Department of Conservation (DoC) is urging Hawke's Bay residents to be on the lookout for the destructive myrtle rust.

DoC Hawke's Bay community senior ranger Chris Wootton says myrtle rust is a fungal disease which has the potential to decimate myrtle species found in New Zealand.

"The myrtle family of trees includes native species such a rata, pohutukawa, manuka, kanuka, ramarama and swamp maire. Introduced species of myrtle include feijoa, guava and eucalyptus."

The region is currently free of the disease, but late summer and autumn are predicted to be the worst time for infection and spore spread, he says.

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"Myrtle rust generally attacks soft new growth including leaf surfaces, shoots, buds, flowers and fruit.

"Symptoms to look out for are: bright yellow/orange powdery patches on leaves, brown/grey rust pustules (older spores) on older lesions leaves that are buckled or twisted and dying off."

DoC's Hawke's Bay senior biodiversity ranger Denise Fastier says the pest has the potential to impact not only our native biodiversity and taonga species, but also our economy.

"If you suspect myrtle rust infecting plants in your garden or in areas you visit through the Hawke's Bay — don't touch it. Record the location, take a picture if you can and call the MPI hotline."

First detected in May 2017, at a Kerikeri nursery, myrtle rust was then confirmed at several sites in the Taranaki region. Less than a year later, myrtle rust appeared in the Tasman region of the South Island, says Chris.

In case of plants severly infected by myrtle rust leaves may become twisted and die. Photo / Supplied
In case of plants severly infected by myrtle rust leaves may become twisted and die. Photo / Supplied

"It's likely that tiny spores of myrtle rust were carried into New Zealand by strong winds from Australia. Myrtle rust has spread rapidly around the world over the last 40 years, establishing as a pest in many countries.

"Myrtle rust damages the new growth of host plants, with repeated infections over time weakening, even killing, the host plant. The effect of myrtle rust has been compared to how people with immune deficiency become more susceptible to other diseases and illness. Other stresses, such as browsing possums or insects, or climate extremes like drought, can then devastate already weakened plants."

Biodiversity and ecosystem values are threatened by the establishment of myrtle rust, as well.

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"With the rust attacking new shoots, flowers and fruit, this can disrupt the food chain relied on by native birds, lizards, insects and bats. The longer-term impact of myrtle rust on key forest tree species such as pohutakawa and rata may result in a wider collapse of forest ecosystems."

DoC is working in partnership with Biosecurity New Zealand and others to safeguard the mauri or lifeforce of myrtle species and their dependent ecosystems.