myrtle rust was first discovered on mainland New Zealand in May last year, we said it would be a challenging disease to contain and eradicate but we would give it a good crack,’’ MPI’s myrtle rust response spokeswoman Catherine Duthie said.

‘‘There has been an enormous operational effort over the last 11 months, but the windborne nature of the disease means that containment has not proved possible.

‘‘We have signalled for a while the likely need to change gear from intensive surveillance and the removal and destruction of host plants, to one where we look to manage the disease over the long term,’’ Dr Duthie said.

Because of the windborne, pernicious nature of the disease, there were likely to be many more infected sites beyond the more than 540 found so far.

It remained unclear what damage myrtle rust could inflict upon New Zealand’s myrtle species.

One assessment produced by the Government in 2011 warned large areas of the country could be affected and, at one extreme, some species could die on a ‘‘landscape scale’’, as had happened in other countries.

Other experts have suggested New Zealand could lose some particularly vulnerable species, such as Bartlett’s rata, particularly as they existed in the wild and because there were only a few individual plants left.

Landcare Research ecologist Andrea Byrom, who directs the New Zealand’s Biological Heritage National Science Challenge, doubted whether there had ever been any hope of defeating myrtle rust once it spread here.

‘‘Hindsight is a great thing but it really was a losing battle, partly for biological reasons — it’s a windborne pathogen, and we are going to get hit by these things more and more.

‘‘But partly, it was also for systemic reasons. There probably wasn’t a plan in place, so let’s treat this as a learning exercise.’’

Dr Byrom said biosecurity officials should now be looking at how they would stop the next big incursion, which could come in the form of rapid ohi’a death, a feared disease that has ravaged hundreds of native pohutukawa in Hawaii.

‘‘That’s the kind of thing we should be planning for and we should be doing it much more proactively than we did with myrtle rust.

‘‘To be fair to MPI, they did try. ‘‘It’s just that New Zealand, as a country, wasn’t ready. It all comes back to the fact we need to be better prepared next time.’’

It is understood there was frustration over the the myrtle rust issue among other scientists, and some questioned why a specific strategy was not put in place when the disease was first found in Australia in 2010, although MPI has stated it had long had a ‘‘well structured and rehearsed’’ system.

Dr Duthie said the focus of myrtle efforts now had to be placed on a science programme designed to lift our understanding around the disease, such as ways to treat myrtle rust, resistance and susceptibility, and to improve seed banking collection.

‘‘A second key focus has to be on working with communities across New Zealand to support regional efforts to combat myrtle rust,’’ she said.

‘‘MPI and Doc will be engaging with iwi and hapu, territorial authorities, the plant and nursery industries, and communities. — NZME

❛ There probably wasn’t a plan in place, so let’s treat

this as a learning exercise