PSA-V

Psa-V Pseudomonas syringae pv. actinidiae (Psa) is a bacteria that can result in the death of kiwifruit vines. It was first discovered in New Zealand in November 2010 and rapidly caused widespread and severe impacts to New Zealand's kiwifruit industry.


Pseudomonas syringae pv. actinidiae (Psa) carries no risks associated with human or animal health and does not affect plants other than kiwifruit vines. Psa is believed to be spread by weather events, namely wind and rain, and plant material. It is also believed to be spread by footwear, vehicles and orchard tools. In an orchard it can exist as:

  • an epiphyte, living on plant surfaces without causing high levels of infection; and/or

  • as an endophyte, living within the vine, having entered through natural plant openings or man made wounds - resulting in severe infection.

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. Click here for a Psa-V Symptoms Guide.

Since its discovery in 2010 a significant amount of funding and resource has gone into a Psa-V research and development programme to better understand and manage the disease.

Based on the results of this programme, and on-orchard experience, KVH has developed a series of best practice resources to assist growers with managing the disease.

Different outbreaks of Psa have been caused by five related, but genetically distinct lineages of Pseudomonas syringae and it is likely that many more exist in wild kiwifruit populations.

Psa1 (Japan, Italy) and Psa2 (Korea), are of particular concern as these strains are more virulent against Hayward cultivars than the Psa-V strain currently in New Zealand.

New genetic material of any strain is a concern due to the potential of horizontal gene transfer and the impact new strains may have on new or existing kiwifruit cultivars.

New strains of Psa are also expected to evolve within New Zealand, of which the characteristics and virulence to new and existing kiwifruit cultivars are unknown. Good biosecurity practices are vital to prevent the spread of any new strains between orchards and growing regions.

Biovar
Countries
Virulence
1

Japan, Italy

High virulence, especially to Hayward cultivars

2

Korea

High virulence, especially to Hayward cultivars

3

(Psa-V)

Italy, Chile,

China, NZ,

France, Portugal,

Japan, Korea

High virulence, especially to Hort16A cultivars

Less virulent on Hayward than Psa1 & Psa2

4

NZ, Australia

Low virulence

5

Japan

Low virulence

Psa was first identified in New Zealand in November 2020, and what followed was one of the most tumultuous times in the history of the New Zealand kiwifruit industry. In honour of this anniversary KVH has commissioned a project which captures some of the stories from the early days of Psa. While many growers would prefer to forget these harrowing days, capturing these stories and the lessons from our past experiences is important to improve our preparedness for future incursions and share these lessons with others.

Read here the tales from the April 2021 special book release of reflections from the kiwifruit industry’s biggest biosecurity response and recovery. We are extremely grateful for the generous sponsorship and support from the many organisations that contributed to the production of the booklet, and those who have been willing to share their stories.