Zespri searches for new gold

MATTER OF TIME: Despite safety measures, Nelson kiwifruit growers can expect the wind-borne Psa disease to reach the region eventually, says Zespri chief executive Lain Jager.
MATTER OF TIME: Despite safety measures, Nelson kiwifruit growers can expect the wind-borne Psa disease to reach the region eventually, says Zespri chief executive Lain Jager.

The Zespri board will next month discuss whether to boost plant stocks of a gold kiwifruit cultivar showing promising tolerance to the Psa-V disease devastating orchards in the industry's heartland, the Bay of Plenty.

Chief executive Lain Jager said G3 – an early-season gold variety which has been progressively released to growers over the last few years – was showing signs it could survive Psa, but it was still too early to say it was a "credible, bankable" replacement for the main and lucrative gold variety, Hort 16A, which was being wiped out by the disease.

"There is an emerging sense that a lot of G3 is surviving Psa, especially where it is proactively managed."

At least 840 orchards – all in the Bay of Plenty – representing a third of all kiwifruit plantings nationally, have contracted the virulent form of Psa, which is killing Hort16A orchards but leaving most crops of the mainstay green hayward variety still farmable. As well as threatening the livelihoods of growers, the Psa disaster is also causing marketer Zespri and other producers to cut staff.

Mr Jager said it was inevitable that Psa would spread across the country to other major growing areas such as Kerikeri and Gisborne and also Nelson because it was borne by the wind.

Despite a huge research and development programme, no cure had yet been found to stop Psa destroying Hort16A orchards, he said.

"It's enormously important we can find a gold we can farm because that's where we make a lot of our money."

If G3 continued to show resistance over the next few months, then Zespri would be talking to growers about whether they swapped their Hort16A licences for G3, he told Nelson growers at a market briefing in Motueka on Thursday.

If it had enough confidence in G3, it was possible Zespri might provide incentives to growers, particularly those in the Bay of Plenty, to swap over.

In the meantime, the board would consider "bulking up" supplies of G3 budwood and rootstocks to enable a rapid switch when growers came to graft in June.

While G3 provided hope it represented "a commercial step on the pathway to recovery" from Psa, there were still a lot of technical issues to overcome, he said. They included whether it could be grafted on to a rootstock with Psa or required a rootstock free of infection or would be better off planted straight into the ground even though it would take longer to produce fruit.

G3 had the advantage of being a longer storing variety than Hort16A, but it was not perfect and probably was not a long-term answer because Psa was likely to mutate, he said. There were also issues getting its yields and dry matter up so it appealed to the sweeter taste preferences of Asian consumers.

There would be enough budwood available by June to replace all Hort16A but that might not be the best thing to do, particularly for those areas like Nelson which didn't have Psa, Mr Jager said. Growers in unaffected regions might be better off growing Hort16A for now, with higher prices likely next year because of a shortage of fruit.

"We will talk to growers about whether they will want to mitigate their risk by going across to G3 now or maybe continuing to farm it [Hort16A]."

He confirmed that the gold harvest was forecasted to fall from 30 million trays to 15m-17m next year largely as a result of Psa, while the green crop was projected to drop from 80m trays to 70m mainly because of seasonal factors.

Zespri was reasonably confident hayward would continue to crop well, despite suffering some vine loss and shoot die back in Psa zones, and its new, sweeter, green cultivar G14 also looked reasonably resistant. Gold variety G9 and two red cultivars appeared to be slightly more susceptible.

Mr Jager also pledged that all of next year's crop would be residue tested for the presence of antibiotic streptomycin, which is being used in the worst Psa infected areas to reduce the impact of the disease, and other chemical sprays.

Streptomycin is banned in the European Union – a major market for Zespri – because of international concerns over increasing antibiotic resistance in bacteria.

In order to protect market access, Zespri would be spending a lot of money to make sure none of its fruit had chemical residues, even though the use of such sprays was not allowed once vines had begun flowering, he said. However, it realised that some growers were desperate enough to "illegally inject their vines" so to safeguard the industry the whole crop would be "100 per cent tested".

Mr Jager praised Nelson growers for voluntarily adopting a ban on the importation of plant material and pollen in a bid to keep Psa out, but said they should expect it to eventually get here.