Witchweed
Alert
Have you seen Witchweed?
Be on the lookout for Witchweed and report it to Biosecurity Queensland. Early detection and reporting are the key elements in controlling Witchweed.
Call us on 13 25 23.
Purple witchweed flowers
© Jayesh Pail Creative Commons
Red witchweed
© Ton Rulkens Creative Commons
Cowpea witchweed
© Ton Rulkens Creative Commons
Striga in sorghum
© ICRISAT Creative Commons
Striga white flower
© Bahamut Chao Creative Commons
Native to semi-arid and tropical Africa, and recorded in more than 40 countries, 'witchweed' is a common name loosely applied to up to 30 different species in the genus Striga. All witchweed species are small, parasitic herbs. Three species are major pests of grain crops in Africa, where they cause an estimated $7 billion damage each year. Witchweed species rank as some of the world's worst agricultural weeds.
Non-native witchweeds are currently not found in Australia but have the potential to become costly pests in Queensland. An opportunity exists to prevent their naturalisation here.
You must take reasonable action to minimise the risk of spreading Witchweed to ensure the situation isn't worsened.
You must report all sightings to Biosecurity Queensland within 24 hours.
Scientific name
Other names
- Parasitic witchweeds
Similar species
Description
- Herb up to about 30cm tall.
- Leaves are 6–40mm long, 4mm wide, with tapered pointed tip.
- Flowers are 5–8mm long.
- Flowers can be red, pink, white, yellow, orange or purple.
- Capsule fruit are 5–sided, 4mm long, 2mm wide.
- Seeds are very small, can persist for 15 years.
Habitat
- Prefers semi-arid savannahs and grasslands, generally in tropical areas but sometimes subtropical and warm temperate areas.
- Grows on roots of other plants.
Distribution
- Non-native Striga species are currently absent from Queensland but have the potential to affect significant areas.
Life cycle
- Seeds only germinate in close proximity to roots of suitable host.
- Some species only emerge from below ground to flower (hence name 'witchweed').
- Seeds remain viable in soil for up to 15 years.
Impacts
Economic
- Heavy infestations can reduce grain crop yields by up to 70%.
- Causes export grain to be rejected.
- Affects maize, millet, legume crops, rice, sugar cane and sorghum.
- Has the potential to become serious pest if introduced or cultivated as ornamentals.
- USA has spent more than $250 million on eradication from the Carolinas.
How it is spread
- Seeds spread by wind, water, soil movement, feet, fur or feathers.
- Seeds could be contaminant of imported grain/pasture seeds or in soil adhering to imported machinery.
Prevention
Control
- Before undertaking any preventative or control actions, contact our Customer Service Centre.
Legal requirements
- Witchweed is a prohibited invasive plant under the Biosecurity Act 2014.
- You must not keep, move, give away, sell or release into the environment. Penalties may apply.
- You must not take any action reasonably likely to exacerbate the biosecurity threat posed by witchweed.
- You must take any action that is reasonably likely to minimise the biosecurity threat posed by witchweed.
- You must report all sightings to Biosecurity Queensland within 24 hours.