Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Farmer Grateful for Tiny Beetle

Hangatikei today, no longer a ragwort farm.

Hangatikei today, no longer a ragwort farm.

"Ragwort’s (Jacobaea vulgaris) distinctive bright yellow flowers used to be a familiar sight across New Zealand farmland. But thanks to a tiny flea beetle the weed, which is particularly toxic to cattle and horses, is now largely under control, saving farmers millions in control costs. Recently one North Island farmer has explained what this biocontrol project has meant for his farm.

Waikato dairy and beef farmer Steve Fagan was sceptical to say the least when tiny beetles were released on his farm about 25 years ago to control ragwort. “When Jim Laurenson, the local biosecurity officer, released flea beetles onto my property I said he was a fool to do so. I thought it was a big joke.” But he would later eat his words. “Ten years on, I went back to shake his hand and say thanks,” Steve said.

The ragwort flea beetle (Longitarsus jacobaeae), first introduced to New Zealand by Landcare Research in 1983, worked. In fact, a recent quantitative study by Landcare Research has found it is saving dairy farmers across the country $44 million in control costs alone every year. The Fagans, who say the weed nearly ‘broke them’, aren’t surprised.

The weed has now almost disappeared from the Fagan’s 1000-acre Hangatiki property, but the beetles are still there.  His wife Maxine said the farm, which they purchased 42 years ago, used to be overrun with ragwort. Looking at the lush green pastures, now full of clover, it’s hard to imagine. “We had what we would call a ragwort farm,” she said.  “We had to use a rotary crusher to cut tracks for the cows. That’s how bad it used to be,” Steve said. The family lost several cows to the weed.  “No one wanted to buy the farm when we bought it because it had so much ragwort,” Maxine said.

The couple used to spray the weed with chemicals daily to try and get it in check. But this not only killed the weed but also the grass. “We’d milk early, milk late, and spray all day. We’d spray 2500 litres most days to try and get it under control. We thought we’d never get rid of it. It cost thousands. We even tried running sheep but they only made it grow thicker.  It nearly broke us,” Steve said.

“These days it’s more about milking the cows. We still have the odd ragwort plant, but we used to have paddocks of it.”  Maxine said news of the biocontrol’s success spread fast in the community. “Cars lined up our road all coming to get the beetle.”

Not all biocontrol agents work as quickly as the flea beetle.  Some areas where the flea beetle had been released were almost clear of ragwort in as little as two years, and within about 10 years, in most drier climates around New Zealand where we had released the beetle, ragwort had pretty much disappeared. But the flea beetle didn’t prove a solution for every region, struggling in wet conditions.

“In areas where rainfall exceeded 1700 mm/year the flea beetles simply couldn’t cope adequately with the conditions,” said Hugh Gourlay. As a result, the weed continued to persist, particularly on the West Coast, as well as Southland, parts of Otago and the central North Island. The West Coast community rallied and with Hugh’s help established the West Coast Ragwort Control Trust (WCRCT). The group was granted funding by the Ministry for Primary Industries Sustainable Farming Fund to search for another biocontrol agent. In 2005, a plume moth that was proving successful in controlling the weed in wet conditions in Australia was released after extensive testing.

“Three to five years later, we had the same result we had with the flea beetle, ragwort populations started disappearing,” Hugh said. “Between the two agents almost throughout New Zealand ragwort has become relatively rare.” Areas where ragwort continues to persist are those where the plume moth has yet to be established or where spraying, often by landowners who are not aware of the biocontrol agents, is preventing these insects from working. Sometimes all that is needed is for spraying to stop to allow these highly effective biocontrol agents to take over.

A video about this project is available at:

The study to estimate the value of ragwort biocontrol in New Zealand was funded by the Ministry of Business, Innovation and Employment as part of Landcare Research’s Beating Weeds Programme.