Maintaining biosecurity standards for soil-borne pathogens and weeds in the strawberry runner industry (BS07014)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Methyl bromide (MB) was a highly effective soil fumigant that was being phased-out due to its ability to degrade the ozone layer. The strawberry runner industry was the last remaining user of MB for soil fumigation in Australia. Phase out of MB in the industry was reliant on trials in this project and registration of methyl iodide (MI), however its withdrawal from Australia meant other alternatives needed to be developed. Australia was only one of three remaining countries applying for ‘Critical Use Exemptions’ (CUEs) under the Montreal Protocol to retain the use of MB. Many other countries were able to adopt fumigant alternatives but these had proven ineffective in the heavy soils and climate experienced in the southern Australian production districts at Toolangi, where strawberry runners were grown. In spite of this, the project had demonstrated many other successful outcomes.

• MB use in the Australian strawberry runner industry had reduced by 6 tonnes since the start of this project owing to identification of alternatives and strawberry varieties (lower chill nurseries) for specific growing regions in northern Australia that could adequately transition to existing alternatives.
• Data showed that soil fumigation with the alternative MI provided the same biosecurity and certification standards in terms of pathogen control, weed control, runner yields and quality, and human safety as MB.
• Data on MI was submitted to the Australian Pesticides and Veterinary Medicines Authority (APVMA), Office of the Chief Plant Protection Officer, and Strawberry Certification authorities to expedite approvals for registration, market access and use in certification schemes. Since completing this work, however, the registrant notified the APVMA in June 2012 that it had withdrawn the application for MI due to the high cost of iodine worldwide at the time.
• Data from this project supported the registration of two new alternatives (PicPlus® and Telone C60®). Although these alternatives proved unsuitable for strawberry runners, they were effective for fruit growing and were now the two most widely used fumigants in the strawberry fruit industry.
• New application techniques, such as drip fumigation, were identified that improve the efficacy of alternatives in the strawberry fruit industry. Data was used to support the registration of this technique for some MB alternatives (e.g. Telone® products).
• New alternative fumigants or methods were shown to be effective in trials and show promise for replacing MB in the runner industry with further development, e.g. recaptured MB from quarantine applications combined with chloropicrin (Pic).
• The project also identified new fungicide spray regimes that combined different chemical classes for managing Gnomoniopsis fructicola in runners and this reduced the likelihood of fungicidal resistance.

Without registration of MI, there were few alternatives for the runner industry to phase-out MB. Industry and government needed to consider: (1) ongoing CUE applications for MB, or (2) accepting the risks of reduced biosecurity levels in runners with MB alternatives used at the time and determining the legal responsibility for this risk.