Marlborough weed checker finds wandering vines in unexpected places

A wild Ben Minehan olive tree found in the Boulder Bank, Marlborough. Supplied / Ben Minehan

A Marlborough weed checker has found an increasing amount of wild vines and wild olive trees in the area.

Ben Minehan, owner of Weed Solutions and former biosecurity officer for Marlborough District Council, said with the two plants being grown “on such a large scale” they could become a big weed problem.

“I’m now starting to see wild grapes and wild olives starting to spread into the environment, which are in our reserve-type areas,” Minehan said.

“Which is concerning because it has happened before with kiwis, they are spreading into adjacent areas.”

He said he had spotted crops of grapes at Starborough Creek in Seddon, in the Wairau River bed, in Blind River and on Whangamoa Hill.

“Probably the one that worries me the most is that they were growing in Grovetown Lagoon on Māori Island,” he said.

Each weed had a “lag phase”; how long it took them to establish themselves, Minehan said.

“I would say we have to recognize that as a problem. They have to be controlled.”

Anyone who spots a wild plant should kill it before it can produce fruit, he said.

“Birds pick up fruit and move it around.

“I found some olives when we were a gorse spraying team for the Department of Conservation, and I found three olives growing on the White Bluffs (on the east coast of Marlborough). no olives growing there, it must be birds.

“Because these are bird-propagated plants, they will eventually spread very quickly, to new areas.

“It would be nice to start recognizing it early. The easiest thing to do is kill a vine early before it spreads.”

Marlborough District Council’s biosecurity officer Jono Underwood said most plants could be propagated either by seed or discarded vegetative material – however, not all self-propagated plants exhibited invasive characteristics and have become a biosafety issue.

“It’s more about how quickly and successfully they spread, become established, and then dominate an ecosystem or productive system,” Underwood said.

He said the wild kiwi has shown it can do it, hence the “recent attention”.

He said it was likely there were still other species to “show up”.

This was highlighted in the Parliamentary Environment Commissioner’s report ‘Space Invaders’, published in November last year.

“It’s something that the council’s biosecurity team, with the help of the community, always keeps an eye out for…the new or the unusual,” he said.

Underwood did not believe that wild grapes, or olives, had “caring, invasive” characteristics, and therefore were not of concern to the council.

Marlborough Plant and Food’s lead scientist, Dion Mundy, didn’t think wild grapes in New Zealand would be likely to ‘persist’.

“But you can grow vines from seed, grapes will. It will take them a while to grow until they produce fruit,” Mundy said.

“They will, of course, be genetic recombinations of the parents that could be totally different varieties. They could be red, they could be white, they could be anything in between.”

With the large number of grapes at Marlborough already, he didn’t think ‘one or two more wild plants’ would make too much of a difference to disease pressure.

However, in the United States there were wild vines that were a reservoir of pests and diseases, but New Zealand didn’t have those particular pests here, he said.

“So I wouldn’t be concerned about the grapes growing and not being sprayed,” he said.

“The only disease it could be a problem with is some of the virus diseases. If he was infected with a virus and there was a lone vine outside of someone’s property, and it got was going to an adjacent property,” he said.

“But then someone’s Sauvignon Blanc who doesn’t have symptoms could also spread to a nearby Pinot Noir.”

Local Democracy Reporting is public interest journalism funded by NZ On Air

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