Psa (bacterial kiwifruit vine disease)
Pseudomonas syringae pv actinidiae
Psa (bacterial kiwifruit vine disease)
Psa was first detected in New Zealand in the Bay of Plenty (Te Puke) in November 2010. Since then the disease has spread widely throughout the Bay of Plenty and is now also present (11 October 2012) in Waikato, Franklin District and Coromandel. The number of Psa positive orchards is now over 1600 and 57% of the hectares on kiwifruit orchards now contain at least some infected vines.
In the early stages of the disease outbreak, Government contributed $25 million, matched dollar for dollar by industry, for the management of Psa.
MPI continues to support the industry with its research and management of the disease. Day to day management activities are run by Kiwifruit Vine Health (KVH).
KVH has the latest and most comprehensive information about Psa spread and management at: www.kvh.org.nz
You can also call KVH on 0800 665 825
General Information about Psa:
Pseudomonas syringae pv. actinidiae (Psa) is a bacterium that can result in the death of kiwifruit vines. Psa carries no risks associated with human or animal health and does not affect plants other than kiwifruit vines.
Growth of the bacteria outside/inside the vines can result in leaf spotting, cane/leader dieback and, in extreme cases, vine death accompanied by the production of exudates (a rusty red liquid discharge).
Psa was first identified in Japan in the 1980s where the disease caused damage in kiwifruit orchards. It has since also been identified in Korea.
The disease was first noticed in Northern Italy in 1992 where it remained sporadic and with a low incidence for around fifteen years. In 2007/2008 economic losses started to be observed particularly in the Lazio region and the possible spread of the disease, to other kiwifruit producing regions in Italy, began to cause concern. Psa is continuing to emerge in the Mediterranean region where the European & Mediterranean Plant Protection Organisation (EPPO) Secretariat has included the disease to the EPPO Alert List.
Symptoms are usually expressed during spring and autumn when climatic conditions are favourable – i.e. cool temperatures, persistent rains and high humidity. Psa is temperature sensitive and active between 10 to 20 degrees but limited by temperatures over 25 degrees. The disease can be spread via windborne pollen, strong winds and heavy rainfalls. It is also believed to be spread by footwear, vehicles and orchard tools, animals and humans. The bacterium infects the plant through natural openings (stomata and leaf axis) and wounds.
Symptoms include angular shaped spots, often associated with a halo, although not all leaf spots clearly exhibit the halo, brown discolouration of buds and, in advanced stages of infection, the leakage of red-rusty gum. Not all symptoms appear at the same time.
MPI investigations and reviews
How Psa may have entered New Zealand
From the outset of the response to Psa, MPI (and formerly MAF) has investigated a range of potential pathways for how it was introduced - these include scientific trials, pollen, pollen application equipment, imported plant material, and people movements. A summary of this research was compiled into a report (known widely as the pathway tracing report). This report was finalised on 5 December 2011.
The report does not identify a single likely pathway. It finds that there is low likelihood of most of the pathways examined being the entry route, but does identify pollen and people movements as possible pathways. Neither can be concluded as the definite means of entry.
- Psa - Pathway tracing report. December 2011. A summary of MAF's investigations into potential entry pathways for Psa (191 KB)
Independent review of import requirements and border processes associated with imports of kiwifruit plant material
This review by Sapere Research Limited was commissioned in February 2012 by Director-General Wayne McNee.
Below are links to the independent review, MPI's media release, the MPI Management Action Plan, a video of the press conference on 4 July 2012 and a progress report on the Management Action Plan.
- Progress report on MPI Management Action Plan - 31 August 2012 (209 KB)
- Psa-V review 2012 (986 KB)
- MPI Management Action Plan in Response to Kiwifruit IHS Independent Review (2364 KB)
- Press Conference for Release of Psa Review - 4 July 2012
Psa-V Primary Sector Recovery Declaration
The Minister for Primary Industries declared Psa-V affecting North Island kiwifruit growers as a medium-scale biosecurity event under the Government’s Primary Sector Recovery Policy in December 2012.
The declaration means the Government will fund provision of services to help affected growers deal with the impacts of the incursion, and the hardest hit growers could be eligible for payments.
Full and current information about Psa in New Zealand is at www.kvh.org.nz or call KVH on 0800 665 825.
Page last updated: 12 November 2015