First confirmed myrtle rust case on West Coast

Biosecurity New Zealand, a branch of the Ministry for Primary Industries, was notified of the potential find on a commercial property in Greymouth. 

Investigations have confirmed it is myrtle rust and now Biosecurity New Zealand is advising local gardeners, orchardists and nurseries to monitor their trees and take protective action if they see signs of the disease.

This is the first case found on the West Coast but is not a surprise, as it was identified as an area where myrtle rust would likely become established. The fungus has been spreading rapidly across New Zealand since the first case was identified in 2017.

"Its spores are spread on the wind, by insects and birds, and on plant matter and machinery, and we have no real way to stop it," says John Sanson, manager of recovery and pest management for Biosecurity New Zealand.

"It is now well established across most of the North Island and the top of the South. Our recent focus has been on developing resources for communities, landowners and nurseries so that people can identify the disease and know what to do if they find it."

Myrtle rust is a fungal disease from South America that affects trees in the myrtle family, including natives such as pōhutukawa, rātā, mānuka and ramarama as well as exotics like bottlebrush and lilly pilly. It attacks new growth, preventing trees thriving.

"If you think you have myrtle rust on your plants, we have material on our website (www.myrtlerust.org.nz ) that will help you identify it,” says Sanson. 

"The main way to manage it is by removing infected material, using good hygiene to prevent cross-contamination of plants, and avoiding pruning in warm spring and autumn months when plants are actively putting on new growth. There are no fungicides proven effective against myrtle rust available to home gardeners."

The Department of Conservation (DOC) wants the public to watch out for myrtle rust in the West Coast region.

"We currently don’t know how badly myrtle rust will impact our native ecosystems. It may affect flowering of our native plants, which are an important food source for our native birds and insects," says Fiona Thomson, DOC’s myrtle rust project manager.

"To help us monitor the impacts on our precious myrtles in our national parks and reserves, we are asking for everyone to keep an eye out for myrtle rust and report it on inaturalist.nz.

Monitoring may identify natural resistance to the disease in some plants which would then allow us to mitigate the impacts in the longer term.