Tools for managing the kiwifruit bacterial canker disease Pseudomonas syringae pv actinidiae (Psa)

Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of bacterial canker in kiwifruit. The speed of the spread of the bacteria and the devastating impact on kiwifruit vines, particularly 'Hort 16N, has resulted in an extensive research program to identify chemical and biological control agents which can be used to manage the disease. Antibiotics and copper products have been shown to be very effective in the control of Psa, and other bacterial diseases in other crops. Elicitors, which induce the plant immune response, have also shown promise in the fight against bacterial plant diseases. In addition, biological agents such as beneficial bacteria, can compete with the bacterial pathogen, or produce antimicrobials which destroy the pathogen directly. However, resistance and tolerance have developed in other bacterial diseases towards antibiotics and copper respectively, which poses a potential problem in the control of Psa. Phytotoxicity and residues also pose a problem with continued or overuse. In addition, there are restrictions on use both in terms of the region where a product can be used and number of times when a product can be sprayed. Thus, it is imperative to identify a number of alternative control agents. The development of a product 'toolbox' for the management of Psa has been an ongoing process. The range of products identified as having efficacy against Psa, the uses and limitations are discussed.