Myrtle rust appears as yellow spores. Photo / File
Ninety-three properties in the Western Bay of Plenty have been affected by the fungal disease myrtle rust, which attacks plants such as pohutukawa, manuka and rata.
The Ministry for Primary Industries said myrtle rust was first found in the Bay of Plenty in Te Puke last June.
Since then, a total of 93 properties in the region have been affected – 42 at Te Puke, 22 at Bethlehem, 11 in Tauranga, six at Welcome Bay, three each at Aongatete and Omokoroa, and one each at Bellevue, Maungatapu, Mount Maunganui, Otumoetai, Plummers Point, and Whakamarama.
One is on public land, one is a commercial site, and the rest are residential.
Myrtle rust is a serious fungal disease that affects plants in the myrtle family including pohutukawa, manuka and rata as well as some common garden plants such as ramarama and lilly pilly, the ministry said on its website.
Tauranga City Council manager of parks and recreation Mark Smith said the council was told last week a handful of young ramarama trees on Beaumaris Boulevard had been infected.
Smith said the council would remove the trees in coming days, following advice from the ministry.
A number of other trees in the myrtle family may also need to be removed, including pohutukawa and manuka, which were in contact with the infected trees.
"They'll then be shipped to MPI who will take it from there," he said.
Dr Catherine Duthie, the ministry's myrtle rust response spokeswoman, said the most frequently affected myrtle plant, both in Bay of Plenty and across all regions, is ramarama, which was widely used for garden hedging.
Smaller proportions of other myrtle species have also been affected in Bay of Plenty including pohutukawa, lilly pilly, and bottle brush.
"There has been a steady number of detections in this area and, although the frequency of new detections is a concern, it was expected," Duthie said.
"The Bay of Plenty has climatic conditions that are ideal for myrtle rust, and the region's recent weather – hot, wet, and windy – has been optimal for the growth and spread of the microscopic spores."
In an effort to contain and slow the spread, Duthie said the ministry has had one of its seven field surveillance teams deployed in the Bay of Plenty for several months and the Department of Conservation has also checked plants on public conservation land.
A field surveillance team was investigating notifications to the biosecurity hotline, liaising with affected property owners on the treatment and management of infected plants, and checking and monitoring myrtle plants on properties within 200m of all confirmed infections.
Residents not at home for visits from the team were left a letter and information about myrtle rust in their letterbox.
Duthie said that, as at March 21, there had been a total of 413 properties affected by myrtle rust on mainland New Zealand: Northland (four properties), Auckland (64), Waikato (33), Bay of Plenty (93), Taranaki (202), Manawatu (1) and Wellington (16).
Look out for signs of myrtle rust. If you think you see the symptoms of myrtle rust:
Don't touch it
Call the MPI Exotic Pest and Disease Hotline immediately on 0800 80 99 66.
If you have a camera or phone camera, take clear photos, including the whole plant, the whole affected leaf, and a close-up of the spores or affected area of the plant.
Remember, don't touch it or try to collect samples as this may increase the spread of the disease.
Find out how to identify myrtle rust
Do not attempt to self-treat trees and plants with fungicide, either for a cure or to try to prevent myrtle rust infection. We are still building a picture of whereabouts the disease is present nationally and, if people use preventative sprays, it could suppress symptoms, and prevent us from making the best management decisions for the country.
Risk to New Zealand
Myrtle rust could affect iconic New Zealand plants including pohutukawa, manuka, rata, kanuka, swamp maire and ramarama, as well as commercially grown species such as eucalyptus.
Severe infestations can kill affected plants and have long-term impacts on the regeneration of young plants and seedlings.
It is not yet known how this disease will affect New Zealand species. Overseas its impacts have varied widely from country to country and plant species to species.
- Ministry for Primary Industries