Farmers in Northland are urged to be vigilant and proactive for Madagascar ragwort (Senecio madagascariensis), an aggressive weed that is spreading rapidly and poses a serious risk to pastoral farming.

This plant is already widespread in the Far North and spreading in the Mid-North. It can devastate pasture productivity, with reports showing carcass weight reductions of up to 35% and 65% losses in milk solids per hectare where infestations have taken hold.

Madagascar ragwort is highly toxic and can be fatal to livestock, even in hay or silage, and there is no treatment available for affected animals.

The weed’s ability to spread is alarming: a single plant can produce 10,000 seeds within six weeks, germinating year-round after warm rain. Seeds are carried by wind and easily transported on fodder, stock, vehicles, machinery, and clothing.

The rapid growth to seed set means it is much more difficult and costly to control than other pasture weeds. There is no single approach that effectively controls all life stages without damaging beneficial pasture species, meaning it requires a carefully timed, ongoing control programme to limit its impact.  

Protect your farm

You can help protect your farm by having good biosecurity practices in place. This includes sourcing hay and other fodder products from unaffected areas, and making sure any equipment, machinery or vehicles coming on to your property are clean. Avoid moving stock from affected areas or utilise a ‘quarantine paddock’ for new stock.

Finding and controlling this plant early is important, so make sure everyone on the farm knows what to look out for. If you see an unknown yellow flowering plant in or near your pasture, confirm its identification. If unsure, place a good-sized sample with flowers in a sealed bag and bring it into your local Northland Regional Council office, or to your rural supplies Technical Advisor. Be very careful not to disturb seedheads or spread seed when controlling or transporting Madagascar ragwort.

Once detected, early and regular control must be undertaken to prevent plants seeding, or the infestation and seed bank can quickly become unmanageable. 

You can find more detailed information on control, identification, and current distribution on our Madagascar ragwort web page and in our Pest Control Hub.  

If you already have significant amounts of Madagascar ragwort on your farm, contact our Pest Plant Biosecurity team on 0800 002 004 for the best advice for your situation.