Fireweed is a heavily branched daisy-like plant. Photographer: H Rose. Image: © State of New South Wales.
Fireweed (Senecio madagascariensis) continues to be one of the most troublesome pasture weeds across New South Wales (NSW).Its bright yellow flowers may look harmless, but Fireweed is a highly invasive species that competes aggressively with pastures and poses significant toxicity risks to cattle, sheep, goats, and especially horses.
Effective management requires vigilance, particularly between March and June, when Fireweed is most visible and actively growing across southern NSW.
Why Fireweed is a priority this season
Fireweed thrives in overgrazed or neglected pastures, quickly forming dense infestations that suppress valuable feed species. The plant contains pyrrolizidine alkaloids, which cause irreversible liver damage in livestock. Horses are especially vulnerable, often showing neurological signs such as dullness, incoordination, and photosensitivity. Cattle and sheep can also suffer weight loss, poor growth, and in severe cases, sudden death. 1
With March to June marking the peak Fireweed window in southern NSW, early detection and treatment now can prevent large-scale spread later in the year. 2
Identifying Fireweed
Fireweed is an annual or short-lived perennial herb that varies in size depending on environmental conditions. It typically grows 10 to 60 cm tall and produces small, bright yellow daisy-like flowers with 13 to 15 petals. Seedlings flush after rain, especially in warm conditions, and all growth stages may be present simultaneously. The plant’s fibrous root system and prolific wind-dispersed seeds make it capable of rapid expansion across paddocks, fencelines, and disturbed soil areas.
Priority actions between March and June
1. Inspect paddocks regularly
Autumn is a high-risk period. Walk high-traffic areas, gateways, and lightly grazed paddocks to spot early seedlings. Immediate removal helps prevent seed set and establishment. Hand pulling is effective when soil is moist, ensuring the entire root system is removed.2
2. Target young plants with herbicides
Chemical control is most effective when Fireweed is young and actively growing, typically the case during autumn and early winter. Trials in NSW show the highest success at the seedling stage using bromoxynil formulations such as Bromicide® 200.
Always follow label instructions and consult local authorities regarding legal requirements under NSW pesticide regulations.
Ace Ohlsson Agronomist recommendations
Chemical control
- Bromicide 200 (bromoxynil) is only suitable on the early seedling stage of fireweed (up to 4 leaf stage) and requires an 8 week withholding period for grazing and cutting. It is a S7 rated product and will require a spray license for usage.
- Grazon Extra is also registered for spot spraying, No with holding period applies
- Method - Aminocyclopyrachlor 240 g/L - Registered for spot spraying, any life stage of the weed, no with holding period (although the fireweed may become more palatable and stock should be kept off until it’s died off).
Supplemental actions
Graziers may opt to over-sow with a beef or equine seed blend such as Equine Blend or Hawkesbury Blend to aid in better coverage and inhibit further growth.
Many graziers use grazing management (such as rotational grazing) to improve pastures and reduce weeds, including fireweed. Fireweed often proliferates when pasture is overgrazed.
The presence of fireweed is an indication of poor pasture management and the ultimate goal should be pasture improvement.
3. Strengthen pasture competition
Healthy, dense pasture is your best long-term defence. Avoid overgrazing late in summer, as bare soil encourages Fireweed germination. Sowing winter-active species and maintaining good ground cover helps suppress Fireweed seedlings during the cooler months.2
4. Manage risk for horses and sensitive stock
Equine centres should be especially vigilant. Horses are more prone to Fireweed poisoning and may develop severe neurological symptoms. Remove stock immediately from infested areas, and ensure hay and silage are free of Fireweed contamination.1
A seasonal opportunity
March to June is an ideal intervention window: plants are young, visible, and responsive to control. Combining regular monitoring, strategic herbicide application, and strong pasture management will significantly reduce Fireweed spread and protect your livestock— as well as your bottom line.
If Fireweed is emerging on your property, now is the time to act.
References:
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