Burr ragweed (Ambrosia confertiflora)

Burr ragweed is an erect perennial herb. Its burrs contaminate wool and pollen can cause 'hayfever'.

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How does this weed affect you?

Burr ragweed is not palatable to stock and by forming dense stands which exclude all other plants can reduce carrying capacity. The burrs cause vegetable fault in wool and are not easily removed because of the hooked hairs. It produces large amounts of allergenic pollen which can cause hay fever.

Where is it found?

Burr ragweed was introduced from the southern USA and Mexico. Burr ragweed infests areas of south-east Queensland and the western slopes and plains of NSW.

Maps and records

• Recorded presence of Burr ragweed 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.
  
  

What does it look like?

Burr ragweed is a perennial herb growing to 2 m high. Leaves are large up to 16 cm long and 10-15 cm wide, they are deeply divided.

Plants die back to the roots over winter but grow rapidly in spring and summer and flower in mid-summer. If dry spells occur in summer plants may die back and resprout in autumn.

Burrs form in clusters with short, stout, hooked spines.

References

Auld BA and Medd RW (1999). Weeds. An illustrated botanical guide to the weeds of Australia. Inkata Press, Melbourne.

More information

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Control

Herbicide options

See Using herbicides for more information.

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Dicamba 750 g/L (Kamba® 750)
Rate: 5.9 L / ha Use a minimum of 1500 L/ha water carrier. Add a surfactant.
Comments: Boom spray for non-crop situations. Spray prior to flowering.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dicamba 750 g/L (Kamba® 750)
Rate: 400 mL /100 L of water
Comments: Spray prior to flowering. For non crop situations.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dicamba 750 g/L (Kamba® 750)
Rate: 87 mL / 15 L of water. Add a surfactant.
Comments: Spot spray prior to flowering. For non-crop situations.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 10 mL /1 L water
Comments: Spot spray. For general weed control in Domestic areas (Home gardens), Commercial, Industrial and Public Service areas, Agricultural buildings and other farm situations.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
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.
Central Tablelands	Regional Recommended Measure* (for Regional Priority - Prevention) 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.
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.
Western	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.
	*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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Reviewed 2023