Taranaki nursery and garden centre, Big Jim's, has been shut to the public due to myrtle rust disease.

A Taranaki nurseryman said it was inevitable an outbreak of myrtle rust disease would spread further once the first signs were detected in Northland earlier this month.

Big Jim's Nursery and Garden Centre owners Vince and Ann Naus discovered myrtle rust spores on 20 six-month-old pohutukawa plants during routine checks of the nursery on Thursday morning.

The couple immediately notified Ministry for Primary Industries, and within two hours staff took away samples to Auckland to be analysed.

ANDY JACKSON/Fairfax NZ Myrtle rust has been discovered at Big Jim's Garden Centre in Taranaki

Within 24 hours the results of the samples were not what the Naus' wanted to hear and confirmed the "yellow pustule-type" spores found on the plant leaves was myrtle rust, Vince Naus said.

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The business was one of three properties in North Taranaki to date where myrtle rust disease had been discovered.

ANDY JACKSON / FAIRFAX NZ Myrtle rust has been discovered on Big Jim garden centre owners Ann and Vince Naus' business.

Two properties in Northland had also been confirmed by MPI.

"It was just a matter of time for the spores to spread after they were discovered in Northland," Naus said.

"It was inevitable when it got to Raoul Island we would be next, we're the closest to Australia."

The couple's 18 year garden centre and nursery business was now a 'restricted area' under 24 hour MPI surveillance and all trading had been stopped until further notice.

All plant deliveries and organic material in and out of the premises beside State Highway 3 had also been stopped.

"Not even lawn clippings, if I mow the lawn, can be taken away," Naus said.

A cafe on site would still be open to the public.

Naus said the couple wanted to be open to their customers about the discovery of the disease even though it could shut down the business for an unknown time period.

"We could have gathered up the infected plants and chucked them away without telling anyone," he said.

"It is more important to let MPI know that the disease is here than try and cover it up.

"We wanted to get it out there so there was no doubt which nursery had been infected, and other nurseries were not involved."

Naus said the unknown effect of the disease on plants was the hardest to grapple with.

"We just don't know what it can do, it's a matter of just waiting and see how it develops."

Naus said the discovery of the disease on his nursery plants was "heartbreaking.''

"We check all the plants every day as a matter of course."

He was certain the spores had been wind blown, and were not in the root stock when the young plants had been brought into the nursery to 'grow on' six months ago.

"The plants were in the nursery close together in a warm, wet environment which is an ideal site for the transfer of spores."

The couple are more concerned the disease, which has been in eastern Australia since 2010, could potentially destroy native trees from the myrtleceae family, such as pohutukawa, kanuka, manuka, rata and ramarama.

"No one knows exactly what will happen, it's the unknown and what affect it will have on the native trees which is the real concern for us," Ann Naus said.

"There are 1000's of plants in the myrtleceae family which are susceptible to the disease."

Fungicide can be sprayed on the plants to contain the disease but it is not known how effective it would be, the couple said.

"You would need to get rid of the whole thing but the hope is it can be contained as much as possible.

"We don't know if it will actually kill the plant, or just make it look manky at certain times of the year."

The only thing the couple know is that they did the right thing in alerting the ministry as soon as possible.

"The ministry staff have been incredibly supportive," Vince Naus said.

"We want to get the word out that people who discover the disease on their land need to know they will be supported," he said.

The couple are not insured but have been assured by MPI they will be compensated for any financial loss.

"We want to turn a negative into a positive."

Fifty MPI staff were in Taranaki undertaking ground surveys with all nurseries and plant centres to identify the extent of the disease spread in the region, MPI regional controller Mark Bateman said.

MPI encouraged the public to report any suspected signs of myrtle rust to MPI's exotic pest and disease hotline 0800 80 99 66.

Staff warn not to touch the rust, or the plant but note the location and take photos of the symptoms and the plant.