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Members of a multi-agency biosecurity response team check for signs of myrtle rust soon after its discovery in Kerikeri.

More myrtle rust discoveries in Northland have prompted a plea from biosecurity officials for residents to continue to report any suspected cases of the serious fungal plant disease.

The latest discoveries in Kerikeri and Mangawhai come one month after the Ministry for Primary Industries (MPI) and Department of Conservation (DOC) announced that – given the prevalence of the rust across susceptible parts of New Zealand – the fight against it was changing gear.

MPI spokesperson Dr Catherine Duthie admitted containing the rust hadn't proved possible.

"We have signalled for a while the likely need to change gear from intensive surveillance and the removal and destruction of host plants to one where we look to manage the disease over the long term." 

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Since the disease was first found at Kerikeri Plant Production nursery in May, 2017, it has been found at over 400 sites in six regions. 

The threat is not only to native trees like pohutukawa, manuka and rata; it can also attack common plants like feijoa and eucalypts.

Symptoms include bright yellow powdery eruptions on the leaf or brown or grey rust pustules (old spores) on older lesions. Leaves could buckle, twist and die off.

Over the past year more than 95,000 plants have been inspected and several thousand destroyed.

Northland Regional Council Biosecurity Manager Kane McElrea says recent tests had confirmed the presence of myrtle rust at new sites in Kerikeri and Mangawhai.

With more than 50 infected trees over 20 sites covering six square kilometres in Kerikeri alone, news the rust had now reached other parts of Northland was disappointing but not unexpected, he said.

McElrea encourages Northlanders to check their properties for signs of the rust but stresses if they do discover symptoms, it's extremely important not to touch the plant.

"Myrtle rust spores are microscopic and can be easily spread across large distances by wind, or via insects, birds, people, or machinery so instead of touching a suspicious plant, call the MPI hotline immediately."  

Dr Duthie said going forward, a key focus will be working with communities to support regional efforts to combat myrtle rust.

This could include regional surveillance programmes, identification and protection strategies for taonga plants and special locations, advice to landowners and seed banking.

Dr Duthie said MPI and the DOC would be engaging with iwi and hapu, local authorities, the plant and nursery industries and communities to support the development of regional programmes.

• Report sitings at MPI Hotline 0800 809 966.

 - Stuff