Broomrapes (Orobanche species)

PROHIBITED MATTER: If you see this plant report it to the NSW Invasive Plants & Animals Enquiry Line 1800 680 244

Profile

Impact

Broomrapes are parasitic plants that are among the world’s worst crop weeds. They pose a serious threat to broadleaf grain and vegetable industries in Australia. Once established, broomrapes can reduce crop yields by up to 70%, threaten export markets and be extremely difficult to eradicate.

Broomrapes attach to the roots of broadleaf plants and extract all of their nutrient and water requirements from their host. In Australia, known host plants include canola, carrot, lettuce, tomato, capeweed, vetch and medics.

Branched broomrape (Orobanche ramosa) poses the greatest threat to Australian crops and is only known to occur as an isolated infestation in the Murray Bridge area of South Australia. No known infestations of branched broomrape occur in New South Wales (NSW).

Other species of concern are Egyptian broomrape (O. aegyptiaca), nodding broomrape (O. cernua var. cernua), crenate broomrape (O. crenata) and sunflower broomrape (O. cumana), none of which currently exist in Australia.

Native broomrape (O. cernua var. australiana) and another exotic, clover broomrape (O. minor), are present but not considered a problem.

Distribution

Worldwide there are approximately 140 species of broomrape. Branched broomrape is native to southern Europe, western Asia and northern Africa and is considered a weed in its native range.

Five species of broomrape are major crop weeds throughout northern Africa, the Middle East, Europe, Asia and America.

Spread

Broomrapes are annual plants that grow from seed and require a host plant to survive. After a broomrape seed germinates, the seedling’s roots attach to the roots of a host plant and the whole broomrape plant remains underground until its flowering stems emerge (about 6 weeks after germination). Flowering and seed set occurs within 2–3 weeks. One plant can produce thousands of seeds per year which can lay dormant in the soil for many years.

Broomrape seed can be spread by wind, livestock, vehicles, clothing, flood waters and contaminated fodder, seed and soil.

Description

A characteristic of all broomrapes is they contain no chlorophyll and only the flowering stem can be seen above the ground.

Key identification features

  • Stems are up to 30 cm high and densely branched from ground level. Brown or straw-yellow in colour and covered with soft woolly hairs.
  • Very few scale-like leaves occur at the base of the stem and are up to 8 mm long.
  • Flowers are 1–2.2 cm long, trumpet-shaped and pale-blue to violet in colour. Flowering occurs in summer.
  • The fruit is a single-celled capsule containing hundreds of seeds. The capsule dries and shatters in summer.
  • Seeds are about 0.3 mm long, oval in shape, have a rough surface and are black, brown, or yellowish-brown in colour.

Acknowledgements

2009 edition prepared by Rachele Osmond; 2013 edition reviewed by Michael Michelmore; edited by Elissa van Oosterhout.

References

Faithfull I & McLaren D (2004) Branched broomrape – identification: State prohibited weed. Landcare Note LC0272. State of Victoria, Department of Sustainability and Environment

Hosking JR, Sainty GR, Jacobs SWL & Dellow LL (in prep) The Australian WeedBOOK

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Control

If you suspect you have found any form of broomrape, immediately contact a local council weeds officer who will assist with identification, removal and eradication.

Herbicide options

Contact your local council weeds officer for control advice for Broomrapes (Orobanche species).

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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 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 Prohibited Matter
A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries
All species of Orobanche are Prohibited Matter in NSW, except the natives Orobanche cernua var. australiana and Orobanche minor

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2017