Tuesday, 09 March 2010
RICHARD Sisam reckons he spends $50,000 a year trying to get rid of thistle from the pasture on his Taneatua farm.
Now he’s hoping a tiny beetle will save him an awful lot of money.
The green thistle beetle has a ravenous appetite for thistle, and it is the latest biological weapon in Environment Bay of Plenty’s pest control armoury.
Beetle larvae have been introduced on to Sisam and Sons dairy and sheep farm which, at 4500 hectares, is one of New Zealand’s biggest.
The logic is simple - the beetles will grow and multiply and devour the strangulating thistle that defies tens of thousands of dollars of annual spraying.
“Californian thistle is an aggressive pest plant that’s well established in the Bay of Plenty,” EnvBOP pest plant officer Des Pooley said.
“Control of the thistle costs our farmers millions of dollars each year in control and lost production through sprays, tractor time and loss of pasture alone.”
It is the beetle’s larvae which does most of the damage to the thistle.
“The larvae feed on the leaves and defoliate plants. Because the female beetle can lay as many as 1000 eggs in her lifetime, we expect there will often be all life stages of the insect present,” Mr Pooley said.
He said the release of the beetles was not a quick fix as its introduction would require ongoing and wider on-farm thistle control.
But for Mr Sisam, it is welcome reinforcements in the battle.
“Californian thistle has a big root system and it is very expensive using spray to kill it, so anything like this is a help,” he said.
“The thistle spreads everywhere and displaces pasture so stock don’t want to graze there.”
Sisam and Sons infrastructure manager Bill Wycherley said he was optimistic about the green thistle beetle.
“I’ve seen first-hand the benefit these types of insects can have, through the introduction of the ragwort flea beetle, so I’m especially interested to monitor the effects of this beetle,” he said.
The Environmental Risk Manage-ment Authority has approved the release of the 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 re-distributed to other parts of the Bay of Plenty.
EnvBOP assists Landcare Research with funding for biological control programmes and the hungry beetle joins a group of six bio-control agents released in the Bay of Plenty in the past year.