Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Weevils to wage war on weed

Tuesday 26 Jan 2016

Hugh Gourlay of Landcare Research collects Darwin's barberry seed weevils for release.

Hugh Gourlay of Landcare Research collects Darwin's barberry seed weevils for release.

Hundreds of Chilean weevils will be released over the coming weeks to control the widespread weed Darwin’s barberry.

Around 100 Darwin’s barberry seed weevils were released for the first time in New Zealand in March last year. Landcare Research imported the weevils and conducted extensive tests to make sure they were safe before they were released in Southland. The fast-spreading orange-flowered thorny shrub is a growing problem in parts of the country, threatening to overrun native plants and farmland, particularly in Southland.

Environment Southland is due to release an additional 400 weevils shortly. Horizons Regional Council and the Greater Wellington Regional Council are also deploying the weevil to help combat the weed. Around 1000 weevils would be released across the three regions.

Hugh Gourlay, a member of the weed biocontrol group at Landcare Research, has been rearing the weevils at the Crown research institute’s containment facility in Lincoln for the releases.

He said there was a limited window of opportunity in which the releases could be made.

“We need to release the new adults soon after they start emerging as potted plants do not produce sufficient new growth to nourish them sufficiently.”

Although the adult weevils feed on the new growth, the main damage to the plant is caused by the larvae that feed on the seeds.

Darwin’s barberry produces large numbers of viable seed that can be spread hundreds of metres by birds that consume the fruit on the weed.

Gourlay said weevils were often confused with beetles but their “elongated nose, like an elephant’s trunk” actually set them apart.

The Environmental Protection Authority approved the release of the weevils in 2012. Research into the weevils has been funded by the National Biocontrol Collective.

Subscribe to Weed Biocontrol Alerts

via email