21 Sep 2012

More PSA discovered in kiwifruit vines

1:53 pm on 21 September 2012

The Kiwifruit Vine Health organisation says there have been 55 new notifications this week of orchards with the vine-killing disease PSA.

At least 1420 orchards in Bay of Plenty, Waikato, Coromandel and South Auckland now have the disease.

Exactly a year ago, only 295 orchards, all in Bay of Plenty, had been confirmed as having the virulent strain PSA-V.

New Zealand's largest kiwifruit grower, Seeka, says sap movement as vines come out of their dormant winter phase has resulted in more symptoms being found in its orchards.

Michael Franks, chief executive of the Te Puke-based grower, says in spring last year it was mainly the gold variety Hort 16A which was hit by the bacterial disease, but this year nothing seems immune.

He says there are widespread exudates or cankers on the male plants and there are also some Hayward green female kiwifruit showing serious signs of the disease.

Mr Franks says balancing that there is now a good spring bud burst.

"We just fought off a big frost last week and the young grafts where we cut orchards off at the stumps and then we've grafted new varieties onto those stumps ... and those young grafts are all quite tender at the moment so we're watching those quite carefully."

Mr Franks says protective plastic sleeves placed around the graft have helped warm them during the day but then act as a cold trap when the temperature drops at night.

Meanwhile, Kiwifruit Vine Health is working hard to process applications from growers who want to use the bacteriocide streptomycin on their vines in an effort to reduce the chance of infection.

So far staff have undertaken audits of 260 orchards, including Seeka.

Seeka chief executive Michael Franks says streptomycin was a key part of its PSA management last year and will be again this spring.