The dreaded myrtle rust disease is coming into the surrounds of Melbourne and metropolitan Melbourne and all home gardeners (and lovers of nature) need to be aware of what it looks like and what to do if they see it.
It is a fungal disease only recently found in Victoria and poses a serious threat to Victoria's nursery, forestry and bee keeping industries, not to mention our public parks, native forests and gardens and our home gardens; our places of sanctuary. It has the potential to attack all species of the Myrtaceae plant family. serious concern because the fungus spreads very easily and because the Myrtaceae is a dominant plant group in both natural ecosystems and the plantation industry.
Myrtle rust poses no threat to human or animal health.
Interestingly, this disease has only been detected in Australia for a very short time, and has spread quite quickly in that time. It was first found in NSW in April 2010 and by December of the same year, the "Myrtle Rust National Management Group" realised that it would not be able to eradicate it.
It is up to every one us Australian, Victorians, New South Waliens, etc, to do our little bit in keeping our eyes peeled for it, and then following the correct procedures once we have seen it. We also have to be mindful about moving foliage from one forest to another, what is on our tyres once we leave or enter a National Park: are we putting this park into a vulnerable state.
What does myrtle rust look like?
The two pictures above give a representation of the myrtle rust disease on two plants. It attacks young, soft, actively growing leaves, shoot tips and young stems, as well as fruits and flower parts of susceptible plants.
The first signs of myrtle rust infection are tiny raised spots that are brown to grey, often with red-purple haloes. Up to 14 days after infection, the spots produce masses of distinctive yellow/orange spores.
In Victoria, it is a legal requirement that any suspected myrtle rust detection be reported to DPI.
Phone the Exotic Plant Pest Hotline 1800 084 881 (toll-free), or email photos of the suspect material, together with a contact phone number and the plant’s location, to firstname.lastname@example.org
To avoid spreading the disease, samples of suspect plants should not be touched, moved or collected.
Which plants are affected?
All members of the Myrtaceae plant family are potential
hosts of myrtle rust.
The family includes:
- gum trees (Eucalyptus)
- bottlebrush (Callistemon, Melaleuca)
- tea tree (Leptospermum)
- lilly pilly (Syzygium, Acmena, Waterhousea)
- paperbark (Melaleuca)
- myrtle (Backhousia)
- guava (Psidium)
- midyim (Austromyrtus)
- rose apple (Syzygium)
- brush box (Lophostemon)
- New Zealand Christmas bush (Metrosideros).
Which plants are not affected?
Plants which are not in the Myrtaceae family and therefore
not hosts of myrtle rust include:
- stone fruit
- pome fruit
- crepe myrtle
However, these and other non-Myrtaceae plants may show similar symptoms due to infection by other rusts.
How does it spread?
Rusts are highly transportable because they can produce large numbers of very small spores.
Myrtle rust can be dispersed by:
• movement of infected plant material (e.g. nursery stock, cut flowers, plant cuttings, germplasm)
• movement of contaminated equipment (e.g. secateurs, chainsaws)
• wind, water (wind-driven rain, irrigation) and gravity
• animals (e.g. insects including bees, birds, other wildlife, pets)
• humans (e.g. on clothing, shoes and jewellery)
There are things that you can do if you find it in your home garden, other than just reporting it.
How to treat myrtle rust in your home garden
1. Use an approved fungicide
The Australian Pesticides and Veterinary Medicines Authority (APVMA) has issued permits for the use of certain fungicides to control myrtle rust in home gardens and to decontaminate infected myrtle rust host plant material before disposal. The permits can be accessed via the DPI website at www.dpi.vic.gov.au/myrtlerust. Your local nursery or chemical supplier may also be able to assist.
Before using a fungicide, read the permit together with the product label to determine the applicable directions for use.
In severely infected areas, susceptible host plants should be removed, since re-infection after fungicide treatment is highly likely.
Protection may be improved by treating a plant with fungicide after removing infected parts.
2. Remove infected plants
Infected plants should be removed and disposed of in a way that minimises the spread of myrtle rust.
a. Spray infected and unaffected plants with a fungicide 3-4 days prior to removal. If fungicide treatment is not possible, carefully wet the plants prior to removal to dampen any spores likely to be dispersed during removal.
b. Remove plants. Small plants should be enclosed in a plastic bag before being either pulled or dug out. For potted plants, the whole plant, plus the pot, should be placed into the bag and sealed, if practical. If pots need to be retained, they should be thoroughly scrubbed with detergent and water, then left to dry completely before they are used again.
Larger plants that do not fit in waste bins can be cut into smaller pieces, securely covered with black plastic or similar and put in a sunny place for 3-4 weeks to kill spores.
c. Dispose of bagged plants by burying on-site, placing in general domestic waste bins, or transporting in a covered vehicle/trailer to a general waste disposal site (not a green waste site). Do not use infected plants as mulch.
3. Remove healthy plants
To reduce the risk of a significant infection developing on your property, plant species known to be highly susceptible to myrtle rust can be removed prior to infection.
Healthy plants showing no signs of infection can be discarded as normal garden waste. If you are unsure whether plants are infected with myrtle rust, use the methods outlined above for removing diseased plants.
Please note: The removal of native vegetation may require a planning permit. Residents who are considering this option should seek advice from their local council on whether or not a permit is required.
After removing and disposing of infected plants, wash clothing and clean any equipment with water and detergent before starting other activities that may infect further plants.
You can reuse pots, wooden stakes and other items that have been in contact with an infected plant. However, you should thoroughly scrub these items with detergent and water, and leave them to dry completely, before reusing them.
If infected plants have been removed, replanting with similar species, or other Myrtaceae plants, may result in re-infection. Select replacement plants that are unlikely to become infected. Contact your local nursery for advice. In bushland areas, including regeneration sites, use local plants not known to be affected by myrtle rust.
Where I got this information and Where to get the most up to date information:
Go to the Department of Primary Industries of Victoria website for the most up to date information on Myrtle Rust Disease:
Remember, always, seek advice when dealing with plant diseases and don't take a piece of diseased plant to your nursery for identification. You can take a picture of it to show them instead, or email the photo to the DPI team at email@example.com where they will be able to allay your fears, or assist you with the treatment program.