Rust diseases are quite common in Australian agriculture, with the grains industry being constantly on alert for the seasonal disease risks and trying to stay one step ahead by planting the latest resistant varieties. But one recent exotic rust disease is causing concern in industries that have not previously had to worry about them.
Myrtle rust was first detected in Australia in April 2010 on a property growing Australian native plants for the cut flower industry on the central coast of New South Wales.
Later in 2010, despite efforts to suppress the disease, Myrtle rust was found in several nature reserves and some state forests in the Central Coast of NSW and subsequently in Queensland.
Myrtle rust has now spread along the east coast of Australia, from coastal areas of Queensland and NSW to Victoria. Although technically it is no longer considered an exotic pest, any new outbreaks of Myrtle rust should be reported as part of the ongoing monitoring process.
Mr Rod Turner, General Manager of Programs at Plant Health Australia, said: “The last two years have seen high rainfall in summer months allowing the rust to spread at a rapid rate.”
The Myrtaceae family of plants that are affected by Myrtle rust includes many Australian native species, such as tea trees, bottle brushes, hakeas and eucalypts.
Mr Turner said: “It’s not known yet exactly how many species are susceptible to Myrtle rust, but the Myrtaceae family includes a wide variety of plants commonly grown for the cut flower industry, in nurseries, home gardens, urban landscaping and native forests.”
Species of Myrtaceae are found in all parts of Australia, so the potential impacts are quite large, particularly in native forests where control measures are extremely limited.
“Rust spores can be easily spread on contaminated clothing, infected plant material, equipment and hand tools, by insects, and by wind” said Mr Turner.
Myrtle rust typically attacks young plants and new growth on established plants, as well as fruits and sepals on some species. Leaves may become buckled or twisted as a result of infection. On turpentine and callistemon, rust lesions are purple in colour, with masses of bright yellow or orange-yellow spores.
Tea trees grown in Australia for essential oils are now at risk of infection from this disease. Tea tree growers are finding that sound farm biosecurity practices can help to minimise the impact of the disease and limit its spread within their property and local region.
In time, growers will be able to select less susceptible plants, but until then they are encouraged to phase out susceptible and very susceptible varieties because of the risks to the whole industry. But if these cultivars are grown, then Mr Turner advises that a management plan, ready in advance, is prepared in case of a Myrtle rust outbreak.
“Having a plan for when a pest is detected on your property is one of the best defences against pests and diseases becoming established” said Mr Turner.
“Your individual management plan must take into account your property’s level of risk, including summer and seasonal rainfall, location and variety selection” he said.
A range of tactics has been used to manage the Myrtle rust outbreaks in commercial operations in Australia, including the use of fungicides and other disease management measures.
Here are six simple, routine practices you can do to reduce the threat of new pests entering and establishing on your property. Each practice should be embedded in everyday management practices.
1. Be aware of biosecurity threats
Make sure you and your workers are familiar with the most important pest threats. Conduct a biosecurity induction session to explain required hygiene practices for people, equipment and vehicles on your property.
2. Use only clean, pest-free and preferably certified, production inputs
Ensure pests and other contaminants do not enter your property with production inputs, such as growing media, fertiliser and propagation material. Purchase these only from reputable suppliers, preferably with industry accreditation or certification. Keep records of all inputs.
3. Keep it clean
Practicing good sanitation and hygiene will help prevent the entry and movement of pests onto your property. Workers, visitors, vehicles, raw material and equipment can spread pests, so make sure they are decontaminated, or have come from a clean source, before entering and leaving your property. Have a designated visitor’s area and provide vehicle and personnel disinfecting facilities.
4. Check your plants
Monitor your plants and raw materials frequently. Knowing the usual appearance of the plants in your property will help you recognise new or unusual events and pests. Keep written and photographic records of all unusual observations. Constant vigilance is vital for early detection of any exotic plant pest threat.
5. Abide by the law
Respect and be aware of laws and regulations established to protect your industry, Australian agriculture and your region.
6. Report anything unusual
If you suspect a new pest – report it immediately.
More general biosecurity tips are available from the Biosecurity Manual for the Nursery Production Industry, developed by Plant Health Australia and the Nursery and Garden Industry of Australia.
The Nursery and Garden Industry of Australia has developed the Australian Nursery Industry Myrtle Rust Management Plan to assist in the management of Myrtle rust on all plants from the Myrtaceae family in nurseries, garden centres, hardware stores and supermarkets.
At present, Myrtle rust is a notifiable disease across Australia. Any detection of the disease should be reported to the relevant state or territory biosecurity agency within 24 to 48 hours or by calling the Exotic Plant Pest Hotline on 1800 084 881. People are asked not to take samples to prevent inadvertently spread the disease. It is better to mark the spot to make it easy to return to later, take a photo and send it to your local Department of Primary Industries.