West's kiwifruit growers on Psa alert

21:13, Feb 18 2013
FIONA MCRAE: With no easy solution to Psa-V on the horizon kiwifruit growers want not just orchard visitors but everyone in the industry to take care.

Kiwifruit growers in the west are asking the public, Auckland Council and other industry members to be vigilant to keep Psa-V out of their orchards.

The disease, which attacks kiwifruit vines but is not harmful to humans, has devastated the $1 billion industry since it was first identified in New Zealand on a Te Puke orchard in November 2010.

Three-quarters of New Zealand's kiwifruit-producing hectares have been confirmed with Psa-V, although the South Island is still free of it.

Last year the 27 orchards in the northwest, 48 orchards around the Whangarei area and 103 around Kerikeri were still disease-free but an orchard in Kerikeri has now shown positive, New Zealand Kiwifruit Growers president Neil Trebilco says.

"The disease can be spread by weather events, especially wind-driven rain.

"This year's dry summer has helped limit the spread of the disease but Psa-V progression will start moving again once autumn arrives, as the bacteria thrive in cooler and wetter weather conditions," Kumeu kiwifruit orchadist Fiona McRae says.


The industry is still grappling with how to deal with the disease, which affects all the kiwifruit varieties grown commercially. The gold 16A variety is the worst affected and Hayward the least, Mr Trebilco says.

The Kiwifruit Vine Health group, of which Ms McRae is a member, has developed a National Management Plan for Psa-V. This was submitted to the Ministry for Primary Industries in October and they hope the ministry will back it.

The plan includes enabling unmanaged and abandoned orchards to be controlled so they do not present an unacceptable risk to other orchards.

Meanwhile, more than $10 million has been invested in the KVH/Zespri Psa R&D programme.

More than 300 horticultural products have been trialled, with copper sprays similar to those used on apples for blight, showing some success.

Changing management practices to reduce vine cutting, which allows the disease to get into the plant, has also had some success.

But Zespri general manager science and innovation Dr David Tanner says developing new resistant cultivars, the best solution, could still be 10 years away.

Four cultivars are in trials and likely to be ready for commercial release from next year to 2015, if they prove to have the necessary Psa and commercial qualities.

But because they were all bred well in advance of Psa's arrival in New Zealand, the chances of finding a Psa-tolerant cultivar among them, are low, he says.

At the next level, there are 200 cultivars in clonal trials and being tested for Psa tolerance.

It may not happen quickly but there is a good chance of finding Psa-tolerant cultivars, he says.

Trebilco says that, internationally, whoever comes up with a Psa-tolerant cultivar first will have a huge commercial advantage.

With the amount of research here that could well be us, he says.

Ms McRae says: "A collective approach is essential for growers and the wider industry, including post-harvest operators, such as pack houses and trucking contractors, to ensure everything possible is being done to protect the northwest from Psa-V." New Zealand is the biggest exporter of kiwifruit internationally, followed by Italy and then Chile. Italian growers were hit several years before New Zealand and many of their Gold 16A variety vines have now been removed.

Rodney Times