Red witchweed

Alert

Have you seen Red witchweed?

Be on the lookout for Red witchweed and report it to Biosecurity Queensland. Early detection and reporting are the key elements in controlling Red witchweed.

Call us on 13 25 23.

Native to tropical and semi-arid Africa, Arabia and Asia, red witchweed is a parasitic plant that grows attached to the roots of certain grasses. Hosts of red witchweed include commercially important grasses and summer cereals such as sorghum, corn (maize), rice and sugar cane. It can also be found growing on a wide range of tropical grasses common on headlands and in pastures.

Red witchweed causes an estimated $7 billion of damage to grain crops in Africa each year.

Red witchweed is a prohibited invasive plant under the Biosecurity Act 2014.

Scientific name

Striga asiatica (Syn. S. Lutea, S. hirsuta)

Similar species

Description

  • Parasitic plant attached to roots of host, grows 10-40cm above ground.
  • Leaves are 6-40mm long, 1-4mm wide, with tapered, pointed tip, arranged in opposite pairs along stem.
  • Flowers are 5-20mm long, usually red, sometimes white, yellow or pink.
  • Seeds are very small.

Habitat

  • Prefers semi-arid savannas and grasslands, generally in tropics and subtropics, but can persist in warm temperate areas where suitable hosts exist.

Distribution

  • Occurs in 1 population found near Mackay.

Life cycle

  • Seeds only germinate in close proximity to roots of suitable host.
  • Seeds remain viable in soil for up to 15 years.

Impacts

Economic

  • Affects corn (maize), millet, rice, sugar cane and sorghum.
  • Has potential to become serious pest.
  • USA has spent more than $250 million on eradication in Carolinas.
  • In Africa, heavy infestations can reduce grain crop yields by up to 70%.

How it is spread

  • Seeds spread primarily within soil (which can adhere to machinery or vehicles or other contaminated produce such as mulch or seeds).
  • Seeds can be a contaminant of imported grain, pasture seeds or organic fertiliser, or present in soil adhering to imported machinery.

Control

  • Call 13 25 23 if you find a plant you suspect may be red witchweed to seek advice on control options.

Legal requirements

  • Red witchweed is a prohibited invasive plant under the Biosecurity Act 2014.
  • It must not be kept, moved, given away or sold without a permit.
  • The Act requires that all sightings are reported to Biosecurity Queensland within 24 hours.
  • By law, everyone has a general biosecurity obligation (GBO) to take all reasonable and practical steps to minimise the risk of red witchweed spreading until they receive advice from an authorised officer.

Further information