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Witch weeds
Pest alert
If you have seen this plant
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- Witch weeds flowers
(Photo courtesy of Dr Rebecca Nelson)
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- Witch weeds infestation
(Photo courtesy of CIMMYT)
General information
Witchweed is a common name loosely applied to up to 30 different species within the genus Striga. All species of witch weed are small, parasitic herbs. Three species are major pests of grain crops in Africa, where they cause an estimated $7 B damage each year. Invasive species risk assessment presents evidence that non-native witchweeds have the potential to become costly pests in Queensland. Non-native witchweeds are currently absent from Queensland and there is an opportunity to prevent their naturalisation. Several species of witch weeds srank as some of the world's worst weeds of agriculture.
Biosecurity Queensland encourages people report this Class 1 pest plant and take actions to help stop the establishment, prevent the spread, and to control this pest.
Overview
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Scientific name |
Striga spp. |
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Description |
- Grows to about 30cm.
- Leaves are between 6-40mm long and 4 mm wide and have a tapered pointed tip.
- Flowers are 5-8mm long.
- Flowers vary from red, pink, white, yellow, orange or purple.
- Some species only emerge from below ground to flower (hence the name 'witchweed').
- Five-sided capsule fruit 4mm long and 2mm wide.
- Seeds are very small and can persist for 15 years.
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Habitat |
- Prefers semi-arid savannahs and grasslands, generally in tropical areas but sometimes subtropical and warm temperate areas.
- Grows on roots of other plants.
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Distribution |
- Generally native to semi-arid, tropical areas of Africa, but have been recorded in more than 40 countries.
- Not known to exist in Australia.
- Non-native Striga species are currently absent from Queensland but have the potential to affect significant areas.
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Life cycle |
- Seeds only germinate in close proximity to the roots of a suitable host.
- Seeds remain viable in soil for up to 15 years.
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Spread |
- Seeds spread by wind, water, soil movement, sticking to feet, fur or feathers.
- Seeds could be a contaminant of imported grain/pasture seeds or within soil adhering to imported machinery.
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Impacts |
Economic
- Heavy infestations can reduce grain crop yields by up to 70%.
- Can cause export grain to be rejected.
- Effects maize, millet, legume crops, rice, sugarcane and sorghum.
- Has the potential to become serious pests if introduced or cultivated as ornamentals.
- United States has spent more than $250 million on eradication from the Carolinas.
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Prevention |
The best form of weed control is prevention. Treat weed infestations when they are small - do not allow weeds to establish.
Steps for weed prevention:
- Check your property regularly for suspect plants.
- Control new infestations before they spread and become a major problem.
- Don't dump weeds and garden waste in bush or parkland.
- Know the weed status of any products or materials you are receiving. This includes fodder, grain, gravel, machinery, mulch, packing material, sand, soil, stock, vehicles and water.
- Clean your equipment, clothing, shoes, vehicles and machinery when leaving natural habitats and camping areas.
- Use a cleandown facility to blow, vacuum or wash dirt and seeds from vehicles, machinery and tools.
- Request a weed hygiene declaration from your suppliers.
- Ensure vehicles and machinery are clean before entering your property.
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Declaration details |
- A declared Class 1 species under the Land Protection (Pest and Stock Route Management) Act 2002.
- Not commonly present or established in Queensland and has the potential to cause impacts to whole or part of the State.
- Introduction, keeping, releasing and supplying (including supplying things containing reproductive material of this pest) is not possible without a permit, for special purposes, issued by Biosecurity Queensland.
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Further information |
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Page maintained by Sonia Jordan
Last updated 07 February 2013
