Annual ragweed is a herb, 1–2 m tall with fern-like leaves. It causes hay fever, asthma and skin allergies.
Annual ragweed:
Ragweed produces up to a billion pollen grains per plant. The pollen can cause hay fever, itchy eyes, running nose and asthma. Contact with the plant can cause skin reactions including eczema.
Annual ragweed is a shallow rooted annual herb that usually grows 0.5–2 m tall but may be up to 3.5 m tall. Flowering is from summer to early winter.
There are separate male and female flowerheads.
Male flowerheads are:
Female flowerheads are:
Annual ragweed looks like:
Annual ragweed grows along the coast of NSW, mainly north of Sydney. Plants have also been found in the Northern Tablelands.
It is native to North America.
Annual ragweed grows in subtropical and temperate climates. It grows best in warm moist areas and can tolerate a wide range of soil types.
It invades disturbed areas such as roadsides, waste areas, and poor or overgrazed pasture. Horse paddocks in coastal areas are often infested. It also invades floodplains and along the edges of waterways.
Plants produce an average of 3000 seeds per year and seeds can stay dormant for up to 40 years. Seeds can be spread:
Bass, D. J., Delpech, V., Beard, J., Bass, P., & Walls, R. S. (2000). Ragweed in Australia. Aerobiologia, 16(1), 107-111.
Business Queensland (2016). Queensland Government. Retrieved 19 June 2020 fromhttps://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/land-management/health-pests-weeds-diseases/weeds-diseases/invasive-plants/restricted/annual-ragweed
Department of Agriculture and Fisheries, Queensland (2020). Restricted Invasive Plant: Annual ragweed Fact Sheet. Retrieved 12 April from: https://www.daf.qld.gov.au/__data/assets/pdf_file/0006/60666/annual-ragweed.pdf
Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.
PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 19 June 2020 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=gn&name=Ambrosia
Šauliene, I., Veriankaite, L., & Šaulys, A. (2012). Biometrical assessment of ragweed (Ambrosia artemisiifolia L.). Žemdirbyste (Agriculture), 99(3), 319-326.
Weryszko-Chmielewska, E., & Piotrowska, K. (2008). Ecological features of Ambrosia artemisiifolia L. flowers and characteristics of Ambrosia L. pollen seasons in the condition of Lublin (Poland) in the years 2001-2008. Acta Agrobotanica, 61(2).
Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.
Wear appropriate personal protective clothing such as gloves, long sleeves and facemask. Anyone prone to allergies should avoid contact with flowering plants and pollen.
To manage annual ragweed:
Minimise infestations by maintaining healthy, competitive pastures.
Dig out or hand-pull young plants.
Slash or mow young plants before they flower.
Two biological control agents are present in New South Wales. Both of these species were released to control Parthenium weed in Queensland. The stem-galling moth Epiblema strenuana has a reasonable impact on annual ragweed. The leaf feeding beetle Zygogramma bicolorata is more widespread and can have a significant impact at some sites.
Spray plants before they flower. Cover all foliage with herbicide.
See Using herbicides for more information.
Bromacil 800 g/kg
(Various products)
Rate: 3.5 to 6.5 kg per ha
Comments: Industrial weed control: lowest rate suited to lower rainfall areas
Withholding period: Not required when used as directed.
Herbicide group: 5 (previously group C), Inhibition of photosynthesis at photosystem II - D1 Serine 264 binders (and other nonhistidine binders) (PS II Serine 264 inhibitors)
Resistance risk: Moderate
Dicamba 750 g/L
(Kamba® 750)
Rate: 87 mL per 15L 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
Dicamba 750 g/L
(Kamba® 750)
Rate: 5.9 L/ ha. Use a minimum of 1500 L of solution per ha. 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
Dicamba 750 g/L
(Kamba® 750)
Rate: 400 mL per 100L of water. Add a surfactant.
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
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. |
Reviewed 2021