Myrtle rust is native to South America and was first recorded there in the late 1800s. However, it has rapidly spread around the world in the last 40 years, and is now established as a pest in many countries.
Myrtle rust has rapidly spread around the world in the last 40 years, and is now established as a pest in many countries, including South Africa, China, Indonesia, Hawaii, New Caledonia and along Australia's eastern and northern seaboard.
It is likely the fungus arrived in New Zealand carried by strong winds from Australia, according to the National Institute of Water and Atmospheric Research (NIWA).
Myrtle rust was first recorded in Australia in 2010, and was expected to arrive in New Zealand eventually via wind, insect, bird or human movements. As a result, the New Zealand Government banned imported flowers and foliage from Australian Myrtaceae family plants. Biosecurity officials began to develop a range of measures in case the disease spread to New Zealand.
Unfortunately it was detected in New Zealand in March 2017 on Kermadec pōhutukawa trees on subtropical Raoul Island, part of the Kermadec Island chain. In May 2017, it was found for first time on the New Zealand mainland, in Northland, in a Kerikeri nursery. The Ministry for Primary Industries (MPI) immediately put a restricted place notice in effect. MPI staff checked properties surrounding the nursery, set up field headquarters with the Department of Conservation (DOC) and consulted iwi, industry and the local council. By mid-May 2017, several sites in the Taranaki region had confirmation of myrtle rust in commercial and private properties.
Biosecurity NZ staff checking for myrtle rust.
MPI and DOC, with the help of local iwi, the nursery industry, and local authorities ran a yearlong operation to attempt to contain and control myrtle rust and determine the extent of its spread.
With the wind-borne nature of the disease and the abundance of suitable plants that can be infected with myrtle rust in the New Zealand environment, the disease has spread rapidly and is now considered established and widespread across New Zealand.
Less than a year after the disease was first found on mainland New Zealand, myrtle rust appeared in the South Island’s Tasman region. This indicated that the disease had reached most of the country’s high-risk regions.
MPI is no longer involved in field work to manage the disease. MPI offers advice and guidance to landowners with myrtle rust on their properties but allows the landowners to manage the plants themselves. MPI is continuing to collect, analyse and report myrtle rust data.
For a full timeline of events since the beginning of myrtle rust in New Zealand go to the Science Learning Hub's myrtle rust page.
Myrtle rust, also called guava rust or ʻōhiʻa rust in Hawaii, is a plant pathogen that has spread from its origin in Latin America to Hawaii, the Pacific, Australia, and New Zealand in the past few years.
Different strains of the fungus are virulent on different tree species. In severe cases the host tree suffers repeat defoliations and is eventually killed. Efforts to contain or eradicate the rust have so far been unsuccessful.