Sunday, August 14, 2022

Xylella joins least wanted line up

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The country’s “least wanted” list of biosecurity pests and diseases has had the bacteria xylella added to it, as industry officials witness its devastating effects on crops in California and Italy.

Xylella has wiped out millions of olive trees in Italy, and is starting to affect Spanish plantings.

The country’s “least wanted” list of biosecurity pests and diseases has had the bacteria xylella added to it, as industry officials witness its devastating effects on crops in California and Italy.

The risk the disease poses to a variety of crops, including grapes, olives, berries, summerfruit and even lucerne, was highlighted by Better Border Biosecurity (B3) director David Teulon at Zespri’s recent biosecurity seminar.

He says xylella was rated as “high” on a number of industry radars as a significant threat, with efforts being made to better understand the vectors in New Zealand that could transmit it and what strains may be picked up here by plants and crops.

Italy has endured major olive crop devastation from the disease that is passed from plant to plant via insect vectors, and often does not manifest until one to three years after being infected.

Since 2013, millions of trees have been killed and it is now threatening plantations in Spain and Greece, which combined are the source of 95% of Europe’s olive oil.

In California, vineyards have been wiped out by the bacteria known as Pierce’s disease, now an epidemic in southern California and transmitted by the sharpshooter insect.

NZ Winegrowers biosecurity manager Sophie Badland says so far there has proven to be no effective cure for the disease.

“Sentinel plants” from NZ planted in California have shown to be vulnerable to the bacteria’s infection and there was to be a follow up on this work,” Badland said.

“As world trade has increased, it has come to the forefront as a risk. In Australia it is the top pathogen they want to keep out.”

Following along the lines of preparing for a brown marmorated stink bug outbreak, industry here is working on a preparedness plan for response action, should an outbreak occur.

Plant and Food Research scientists are one year into a five-year project aimed to fill current knowledge gaps about xylella in a NZ disease context, including improving understanding of both endemic and native vectors that could transmit the disease.

Badland says while NZ did not have the sharpshooter insect that was the Californian vector, NZ did have spittlebugs that were native and an introduced species that transmitted the disease through Italian olive groves.

She says the disease was complicated by having at least 500 plants that are vulnerable to the disease, multiple vectors and assorted strains of bacteria that can be transmitted.

A 2019 report to the wine industry by Plant and Food Research estimated horticultural production valued between $300 million and $1.7 billion a year would be at risk if it became established in NZ.

The impact would, however, depend upon the strain that afflicted NZ and how far it spread.

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