What does it look like?

The highly virulent bacterium Pseudomonas syringae pv. actinidiae (Psa) causes bacterial canker on kiwifruit vines. This bacteria is found in several countries worldwide, including Italy, Chile and Japan, and was first identified in New Zealand in 2010. Currently, Psa affects 80% of the kiwifruit growing areas in New Zealand.

Why is it a problem?

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. For a detailed identification guide visit www.kvh.org.nz/vdb/document/870.

Control Methods

To ensure the on-going containment of the kiwifruit vine disease Psa-V, all farmers must consider the risk of spreading Psa-V by the movement of contaminated plant/leaf material associated with reject fruit loads for animal feed. As these loads have the potential to harbour infected leaf/plant material Northland growers are preventing all inter-regional movements of reject fruit consignments as these can provide a pathway for the entry and establishment of Psa-V in Northland.

For orchard management options visit www.kvh.org.nz/orchard_management.