The tradescantia tip beetle release at Kauri Point, north of Katikati, is the first of its kind for the Bay of Plenty.
The green thistle beetle has already been introduced to specific Bay of Plenty sites and was last week brought to two new sites, both in the Western Bay.
The beetles are among several biological agents being tested and, in some cases, established, across the region. This includes the successful establishment of the ragwort flea beetle, which has helped control ragwort in the region for 20 years.
The tradescantia tip beetle is being released in the hope it will help control the pest plant wandering jew, while the green thistle beetle may help control California thistle.
Successful biocontrol agents can help control pest plants by feeding on them, which can often make the plant stop spreading, or producing viable seeds, and even kill it completely.
The Bay of Plenty Regional Council's manager of western land management, Robyn Skelton, says successful biological control agents can offer a cost-effective, environmentally sustainable way to help control pest plants.
"We've had success with different agents in the past and we are hoping these beetles will establish themselves and help us in our efforts to control these pest plants in the future," Robyn says. "The beetles ... offer good climate matches for their preferred environment. They will be monitored before the council considers introducing them to other areas.
"We've had positive feedback from landowners on the use of these biological control agents," says the council's land management officer, Andrew Blayney. "Some of the plants they tackle are aggressive and extensive and can significantly affect our environment, economy and our people.
"If these beetles establish themselves as we are hoping, then we will look at introducing them to other properties further down the track."
Te Puke farmer Carol Burt attended a council sustainable farming workshop on climate change last year. She was concerned about the effect of climate change on pastoral weeds and was after more information.
After the workshop Carol and council staff worked on strategies to help protect her land against the predicted impacts of climate change. A key element was the trial release of the green thistle beetle, which took place last week on her family farm.
Carol says she is optimistic about the agent establishing.
"We've had releases of other types of agents on our property before and had good success with them. In particular, we had some beetles that were successful in slowing down the spread, and reducing the density of, nodding thistle and Scotch thistle.
"I'm hoping this beetle will also establish itself and contribute to the eradication of Californian thistle on our property, which continues to present a problem for landowners."
The Environmental Risk Management Authority (ERMA) has approved the release of tradescantia tip beetles and green thistle beetles as biological control agents after rigorous testing.
Land Care Research studies found the beetles to be highly host-specific and, therefore, unlikely to attack other plants.