A tiny new air force has been launched in the war against foreign invaders on Wairarapa soil.
The green thistle beetle was released yesterday at a Rangitumau farm, as a way of helping farmers control the Californian thistle, which crowds out pasture.
Staff from Greater Wellington Regional Council joined interested farmers as
a container of about 60 of the insects was opened in a flat paddock overlooking the Tararuas, belong to Rangitumau farmer Peter Wyeth.
Landcare Research scientist Hugh Gourlay had brought the beetles in a small cookie container containing leaves, beetles and eggs from where they had been raised at a site in Lincoln University.
Mr Gourlay said each female beetle was "a really amazing egg factory", producing 100 to 300 eggs in its one-year lifetime, even though the eggs are at least a quarter the beetle's size.
By next year, Mr Gourlay is hopeful there will be an established population of up to 1000 in the paddock, and after five or six years could have travelled with the wind up to 20km away.
Mr Gourlay said he had great hopes that the bettles would "be established, will build rapidly, and build into large numbers".
Mr Gourlay noted, however, that the thistles have an "enormous root mass underground" and it remains to be seen what effect the beetles would have on the whole population.
Greater Wellington senior biosecurity officer Richard Grimmett said the adult beetles feed sparingly on the thistle, but the larvae can defoliate the plant, if there are enough of them.
Green thistle beetle is proven in parts of America to reduce the density of Californian thistle infestations by up to 80 per cent.
"It would be great if it was that successful here; however it takes many years to get that kind of success," Mr Grimmett said.
"Bio-control is a long-term strategy to controlling pest plants.
"It can be very effective and has the bonus of being labour and cost-free once it is established at a site."
Green thistle beetles were released at sites in Southland and Otago in 2007 and have survived the past winter, which bodes well for them establishing and having an effect.
