Psa of kiwifruit: Declared pest

Page last updated: Friday, 7 February 2020 - 4:07pm

Psa (Pseudomonas syringae pv. actinidiae) is a disease of kiwifruit that can spread rapidly through kiwifruit orchards and kill many vines. This pest is not known to occur in Western Australia. Early detection and reporting of Psa will help protect the Western Australian kiwifruit industry.

What plants are affected?      

Psa is a bacterial disease that affects kiwifruit and kiwiberry vines. It carries no risk to humans.  

What do I look for? 

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White slime oozing out of an infected vine
  • Dark spots with yellow haloes appear on the leaves of kiwifruit in spring.
  • Multiple leaf spots may join together and make the leaves drop.
  • Buds and flowers may rot.
  • Symptoms on the vine include stem cracking, cankers, wilt, dieback and cane death.
  • Orange and white bacterial ooze appears on the bark of twigs and trunks.
  • The gold kiwifruit variety Hort16a is very susceptible to Psa. The green Hayward variety is less susceptible.

There are several strains of Psa that can kill kiwifruit vines, including Psa1, Psa2, Psa3 and Psa5. A bacteria that is related to Psa is already present in Western Australia. It is called Pseudomonas syringae pv. actinidifoliorum (Psaf). Psaf can cause dark spots on the leaves of kiwifruit, but does not cause vine dieback.

How does the disease survive and spread? 

  • The bacteria are spread from plant to plant by wind and rain in the spring.
  • Hot dry weather greatly reduces the survival of Psa.
  • Psa is also spread on infected plant material, in kiwifruit pollen, on tools such as secateurs, and on footwear and vehicles.
  • Psa survives in fallen leaves and pruning debris, on the surface of kiwifruit leaves and stems and in flower and leaf buds.

What damage can this pest cause? 

Psa has destroyed kiwifruit orchards in many parts of the world, and would cause heavy losses for kiwifruit growers in Western Australia.

Status in Western Australia 

Pseudomonas syringae pv. actinidiae Takikawa et al. 1989 Biovars 1, 2, 3 and 5 are absent from Western Australia and are quarantine pests. They are prohibited organisms under section 12 of the Biosecurity and Agriculture Management Act 2007.

Western Australia's Pest Freedom for Psa is supported by general and specific surveillance and specific import requirements to prevent its entry. A person who finds or suspects the presence of Psa must report it.

Report suspect disease

Early detection and eradication will help protect Western Australian kiwifruit growers. Please make a report on MyPestGuide or contact the Pest and Disease Information Service (PaDIS) to report this pest.

Report your observations using the MyPestGuide Reporter app or online at mypestguide.agric.wa.gov.au.