Botanic gardens are special places for people to relax, learn and enjoy plants. They also play an important role in plant conservation, research and to raise public awareness about the importance of biodiversity. The living collections held by Australian botanic gardens are an immense biological resource of information on both individual plants and plant biodiversity.
An emerging threat to plants in the Myrtaceae family, both within botanic gardens and the Australian landscape, is a recently introduced fungal disease Myrtle rust.
Myrtle rust is a fungal disease affecting plants in the Myrtaceae family, including Australian natives like bottle brushes, tea trees and eucalypts.
Rust diseases are very specific to plant species and Myrtle rust is unlikely to affect plants other than those in the Myrtaceae family. Myrtle rust on affected plants is typified by a large number of yellow spores that can be easily spread by wind, humans and animals.
The spores prefer high humidity, low light, temperatures over 15 °C and moisture on leaves and stems to germinate.
Myrtle rust belongs to a group of fungi known as the ‘guava rust complex’. This complex of diseases is native to South America and also present in Hawaii, Florida and Mexico. It is not known how the disease entered Australia.
Myrtle rust first emerged on the central coast of New South Wales in April 2010. It has since been detected along the NSW south and north coast and into South East Queensland and as far north as Cairns.
Due to the increasing number of locations that Myrtle rust has been detected and expanding host range, further spread of the disease is anticipated.
The first signs of rust infection are tiny raised spots on young, actively growing leaves, shoot tips, young stems, fruits and flower parts. The spots develop into powdery bright yellow or orange-yellow pustules after a few days. The pustules turn pale yellow then grey with age.
If untreated, the disease can cause deformed leaves, heavy defoliation of branches, die-back and stunted growth.
Many popular Myrtaceae garden plants are affected by Myrtle rust and gardeners should be vigilant in monitoring their home gardens for Myrtle rust.
Australian Network for Plant Conservation: http://www.anbg.gov.au/anpc/resources/Myrtle_Rust.html
Australian Quarantine and Inspection Service: http://www.daff.gov.au/aqis/quarantine/pests-diseases/myrtle-rust/myrtle-rust-qa
NSW Department of Industry and Investment: http://www.dpi.nsw.gov.au/biosecurity/plant/myrtle-rust
Queensland Primary Industries and Fisheries: http://www.dpi.qld.gov.au/4790_19788.htm
Department of Primary Industries, Victoria: http://new.dpi.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/shrubs-and-trees/myrtle-rust
Department of Primary Industries, Parks, Water and Environment, Tasmania: http://www.dpiw.tas.gov.au/inter.nsf/WebPages/MCAS-8DV22F?open
Biosecurity South Australia: http://www.pir.sa.gov.au/biosecuritysa/planthealth/emergency_plant_pests/myrtle_rust
Department of Agriculture and Food, Western Australia: http://www.agric.wa.gov.au/PC_94039.html
Department of Resources, Northern Territory: