A new management tool is being sought for a bacterial disease which has caused significant losses for tomato growers and for which there are few, if any, existing controls.
The A Lighter Touch-TomatoesNZ project will evaluate the efficacy of the biological product Aureo GoldTM, used for managing Psa in kiwifruit, against bacterial canker in tomatoes, which is caused by Clavibacter michiganensis subsp. michiganensis (Cmm).
Cmm is a threat to tomato crops globally, causing up to 80–100% crop losses, from wilting, fruit lesions and plant death. Traditional bacterial disease control methods such as antibiotics and copper bactericides have not been successful against this disease in commercial situations, however several fungicides have been shown to suppress Cmm in lab tests.
In New Zealand, Cmm has caused production losses of varying degrees for the past decade in tomato greenhouses. Its impact varies depending on a range of factors, including the crop variety and environmental stresses, and it is known to stay dormant in the greenhouse soil for many years. Once a crop is infected, the only current control measure is creating buffer zones; however, this approach still results in crop losses, ranging from 10% to total destruction. A complicating factor in using buffer zones is plants tend to only show strong identifiable symptoms under summer stress, but are still contagious while asymptomatic.
Bacterial canker (pictured) in tomatoes, caused by Clavibacter michiganensis subsp. michiganensis (Cmm) can cause crop loss. Credit: Dr Andrea Minuto, CERSAA, Albenga (IT).
In evaluating biological control options, the project aims to deliver a sustainable, control option compatible with the greenhouse tomato industry’s integrated pest management (IPM) programme which focuses on the use of biological control agents (BCAs)
If successful, the project would provide a valuable new tool for tomato growers. In addition, assessing Aureo Gold’s efficacy against bacterial diseases other than Psa will generate valuable insights for other ALT stakeholders and may create opportunities to evaluate the product against additional priority diseases.
The project begins with pot trials, followed by efficacy trials in a commercial greenhouse setting if the pot trials show positive results.
The Bioeconomy Science Institute (BSI) has the funded initial work to understand the infection pathways for bacterial canker. This work has identified the inoculation methods to be used to test Aureo Gold efficacy in project trials and contribute to knowledge about Cmm and the future screening of disease management options.
The project is expected to be completed by the end of 2026.
