Fireweed (Senecio madagascariensis)

Fireweed looks like a daisy with little yellow flowers. It invades pastures and can poison livestock.

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How does this weed affect you?

Fireweed invades pastures and disturbed areas. It:

• reduces productivity
• is poisonous to livestock and can cause death
• is difficult to control.

Livestock poisoning

Fireweed contains chemicals called pyrrolizidine alkaloids. Livestock that eat it get liver damage. The damage is irreversible and gets worse the more fireweed an animal eats. Hay, silage or grain contaminated with fireweed plants or seeds can poison livestock.  Identifying fireweed poisoning is difficult. If you think you have affected animals contact your vet.

Cattle

Cattle are usually reluctant to eat fireweed. Young, hungry or new stock not familiar with fireweed are more likely to eat it. Cattle can lose weight, or their growth slows. Some develop brain damage, which can show as confusion and poor coordination. Sudden death can happen in fat cattle that have eaten fireweed in the last 3 to 6 months.

Sheep and goats

Sheep and goats are more inclined to eat fireweed than cattle. They are also up to 20 times more tolerant of its toxins. Merinos tend to eat less fireweed, other sheep breeds can eat it to excess. Sheep that eat fireweed over two or more years may become unwell or die suddenly. Sheep and goats rarely show signs of brain damage.

Fireweed can poison alpacas too, but less is known about the effects on them.

Horses

Horses have more problems with fireweed poisoning. Unpigmented skin can become sensitive to sunlight, redden and peel away. Brain damage is common. Symptoms can include: dullness, aimless wandering, an uncoordinated gait, pressing up against fences, gates or trees and possible blindness.

What does it look like?

Fireweed is an annual or biennial herb 10–60 cm tall. It is erect with many branches. Flowering is mostly from spring to autumn but times vary for different parts of NSW. All stages of the plant from seedlings to flowering may be present at any time of year in some locations. Flushes of seedlings appear after rain in warm weather.

Leaves are:

• bright green
• fleshy and narrow
• 2–7 cm long and 3–10 mm wide
• smooth, toothed or lobed on the edges
• stalkless and clasped around the stem 
• alternate along the stems.

Flowers are:

• small, yellow and daisy-like with up to 15 petals
• 1–2 cm in diameter
• in clusters at the ends of branches
• emerging from a small cup of modified leaves called bracts (usually 21 bracts)
• more abundant on some plants than others and up to 200 per plant.

Seeds are:

• small and light
• 1–3 mm long
• cylindrical in shape
• downy on the surface
• attached to fine, white feathery hairs that aid in dispersal by wind.

Roots are:

• fibrous
• 10–20 cm deep
• branched from a central taproot.

Similar looking plants

Variable groundsel (Senecio pinnatifolius) is sometimes confused with fireweed. It’s a native Australian plant, not considered a weed. Often it grows in places where fireweed is unlikely to be, such as bushland and undisturbed sites.

Where is it found?

Fireweed grows along the Australian east coast from Victoria to Central Queensland. It is most invasive in coastal regions. It is also on the northern and southern tablelands. 

Fireweed comes from southeast Africa. It was first seen in the Hunter Valley in 1918.

What type of environment does it grow in?

Fireweed thrives in:

• overgrazed pastures
• disturbed or cultivated soil
• most soil types.

Fireweed does not grow well in shaded areas or wet areas. It does not survive waterlogging.

Maps and records

• Recorded presence of Fireweed during property inspections (Map: Biosecurity Information System - Weeds, 2017-2024)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

Each plant can produce up to 18 000 seeds. Wind spreads the light, hairy seeds. Most seeds fall within 5 m of the parent plant but some can be blown much further. Spreading beyond one kilometre is more likely through human activity. Fireweed is spread:

• in contaminated hay, silage and grain products
• by livestock birds and other animals
• by sticking to clothing, vehicles or machinery

Do not bale pastures with fireweed for silage or hay.

More information

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Control

Long-term fireweed control needs to consider that:

• most new seedlings appear in autumn
• many new seedlings appear after rain when temperatures are 15–27°C
• seedlings grow fast and can flower 6–10 weeks after emerging
• flowering and seeding occur mostly in spring
• most plants die off by late spring
• some plants live for up to three years - the tops die back in spring and regrow the following autumn
• fireweed seed buried deeper than two centimetres is unlikely to germinate
• long-term follow up is essential because about 15% of seeds remain dormant for over 10 years.

In pastures, combine grazing strategies, pasture improvement and strategic herbicide use.

In environmental areas hand-pull individual plants and spot spray herbicide.

Avoid introducing it

Avoid bringing hay, feed or silage from known fireweed areas onto your property.  Keep checking feedout areas and paddocks for fireweed plants. Control them before they flower and seed.

Look out for it

Spot fireweed plants in new areas and act quickly to control them.

Maintain healthy pastures

Maintain healthy pastures as the best long-term defence against fireweed. Have good autumn–winter pasture cover to suppress new fireweed plants. Avoid grazing too hard. Weeds like fireweed then establish in thin and bare patches. To maintain healthy pasture cover:

• grow combinations of winter and summer pastures
• rest pastures between grazing periods
• test soil to check fertility
• use fertiliser if needed.

Improve poor pastures

Large patches of bare ground and lots of weeds are signs of poor pastures. Pasture improvement to control fireweed is proven to work best north of Sydney where there’s more rain in summer). South of Sydney it rains more in winter and pastures are slower to establish. Selective herbicides may be needed to control fireweed until pastures mature. Pasture improvement aims to:

• sow vigorous pasture plants that compete with fireweed
• cover bare soil
• correct soil fertility problems

and adjust grazing to:

• always keep at least 90% of the ground covered with good pasture plants
• have even higher cover during peak fireweed germination in autumn
• reduce numbers of grazing animals before overgrazing.

Be careful with fertilisers. Applying them before competitive pasture species are present can increase the fireweed problem.

Suitable summer-growing pasture species include:

• setaria
• kikuyu
• paspalum
• Rhodes grass.

Winter or spring-growing pasture species include:

• phalaris
• cocksfoot
• fescue
• ryegrass
• white clover
• subterranean clover.

Consult your agronomist for appropriate pasture species, fertiliser recommendations and pasture establishment techniques. More fireweed can germinate after disturbing the soil.

Tillage

An agronomist can advise on a crop program to support fireweed control in arable areas. This can reduce the fireweed seed bank before sowing a perennial pasture. Tillage in March and April stimulates many fireweed seeds to germinate. Control the seedlings with a  knockdown herbicide or more tillage. Avoid over-cultivation, which increases the risk of erosion. Then sow a forage crop that will give dense cover to suppress remaining fireweed.

Native pastures

Seek advice from your Local Land Services office when improving native pastures. Some activities are restricted.

Grazing to control fireweed

Grazing fireweed harms all animals. Even though sheep and goats can tolerate it the effects build up over time. Don’t force stock to eat only fireweed. Make sure other feed is available. Avoid grazing fireweed in late spring as it can promote its survival into the following year.

Sheep and goats

The best animals to control fireweed by grazing are:

• goats or sheep wethers intended for slaughter
• other sheep if you can use a new group of animals each year.

Merinos seem to be more resilient than other sheep breeds. Avoid pushing breeding stock of any species including sheep and goats to graze fireweed.

Cattle and horses

Cattle and horses normally avoid eating fireweed and heavily graze other pasture plants. This favours the growth of fireweed. Always match grazing pressure of cattle and horses to the available pasture growth or the fireweed will increase.

Hand weeding

Pull out individual plants in small, isolated patches or sensitive environmental areas. Wear gloves to protect skin from the plant’s poisons. Bag and dispose of the pulled out plants. They are still poisonous to livestock and produce viable seeds if they have flowers.

Slashing and mulching

Careful slashing or mulching can reduce fireweed seeding when done:

• before late spring
• when less than 25% of plants are flowering
• at least every six weeks if pastures can recover faster than the cut fireweed plants

Wait two weeks before grazing slashed areas. Livestock are more likely to eat the cut, wilted fireweed.

Avoid slashing or mulching in late spring, or when more than 25% of plants are flowering. This can trigger plants to regrow, surviving into summer rather than dying off at the end of spring. That makes next season’s control harder.

Biological control

There are no effective biological control agents available for fireweed. It’s difficult to find a biological control that’s harmless to the native Senecio species.
These insects can attack and sometimes destroy fireweed plants:

• A chrysomelid beetle (Chalcolampra species)
• A magpie moth (Nyctemera amica)
• A blue stem borer moth (Patagoniodes farinaria).

They cannot be relied on for control. The damage usually occurs after the plants have produced seeds

Chemical control

Herbicides are most effective in combination with healthy, competitive pastures. The best time to treat fireweed with herbicide is late autumn. This controls the peak numbers of seedlings and young plants. By late winter herbicide treatments are much less effective.

Used correctly, selective herbicides don’t kill grasses but do slow their growth. They can kill legumes, which are important pasture plants. Blanket applications of selective herbicide are problematic because pasture growth is set back. Wherever possible limit the application areas in paddocks.

Bromoxynil herbicides cause the least damage to legumes but only kill young fireweed plants. Protect legumes by applying only when the maximum daily air temperature will be below 20°C. Metsulfuron-methyl herbicides can kill older fireweed plants, but also kill pasture legumes.

Flowering plants can be spot sprayed with herbicides containing aminopyralid or metsulfuron-methyl.

Herbicide options

See Using herbicides for more information.

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PERMIT 87436 Expires 30/04/2024
Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 g in 100 L of water
Comments: Spot spray with powered handgun or knapsack in at least 1000 L water per hectare. For best results, apply in Autumn. Apply only ONE application per year. See permit for further critical comments.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High

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PERMIT 87436 Expires 30/04/2024
Metsulfuron-methyl 600 g/kg (Various products)
Rate: 40 g/ha (in a volume of 100L water per hectare)
Comments: Boom spray: For best results, apply in Autumn. Apply only ONE application per year. See permit for further critical comments.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High

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Bromoxynil 200 g/L (Bromicide®)
Rate: 1.4 L/ha
Comments: Boom spray seedlings. Apply during the Autumn-Winter period when weeds are young and actively growing. Not effective on mature plants.
Withholding period: Do not graze or cut for stock food for 8 weeks after application.
Herbicide group: 6 (previously group C), Inhibition of photosynthesis at photosystem II - D1 Histadine 215 binders (PS II Histadine 215 inhibitors)
Resistance risk: Moderate

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Bromoxynil 200 g/L (Bromicide®)
Rate: 2.8 L/ha
Comments: Boom spray plants in the early flowering stage. Apply during the Autumn-Winter period when weeds are young and actively growing. Not effective on mature plants.
Withholding period: Do not graze or cut for stock food for 8 weeks after application.
Herbicide group: 6 (previously group C), Inhibition of photosynthesis at photosystem II - D1 Histadine 215 binders (PS II Histadine 215 inhibitors)
Resistance risk: Moderate

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Bromoxynil 250 g/L + Diflufenican 25 g/L (Jaguar)
Rate: 500 mL per ha
Comments: Booms spray application, up to 4 leaf stage
Withholding period: Do not graze or cut for stock food for 8 weeks after application.
Herbicide group: 12 (previously group F), Inhibition of carotenoid biosynthesis at the phytoene desaturase step (PDS inhibitors) + 6 (previously group C), Inhibition of photosynthesis at photosystem II - D1 Histadine 215 binders (PS II Histadine 215 inhibitors)
Resistance risk: Moderate/Moderate

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Fluroxypyr 140 g/L + Aminopyralid 10 g/L (Various products)
Rate: 500 mL in 100 L of water
Comments: Spray flowering plants up to 30 cm tall.
Withholding period: Not required for pastures when used as directed. Do not graze or cut crops for stock food for 7 days after application. See label for export restrictions.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Fluroxypyr 140 g/L + Aminopyralid 10 g/L (Various products)
Rate: 1.5 L/ha
Comments: Spray seedling plants up to flowering
Withholding period: Not required for pastures when used as directed. Do not graze or cut crops for stock food for 7 days after application. See label for export restrictions.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 350 mL in 100 L of water
Comments: Spray flowering plants, cover the foliage thoroughly.
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW	Prohibition on certain dealings Must not be imported into the state, sold, bartered, exchanged or offered for sale.
Central Tablelands An exclusion zone is established for all lands in the Central Tablelands region except the identified core infestation area. A core infestation area is established for the Bylong Valley - Ulan and Kanimbla Valley (lower Cox River catchment) areas.	Regional Recommended Measure* (for Regional Priority - Containment) Within exclusion zone: Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Within core infestation area: Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Central West	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
North West	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Riverina	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Your local biosecurity weeds officer can help to identify, advise on control, and how to remove this weed.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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Disclaimers

Pasture improvement may be associated with an increase in the incidence of certain livestock health disorders. Livestock and production losses from some disorders are possible. Management may need to be modified to minimise risk. Consult your veterinarian or adviser when planning pasture improvement. The Biodiversity Conservation Act 2016 and Local Land Services Amendment Act 2016 restrict some pasture improvement practices where existing pasture contains native species. Contact Local Land Services for further details.

Reviewed 2024