Destructive myrtle rust reaches New Zealand

The fungal plant disease myrtle rust was last month found on mainland New Zealand for the first time.

Also known as guava rust and eucalyptus rust, the disease poses a significant threat to a wide range of iconic indigenous plant species such as pōhutukawa, kānuka, mānuka and rātā that are part of the Myrtaceae plant family, as well as introduced myrtaceae plants eucalyptus, guava and feijoa.

Myrtle rust can spread rapidly and while it has currently only been located in Northland and Taranaki, as gardeners we need to be vigilant for any signs of the disease. Here’s what you need to know:

Why is it such a threat?

It can result in plant death. It infects the leaves of the plants making them susceptible to secondary infections and can cause dieback and distortion that affects the plants function.

A loss in plant function can have serious consequences, for example if this happened to the manuka and kanuka plants the New Zealand honey industry would be impacted.

What does it look like?

Powdery, bright yellow or orange-yellow rust-like spots on leaves, tips and stems.

How did it get into New Zealand?

It’s believed it was carried in the wind as myrtle rust spores are a windborne pathogen capable of being carried long distances.

What damage is it going to do?

The full extent of damage it could cause is somewhat unknown as internationally its effects have varied from plant to plant. Since an outbreak in Australia in 2010 it has devastated several of their indigenous plant species and this could happen here in New Zealand also.

How is it spread?

It’s carried by the wind and on people, vehicles and equipment and because the spores are microscopic preventing its spread is a challenge.

What to do if you spot it?

Report it immediately to the Ministry for Primary Industries (MPI) on 0800 80 99 66. Do not touch it or the plant as this could cause further spread. Note its location and take photos if possible