Psa – new strains (kiwifruit vine canker)

Pseudomonas syringae pv. actinidiae

Psa is one of the most serious diseases of kiwifruit. We have one variety of Psa present in New Zealand. There are other strains that we're trying to keep out.

About Psa (kiwifruit vine canker)

Psa is damaging kiwifruit industries throughout the world. Thousands of hectares of orchards have been destroyed, especially of gold kiwifruit. The disease became a worldwide problem in only a few years and it is still spreading.

In New Zealand, the kiwifruit industry has largely recovered, due to the planting of gold kiwifruit varieties that are resistant to the strains of Psa present here.

Global distribution of Psa

World map showing Psa distribution

Why we're concerned

Psa is one of the most important diseases of kiwifruit. It causes bacterial canker of green and gold kiwifruit, and kiwiberry.

If new strains of Psa come into New Zealand from other parts of the world, they could cause further losses.

How could it get here?

While one type of Psa (biovar 3) is already here, we want to keep other types out. They could get here on infected planting material. MPI has strict measures in place to limit the chances of them making it through the border.

How to identify Psa

Psa infections can cause:

  • leaf blotches with straight edges
  • leaf and plant wilting
  • twig and cane dieback and cracking
  • cankers (lesions) on canes, leaders, and trunks
  • red or white ooze to form on the undersides of leaves, canes, buds, joints of branches, forks, leaf scars, and pruning scars
  • infected flowers to turn brown and wither without opening
  • affected fruit to be small and misshapen
  • fruit to collapse because the branch has wilted and the fruit is not getting the fluid it needs.
tree trunk with red ooze under a lesion or pruning scar
Psa can cause a red ooze to form. 

What to do if you think you've found Psa

If you are an orchardist and disease symptoms are worse, different, or unexpected from current Psa symptoms:

 


Note: This information is a summary of Psa's global distribution and potential impacts to New Zealand.

Last reviewed:
Has this been useful? Give us your feedback