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New beetle to beat pest plant

Wednesday, 11 May 2011 12:30 p.m.

It may be a handsome beetle but what's more attractive is the way it eats - it's the Tradescantia Leaf Beetle, one of the latest biological control agents to be released in the region.

This is the second release of the beetle in the Bay of Plenty with a release carried out at a site south of Tauranga last month.

Bay of Plenty Regional Council Biosecurity Officer Tim Senior said the adult beetles had been released in the Opotiki area in the eastern Bay of Plenty this week to help control the problematic pest plant Tradescantia fluminensis - more commonly known as Wandering Jew.

"This is an aggressive pest plant that forms extensive, sometimes deep carpets which can obliterate all native ground covering" Mr Senior said. "It's also commonly hated by gardeners and it's almost impossible to get rid of."

Mr Senior said it was the leaf beetles' larvae which did most of the damage.

"Although the adult beetle chews holes around the edges of the leaf, the main damage is caused by the larvae which graze the tissue off the leaves, mostly on the undersides, and can eventually skeletonise them," Mr Senior explained.

The beetle is highly host-specific and it is highly unlikely that anything other than this pest plant will be attacked. Other agents that feed on the stems and growing tips are also being considered for introduction to work alongside this beetle.

Mr Senior said the release of these insects was not a quick fix as it would require some time for them to establish and impact on the pest plant population.

The Environmental Risk Management Authority (ERMA) has approved the release of the Tradescantia Leaf Beetle as a biological control agent in New Zealand after rigorous testing.

Sites where the beetle has been released will be monitored and when sufficient numbers have been established the beetle will be redistributed to other parts of the Bay of Plenty.

Bay of Plenty Regional Council assists Landcare Research with funding for biological control programmes. This Tradescantia Leaf Beetle joins a group of eight biological control agents to be released around the region in the past two years.

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Tradescantia leaf beetle release Tim Senior 2011 lowres