Last week (start of May 2017) the alien fungus myrtle rust was found on five young pohutukawa in a Kerikeri nursery that specialises in propagating native plants. The nursery owner promptly reported the find which was confirmed soon after. An intensive biosecurity response then began. On the following Tuesday a second sighting was confirmed on a private property near the source of the original outbreak. Another possible sighting in a second plant nursery requires further testing.
At present there is intensive surveillance within a 500m radius around the first nursery as well as in or around a variety of other strategic locations. The plants in the affected nursery have been sprayed with a strong fungicide. Because of the risks posed to New Zealand’s native plants and ecosystems, as well as the Manuka honey industry, feijoas, guavas and eucalypts, the Government is treating this incursion very seriously.
So what could myrtle rust do?
It is a fungal disease that infects plants in the Myrtaceae family, often with serious consequences. Native plants at risk include: pohutukawa, northern and southern rata, various species of climbing rata, manuka, kanuka, ramarama, rohutu and swamp maire. Introduced plants at risk include eucalypts, feijoas and guavas. In Australia 10% of their native flora and 75% of their vegetation is dominated by plants from the Myrtaceae family. Over 300 hosts of myrtle rust have been found in Australia. In New Zealand there are 104 species in the myrtle family. Many of these are non-native species.
Young plants and new growth are most susceptible. There is damage to leaves, stems and fruit. In some species it can lead to death. Myrtle rust could cause significant damage to native ecosystems as has been observed in Australia.
What is myrtle rust
Myrtle rust is caused by the fungus Autropuccinia psidii. It is native to South America. Myrtle rust has also been found in Central America, the Carribean, Mexico, USA, Japan, China, South Africa and New Caledonia. It was first detected in New South Wales (Australia) in 2010. In Australia today myrtle rust is found in Tasmania and along the eastern seaboard from Victoria to Queensland. Myrtle rust can be spread by wind, water, vehicles, machinery, insects, clothing including hats, and animals.
Myrtle rust spores require darkness, moisture and 15-25⁰ C temperatures to germinate. Spores can remain viable for three months. Northland and much of the rest of the North Island would be perfect for myrtle rust. If you think you have seen myrtle rust, don’t touch it and phone the MPI hotline 0800 80 99 66.
For more information see: http://www.mpi.govt.nz/protection-and-response/responding/alerts/myrtle-rust
Myrtle rust
Vicky Froude, 9 May 2017