Kiwifruit and Psa – a timeline

This timeline follows the discovery of the bacterial disease Psa (Pseudomonas syringae pv. Actinidiae) in New Zealand, the combined efforts to first contain and manage the disease and the research that enabled the kiwifruit industry to make a strong recovery. Find out how this work reflects the nature of science. A full transcript is underneath the timeline.

Transcript

Chronology of events

A brief sequence of events to first contain then find ways to minimise the impact of Psa-V.

Nature of science

A reflection of how science and scientists work.

CHRONOLOGY OF EVENTS

1984 – Psa in Japan

Psa symptoms first appear on green kiwifruit growing in Japan.

Image: Symptoms of PSA infection on Kiwifruit, Kiwifruit Vine Health (KVH)

1992 – Psa in Italy

Psa is identified in kiwifruit orchards in northern Italy. Outbreaks remain sporadic for several years.

2008 – Italian kiwifruit industry decimated

In 2007/08, conditions are ideal for the spread of Psa. Kiwifruit in the region of Lazio are decimated, including a New Zealand-owned orchard. Cost estimates for the Italian outbreak are €2 million (NZ$3.5 million).

5 November 2010 – Psa detected in New Zealand

Psa is first detected on a Te Puke orchard. Technical experts from the Ministry of Agriculture and Forestry, Plant & Food Research and Zespri visit the area to confirm the disease. The orchard is quarantined.

Image: Diseased kiwifruit. University of Waikato

11 November 2010 – 75 orchards showing possible symptoms

The Ministry of Agriculture and Forestry begins to check other kiwifruit-growing regions for Psa symptoms. Scientists complete tests to determine what strain of Psa is present. Testing eventually shows that New Zealand has two strains: biovar 3 (highly virulent Psa-V, especially to Hort16A cultivar) and biovar 4 (less virulent Psa-LV).

18 November 2010 – South Island cases confirmed

Motueka and Golden Bay confirm cases of Psa. Experts suspect that Psa has been in the country for some time, but a severe weather event stressed vines, allowing the disease to take hold.

23 November 2010 – Containment strategies

Industry, government and science agencies try several strategies to contain the disease. Infected vine cuttings are destroyed in huge incinerators or by burial in deep pits. Copper sprays and other chemical solutions are trialled. Movement between orchards is controlled, and equipment is disinfected.

Image: When filming at a kiwifruit orchard the Science Learning Hub crew had to wear protective clothing to reduce the risk of PSA spread. University of Waikato.

December 2010 – Kiwifruit Vine Health is established

Kiwifruit Vine Health (KVH) is established to lead the industry response to Psa-V. KVH holds numerous research and development update meetings featuring the latest scientific and industry information.

October 2011 – Psa-V spreads in New Zealand

Psa-V is now identified in 369 orchards covering 2,214 hectares.

May 2012 – Significant funding for investigations

Plant & Food Research (PFR) has a large team of 100+ people working on the development of Psa-tolerant and resistant cultivars. PFR, Zespri and Kiwifruit Vine Health invest more than $11.5 million in research.

May 2012 – Gold3 identified as Psa tolerant

Gold3, growing in a PFR research orchard, appears to be tolerant to Psa-V. Plant & Food Research fast-tracks commercialisation. More than 2,000 ha of Gold3 plants are released to growers.

Image: Zespri® SunGold kiwifruit. University of Waikato

July 2012 – More orchards are infected

12,000+ New Zealand kiwifruit orchards are infected with the virulent form Psa-V – nearly 40% of the country’s orchards.

May 2013 – National Psa-V Pest Management Plan

Minister for Primary Industries Nathan Guy approves a National Psa-V Pest Management Plan (NPMP). The plan ensures the entire industry works together to overcome the impacts of Psa-V. Grower levies fund the NPMP.

July 2013 – Psa bacteria origins

An international collaboration discovers that a single source of the Psa bacterium is responsible for the recent outbreaks of Psa in New Zealand, Italy, Japan and Korea. They report that the Psa bacterium most likely has its origins in Asia. However, the Psa-V strain is a much more recent offshoot.

Image: Micrograph of PSA bacteria, Plant & Food Research

November 2014 – Crowdsourcing knowledge

Plant & Food Research scientists share kiwifruit and Psa bacterium genome sequences for global collaboration. They invite the international science community to help solve the problems facing kiwifruit growers across the world.

May 2015 – Biocontrol microorganisms

A consortium of New Zealand experts investigate biological control agents (BCAs) that can significantly resist Psa symptoms in kiwifruit vines. Two BCAs are applied to the leaves. One BCA is a root-dwelling beneficial fungus.

April 2016 – Partnering with China

New Zealand scientists partner with China to identify new sources of resistance to kiwifruit pests and diseases. Research leader Dr Mirco Montefiori notes, “We have a large kiwifruit germplasm collection in New Zealand, but the diversity of kiwifruit vines in China is virtually endless.”

Image: Plant & Food Research

June 2017 – From $2.6 billion to $6.14 billion

The kiwifruit industry continues to recover. A University of Waikato report suggests the kiwifruit industry will increase its contribution to New Zealand’s GDP from $2.16 billion in 2015/16 to $6.14 billion in 2030.

February 2018 – Prime Minister’s Science Prize

Plant & Food Research receives the 2018 Prime Minister’s Science Prize and will use the $400,000 prize to support bioprotection technologies.

Image: Prime Minister Jacinda Ardern with Dr Bruce Campbell, Plant & Food Research Psa Team Leader. Prime Minister’s Science Prizes Secretariat

April 2018 – Living with Psa-V

Kiwifruit Vine Health reports that 2,949 orchards are identified as having Psa-V. This represents 92% of New Zealand’s kiwifruit hectares. Growers live with Psa but have a toolbox for managing the disease.

June 2018 – High Court rules in favour of kiwifruit growers

The New Zealand High Court rules that the Ministry of Agriculture and Forestry – now known as the Ministry for Primary Industries – breached its duty of care by approving a permit to import pollen products into New Zealand. The Crown argues that growers do not have a case as studies regarding how Psa-V entered the country are inconclusive.

Image: Rafael Ben-Ari, 123RF Ltd

NATURE OF SCIENCE

5 November 2010 – Need for evidence

Collecting data is integral to scientific research. Experts visit orchards to collect samples in order to identify the disease affecting the kiwifruit vines. The data (evidence) confirms it is Psa.

11 November 2010 – Data is not always straightforward

Initial data was confusing as it appeared that Psa has spread all over the country. Scientists have to analyse and interpret the data to explain why the disease is in so many areas.

23 November 2010 – Using prior evidence

Science and industry use existing information to try and prevent the spread of the disease. Science knowledge often represents the best explanation at the time but can be revised if warranted by new evidence.

December 2010 – Shared purpose

Scientific investigations often bring people from a range of experiences together. Industry and science join together to share information and keep the public informed.

May 2012 – Society and science funding

Science exists within and is influenced by the needs of society. Primary industries like horticulture are valuable to the New Zealand economy. Societal needs often influence where and how science funds are allocated.

May 2012 – Making predictions

In science, a prediction is an expectation that a hypothesis is correct. Scientists usually prefer to have sufficient evidence to support a hypothesis, but some situations require more urgent action.

26 July 2013 – Building knowledge

Scientists seek to build knowledge about the natural world. Researchers from New Zealand, Germany, Switzerland and Canada combine new molecular knowledge with existing knowledge to develop long-term solutions for Psa-resistant cultivars.

November 2014 – Collaboration and sharing ideas

Scientists rarely work alone. Most research takes too long, is too expensive and needs more knowledge and expertise than one person or even a small team may have.

May 2015 – Tentative nature of science

Working on multiple solutions offers opportunities for trial and error. Ideas may fail before more successful measures are discovered. This is an important part of the research process. The scientific process presents both challenges and promising results.

April 2016 – Scientific research is an ongoing activity

Most scientific research is rarely considered ‘finished’. Even though Psa appears to be manageable in New Zealand, scientists continue to look for answers.

February 2018 – Contributing to society

Science has significant impact on our physical, social, economic and environmental health and wellbeing – as demonstrated by the rapid and effective response of the Plant & Food Research team to the Psa crisis.

June 2018 – Science is a knowledge system

Although scientific research is used as evidence in legal matters, science itself is a knowledge system. Research provides information, which is then acted on by other parties.