Recent outbreaks of Phytophthora species (i.e., P. ramorum, P. kernoviae and P. alni) in the United States, United Kingdom and European Union are thought to be caused by the movement ornamental plants and trees through the nursery trade. The rapid spread of these plant pathogens via movement of horticultural products across international or interstate lines, or within state borders, is a direct threat to the biosecurity of these regions. Each of the pathogens listed above have caused enormous, well-documented declines in native forests adjacent to nurseries involved in the sale and distribution of infested plants and plant products. These incursions have had huge economic and political impacts on the nursery industries within these countries. Consequently, governmental regulation in those countries of plant production and movement has increased at federal, state and county level.
In Western Australia (WA), disease due to Phytophthora cinnamomi (Phytophthora dieback) has spread across wild and urban lands through water, soil and direct root-to-root contact. Dieback in the natural environment is managed through many shire and state-level agencies, as well as volunteer groups, yet no organisation is responsible for monitoring disease within the state due to plant trade, other than the Nursery and Garden Industry of Australia (NGIA) itself.
The NGIA are a self-regulated industry. While they must comply with some regulation by Australian government on the issues of hygiene, such as international import/export regulations as required by the Australian Quarantine Inspection Services (AQIS), the NGIA is a self-imposed entity that creates and enacts their own regulatory practices. Despite strict hygiene protocols and response strategies, nursery conditions are very conducive for disease. Release of Phytophthora disease within WA from plants both produced in and out-of-state is highly likely. Additionally, recent studies show that some plants can carry Phytophthora diseases without showing symptoms, confounding efforts to exclude unhealthy plants from trade. This study aims to identify the presence of Phytophthora species in plants sold from production nurseries in WA.
A set of 20 plants, representing major families of ornamental plants, determined to be commonly purchased and susceptible to Phytophthora disease were purchased directly from a major production nursery in WA and brought to the glasshouse facility at Murdoch University. Roots were examined for symptoms of disease, and tested for Phytophthora disease via standard baiting techniques with subsequent plating on selective media. Recovered isolates were identified by sequencing the internal transcribed spacer region of ribosomal DNA. The sampling will be repeated seasonally, and expanded to include other production nurseries in WA. Results will be discussed with regards to implications for nursery policy.