As the results of testing across the country begin to roll in this week, New Zealand’s kiwifruit industry is trying to establish whether the outbreak of kiwifruit canker confirmed on Monday can be eradicated or contained, or must simply be managed.
The path taken to deal with the outbreak will be based on how widespread the Pseudomonas syringae pv Actinidiae (Psa) infection is determined to be.
Infections have been confirmed in three orchards in Te Puke in the Bay of Plenty region as of 1pm today New Zealand time, with five orchards in total under quarantine.
Those five orchards are all within the same 10km-wide area, and add up to about 100ha of the Hort16a gold variety.
While those figures have not advanced since yesterday, single-desk marketer Zespri said the number of confirmed infections could rise as more test results come in.
“In the next 48 hours there may be a lot more orchards with Psa confirmed on them,” Zespri CEO Lain Jager said during a conference call today.
By Friday, Zespri expects to have bacterial DNA testing results in for nine orchards, rising to 40 by Saturday and 70 by Sunday.
Determining the spread
In an effort to establish the spread of the disease, New Zealand’s Ministry of Agriculture and Forestry (MAF) and Zespri are today deploying a team of 40 specialists to collect random leaf samples from gold and green orchards.
That testing will initially focus in the Te Puke area around the confirmed infection sites, before extending around the country.
Growers have been sending in photos to Zespri of suspected Psa symptoms since the confirmation of the initial infection. According to the latest figures, 135 growers have contacted Zespri, 78 with potential symptoms and 57 with the all clear.
While those numbers may initially appear concerning, many of those potential identifications will likely turn out to be innocent on closer inspection.
“This is a new thing for orchardists to be looking for,” said Barry O’Neill, director general of MAF agency Biosecurity New Zealand. “In a number of orchards that have sent us pictures we probably will be able to rule them out.”
“And of course PSF `Pseudomonas savastanoi fraxini` is a very similar bacterial problem and has been around for years, and looks very similar,” added Mr Jager.
He said Zespri and MAF would be prioritising testing in areas outside the Bay of Plenty to determine if the bacteria had spread that far. As the results of that testing come in, Mr Jager said the industry would be able to develop an informed action plan.
Three options are currently on the table; eradication, if the infection is sufficiently limited in scope; containment, if it is too widespread to eradicate but still limited to specific regions; and management, if the infection is present across the whole country.
“Everyone understands that our first priority is to eradicate Psa from New Zealand,” stated Mr Jager. “If we can’t eradicate it, the tactic is to contain it or exclude it from some parts of the country. We’re looking outside the Bay of Plenty to other growing areas; if it’s in other areas, it has reduced the rationale for containment.”
Avenue of infection
The big question at this stage is how and when the infection entered New Zealand.
There is some suspicion in the industry that Psa has been present in the country for a number of years, but lying dormant until the cold, wet conditions of this year’s winter increased kiwifruit vine stress and allowed the disease to express itself, as happened in Italy last winter.
“As we sit here today, we don’t know if Psa has been here three or four years; maybe it’s been dormant, or maybe it’s just arrived,” said Mr Jager. “There’s a lot of discussion about that because it’s very relevant to the industry’s perception of what the best way to manage this is.
“If it’s been here and vines have been coping with it, and it’s just the climate `that’s brought it out`, then that leads you done one path of thinking how to manage this thing. Then of course if it’s just arrived we don’t know how it’s going to behave in New Zealand.”
Efforts to backtrack the entry of the disease have so far turned up no solid results. Authorities say they have not been able to identify any lapse in New Zealand’s biosecurity system that could have enabled the infection, and the growers with confirmed infections do not appear to have been at fault either.
“We can find no evidence that the orchards that we’ve got biosecurity control restrictions on have done anything different or anything that could have resulted in the introduction of the disease,” said Mr O’Neill.
Export impacts
The effect on New Zealand’s kiwifruit exports so far has been mild. The international scientific consensus appears to be that kiwifruit canker cannot be transported on mature fruit, meaning export markets have no technical grounds to suspend New Zealand access. That was no guarantee others would take the same view, cautioned Mr Jager in an earlier address to growers.
“We have had no country put in a restriction to the import of New Zealand kiwifruit,” explained Mr O’Neill.
“In fact we have had a positive confirmation from Australia yesterday that their assessment was, as our assessment is, that kiwifruit does not present a risk. And we’ve also had confirmation from both the US and Japan that they are not taking any action against New Zealand fruit.”
Australia and the US have both suspended access to New Zealand kiwifruit nursery stock, a move that Mr O’Neill describes as quite reasonable.
Response speed
With the infection initially suspected on Friday and confirmed as Psa on Monday, the speed of the New Zealand kiwifruit industry reaction to the canker outbreak has been impressive.
Key figures claim that rapid response is a result of the kiwifruit industry’s unity and familiarity with coordinated action.
“We are all banding together, we have a cohesive industry that can get together and fight this. If we do that, if we act responsibly but quickly we may well be able to get on top of this,” said David Tanner, Zespri’s head of global technical and innovation.
Despite the headlong speed, Mr Jager emphasised Zespri and MAF were pausing to consider key aspects, such as the use of copper sprays to control bacterial spread.
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