Once covered in ragwort, a Manawatu farm is now almost free of the stock-threatening weed thanks to the introduction of moths and beetles.
Kiwitea dairy farmer Wayne Bennett credits the cinnabar moth, flea beetle and plume moth for ridding the farm of the yellow-flowered weed that had spread through the farm two years after he bought it.
Ragwort has the ability to compete with pasture species and contains alkaloids that are toxic to stock. A single plant can produce more than 50,000 seeds.
Bennett said the insects had taken a few years to become established but had become successful.
"We're extremely happy with how well bio-control has worked on our farm as we don't like to use a lot of spraying to control weeds."
Horizons Regional Council said annual property inspections in Manawatu had indicated bio-control agents were having positive effects.
Environmental management officer Neil Gallagher said all three insects used to control ragwort were present at a recent visit to two Manawatu dairy farms and the landowners considered control to be at a good level.
There was an abundance of cinnabar moth caterpillars in particular.
"It was obvious the combined effects of the bio-agents working together were keeping the ragwort at acceptable levels."
He said pest plant staff would continue to monitor sites to assess how the insects were performing and move them to places where they were needed.
- Manawatu Standard