A parasitic wasp has saved the agricultural sector nearly half a billion dollars in the decade since it was released and the farmer at the centre supports more such biological controls.
The Irish parasitic wasp Microctonus aethiopoides was first released into a paddock on Kerry Robbins' dairy farm in the Rai Valley, between Nelson and Blenheim, in 2006.
It was aimed at the destructive clover root weevil, which had been discovered established in the North Island 10 years earlier.
The wasp lays its eggs in the adult weevil and when they hatch the grub makes the weevil infertile. The grub kills the weevil as it eats its way out.
Now AgResearch, the body responsible for introducing the wasp, says the $8.2-million programme has saved the agricultural industry at least $489m, based on reduced production losses on sheep and beef farms, and reduced use of urea fertiliser to compensate for weevil damage.
It estimates the ongoing benefits are worth $158m a year.
"It's a fantastic example of how our science is making a real and profound difference to our agricultural sector and economy," said science team leader Alison Popay.
"The wasp was so successful the team found that it reduced weevil populations by around 90 per cent in monitored areas where the wasp is well established."
However, it said it wouldn't completely remove the weevil.
Mr Robbins said the weevil still seemed to be prolific in the area but there was no longer the "shot gun" effect of damage to clover.
Since then, other pests had turned up - varroa had been a disaster for wild bees - and he supported the further use of biological controls.
"I was just open to suggestion - anything biological that can control something a minimal cost to the landowner."