Parasite's threat to native plants greater than first thought

8:20 pm on 1 September 2017

By Andre Chumko, Reporter

A parasite which puts native plants under threat could be more dangerous than originally thought, new research shows.


Nematodes are worm-like organisms that can survive for up to three years in soil on shoes. Photo:

The findings released today by research group Better Border Biosecurity (B3) showed worm-like organisms, called nematodes, could survive for up to three years in soil attached to travellers' shoes, or on shipping containers imported into the country.

Nematodes were estimated to cause billions of dollars of crop damage worldwide each year.

AgResearch research scientist Mark McNeill told Nine to Noon the organisms were found to be extremely hardy and could endanger our native wildlife.

Research samples were collected and analysed over three years from declared footwear at the New Zealand border, he said.

"For every gram of soil, we could find something like 41 nematodes, about 2.5 seeds, we even found insects and mites which was pretty impressive.

"It was just an extraordinary result," he said.

This sparked further research into how long the nematodes could survive, Mr McNeill said.

After 12 months, nematodes appeared to die, but when the organisms were put next to plants, including white clover and rye grass, they could survive and lay eggs.

The findings provided evidence to justify cleaning footwear and shipping containers, he said.

Nematodes were easily transferred because travellers put their shoes into suitcases, which were ideal environments for sheltering the parasites.

"Potentially anything that's caught in those boots or your running gear could be carried onto your golf green, or into another park or onto farmlands."

New Zealanders were mostly aware of the biosecurity risk of not cleaning their shoes, but it was important to continue to encourage travellers to do so anyway, he said.

The study found the risk of transfer of nematodes was higher when walking through forest areas.

The average weight of nematodes on footwear was about three grams, and the average weight on shipping containers was about 400g.

Despite the volume being higher, the study found the risk of transfer was lower because shipping containers were usually placed on concrete slabs.

Mr McNeill said if nematodes were picked up early, they could be destroyed by incinerating them, but if they became established, they would be difficult to kill off.

The study found mountain bikes and vehicles could also carry nematodes.

B3 is a multi-partnered science group which researches ways to reduce the entry and establishment of new plant pests and diseases in New Zealand.

Its partners include AgResearch, Plant and Food Research, Landcare Research, Scion, Forest Owners Association, Bio-Protection, Environmental Protection Authority, Department of Conservation and MPI.

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