Sizer said he first noticed some yellow-flowering weeds while moving cattle four years ago.

He didn’t pay attention to it until he returned to the same enclosure three weeks later and discovered a sea of ​​yellow flowers.

He sent a sample for identification and was told it was Madagascar ragwort (Senecio madagascariensis), a fast-spreading plant poisonous to livestock.

Sizer said he removed the plant by hand, a laborious method, but the only one that worked.

His neighbor hired someone two days a week just to weed the Madagascar groundsel by hand.

“It disperses very easily with the wind. A plant seed head will contain thousands of seeds and it will take over. It colonizes areas.

“It’s not good for the livestock if they have to eat it because there’s no grass; it can cause serious health problems.

When Sizer noticed the plants spreading across State Highway 10 in the spring — some fields around Waipapa were entirely yellow from the flowers — he decided it was time to act.

He contacted the Northland MP Grant McCallumalso a farmer, and launched a petition calling on the government to take urgent action.

Sizer said the first thing to do is an awareness campaign.

“A lot of people see it in their pasture, on their lawn and they don’t know what it is and how deadly it is or that if they leave it, the seeds will spread everywhere.

“So we need a national campaign to make sure farmers, growers, landowners and the community are aware of the seriousness of this weed. »

There was also a need for accelerated research into biological and herbicide control, as was financial assistance to Northland farmers who were bearing the costs associated with weed control.

“The problem is if one farmer is in control and the other isn’t, as soon as the wind blows you’re back to square one.

“So it needs to be a Northland-wide approach and, potentially, a national-wide approach, so that we can deal with the problem quickly, efficiently and effectively,” he said. he declared.

The seeds could also be spread with hay, so Sizer wanted Northland to designate a “controlled area” for animal feeding to help prevent seed dispersal. This would prohibit the movement of hay or bales out of the area.

Without a proper national action plan, Sizer said weeds would take over the landscape and dominate pastures.

“I have nightmares about it. That’s how serious it is. But I’m determined to get rid of them.

Northland Regional Council biosecurity manager Joanna Barr said Madagascar ragwort was spreading aggressively in the region.

Some farms in the Far North, where the weed was first identified, were already experiencing high density infestations similar to groundsel (Jacobaea vulgaris) before the introduction of biocontrol agents in the 1980s.

Barr said Madagascar ragwort contained toxins that caused permanent liver damage when grazed, leading to disease, low milk production and slow growth and sometimes death of livestock.

Cattle and horses were particularly susceptible, she said.

It was toxic when green or dry, so contaminated hay or silage could also be harmful.

There was also no effective treatment for Madagascar groundsel poisoning.

This weed was initially thought to be an almost identical species known as gravel groundsel (Senecio skirrhodon).

However, a genetic analysis carried out at the end of 2022 highlighted the distinction.

Barr said Madagascar groundsel was significantly more invasive than gravel groundsel and posed a major threat to the agricultural sector.

It was already a serious problem in Hawaii and Australia, where it was known as fireweed and listed by the Australian government as a weed of national importance.

It was difficult to control, with dense infestations requiring costly and repeated interventions.

The best way to protect pastures was early identification and intervention, Barr said.

The Ministry of Primary Industries was informed once the plant was confirmed as a new species for New Zealand.

The ministry concluded that the weed was not yet widespread throughout the country, but had been present for 20 years and therefore eradication was not feasible.

Barr explained that livestock were generally reluctant to eat Madagascar ragwort, so poisoning was more likely when the plants were dense and livestock could not feed selectively, or when there was a shortage of pastures and that stocks were less selective when it came to food.

Sheep and goats were more likely to eat Madagascar ragwort than cattle and were also less susceptible to poisoning.

This weed had a broad environmental tolerance and competed strongly with grazing species.

An average Madagascar groundsel plant could produce more than 10,000 seeds per year and growth from seed to flower could take as little as six weeks.

Last year the council commissioned a study to find out if some form of biocontrol was feasible.

However, potential biocontrol agents tested in Australia proved unsuitable.

The next phase of biocontrol research would be to carry out genetic analysis of Madagascar ragwort in its native range, to determine the origin of the New Zealand and Australian infestations.

This area could then be surveyed for new insects and pathogens for further testing, but this would require substantial additional funding.

Barr said improving pastures and reducing grazing pressure reduced germination rates, and mixed grazing with sheep could also help manage Madagascar ragwort, but it was not always practical .

Biosecurity Minister Andrew Hoggard has been contacted for comment.