Infected kiwifruit vines may need to be burned - Zespri

A kiwifruit vine. File photo / Alan Gibson

One option for containing the vine-killing bacteria found on a Bay of Plenty kiwifruit orchard may be to rip out the infected vines and burn them.

The bacteria - named Pseudomonas syringae pv. actinidiae but best known as PSA - was last night confirmed for the first time to have infected New Zealand kiwifruit vines.

The strain of bacteria in New Zealand has not yet been identified, but the one which caused the worst damage in Italy particularly affected gold cultivars - including Zespri's lucrative Hort16A.

Gold kiwifruit are the most profitable cultivar in New Zealand, making up 77,000 tonnes or 21 per cent of Zespri's production last season, but about 34 per cent of the crop's earnings: $285.7 million.

Zespri is working closely with scientists and research partners to determine the most effective and appropriate control mechanism, which it says will partly be directed by the geographical location, proximity to other orchards and the site's risk profile.

A spokeswoman said that control strategies "may take into consideration the need to remove and destroy the infected vines".

But Zespri chief executive Lain Jager was more blunt when asked if the industry might seek to have the infected vines destroyed.

"If it looks like this thing is containable, I imagine that MAF would take a leadership position," he said. "In this case, that would probably involve cutting and burning".

"I can't speak for MAF, but from an industry perspective, we would be working very closely with MAF to determine how that could be achieved".

Mr Jager acknowledged a New Zealander with direct experience of the Italian disaster, Opotiki Packing and Coolstorage Ltd (Opac) managing director Craig Thompson, had said that the Italians had wrongly thought that normal measures such as removing and burning infected vines would get the outbreak under control.

"The severity of this outbreak is such that (that) hasn't been sufficient to control it," Mr Thompson said in April after the disease gutted the company's million-tray 84ha Newgold orchard in Italy's Lazio region, and the company's directors warned that their $7 million investment should be written off.

Japanese efforts to use copper compounds and antibiotics against the disease led to the evolution of resistant bacteria, but Mr Jager said experts said copper could be used in New Zealand to slow down the bacteria.

"Eventually this thing will settle down to where either we've eradicated it or there's a mature management regime, but in the meantime people will be thinking very hard about how to minimise their exposure," Mr Jager said.

It was important to understand New Zealand conditions were not the same as in Italy, without a tremendously cold winter and there was no sign of cankers yet on the NZ vines.

"There are other strains of PSA in Japan and Korea and they manage it quite well," he said. "Where they have an infected vine, the orchardists cut it out and move on."

"We are at the beginning of an enormous learning curve".

Best-practice protocols yet to be developed for New Zealand might include copper foliar sprays, experimentation with antibiotics, and cutting and burning.

- NZPA