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Keep eyes peeled but hands off myrtle rust

1 Dec 2017

Keep eyes peeled but hands off myrtle rust

Environmental and science manager Lois Easton is urging people to keep a look out for myrtle rust on the region’s pōhutukawa, eucalyptus and mānuka trees.

While it hasn’t been officially found in Gisborne, Lois says it is possible it's already here and just gone unnoticed.

The rust is a serious fungal disease that affects plants in the myrtle family, which includes pōhutukawa, eucalyptus and mānuka. It has devastated ecosystems in Hawaii and the east coast of Australia and been identified in the top three biosecurity threats to New Zealand by the Ministry for Primary Industries.

“It's a tremendous threat to pōhutukawa particularly,” says Lois. “The pōhutukawa seems very susceptible. Any chance we have of controlling its spread lies in early detection and we need our community out there being our eyes on the ground, looking out for it.”

She’s quick to add – look but don’t touch.

“Just take a photo and call us. It can spread easily from disturbance.”

A new app has been designed to help people take part in a nationwide move to monitor myrtle rust. The new bilingual app allows them to record a dozen potential host plants and  easily report anything they find suspicious. The myrtle rust reporter app is freely available in the iPhone and Android app stores.

Check these plants regularly and look for telltale yellow spores on new growth.”

Lois says the whole district falls into the high risk category, and particularly up the East Coast where rainfall can be high and temperatures hot.

In March myrtle rust was found to be widespread on pōhutukawa on Raoul Island, and in early May was found in plants at a nursery in Northland. In the following two months it was found in Taranaki, Waikato and in July, in the Bay of Plenty. It has now been found in Auckland.

Myrtle rust generally attacks soft, new growth, including leaf surfaces, shoots, buds, flowers, and fruit. The spores are microscopic and can easily spread across large distances by wind, or via insects, birds, people, or machinery.

The spores are thought to be capable of crossing the Tasman Sea from Australia to New Zealand on wind currents, and the experts say that is probably how it arrived on our shores.

The disease thrives in moist conditions with temperatures of 15-25 degrees when it is easily able to be identified on infested plants. MPI is working to identify approaches to managing this disease, however rust diseases are notoriously difficult to control. Early detection of any outbreak in New Zealand will be vital to any attempt to manage it.

Severe infestations can kill affected plants and have long-term impacts on the regeneration of young plants and seedlings. It is not known how this disease will affect New Zealand species.

How to spot myrtle rust

Symptoms to look out for on myrtle plants are:

Bright yellow powdery eruptions appearing on the underside of the leaf (young infection)

Bright yellow powdery eruptions on both sides of the leaf (mature infection)

Brown/grey rust pustules (older spores) on older lesions.

Some leaves may become buckled or twisted and die off.

The first signs of myrtle rust infection are tiny raised spots that are brown to grey, often with red-purple haloes. Up to 14 days after infection, the spots produce masses of distinctive yellow spores.

Myrtle RustMyrtle Rust 01.pngMyrtle Rust 01

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