Red witchweed is an exotic weed to Australia and is a serious threat to agriculture.
It’s a parasitic plant that grows attached to the roots of commercially important grasses and cereal crops. These include sorghum, wheat, corn, rice and sugarcane.
Detection in Australia
Red witchweed (Striga asiatica) was detected on a sugarcane property near Mackay, Queensland, in July 2013. Extensive surveillance following this detection identified a total of 8 infested properties.
The Queensland Department of Agriculture and Fisheries (DAF) leads the response to this outbreak.
A response plan has been approved. It covers all aspects of the response including:
- a surveillance and monitoring program
- treatment to eradicate the weedat infested sites
- movement restrictions at high-risk sites and on potential host material
- monitoring after treatment of an infested area to keep it free of red witchweed.
Costs are shared by the Australian and state and territory governments and industry. The Qld government contributes extra resources and funding to the eradication program.
Since 2013 the response program has led to a 99% reduction in red witchweed detections in infested areas.
If you live or work around affected areas in Queensland, look out for this weed. Check your crops regularly for signs of red witchweed, especially if you or your neighbours have travelled or bought equipment overseas.
You must report any suspected sightings.
Report any unusual weeds, even if you’re not sure.
If you live in Queensland and suspect you have found red witchweed you must report it as soon as possible.
You can report using an online form. Or call Biosecurity Queensland on 13 25 23.
Call the Exotic Plant Pest Hotline on 1800 084 881 from anywhere in Australia to report signs of red witchweed.
For signs of exotic pests and diseases in imported goods, sea containers or parcels, call See. Secure. Report on 1800 798 636 or use our online form.
Follow the rules
Keep exotic dangerous pests and diseases out of Australia. Never ignore our strict biosecurity rules.
Import shipments may need to be treated and certified. Before you import, check our Biosecurity Import Conditions system (BICON).
Always check and wash clothes, boots and equipment to avoid spreading seeds.
Do not attempt to remove any flowering red witchweed plants. This may allow the weed to spread tiny, dust-like seeds. Don’t move soil, machinery or products (including mulch) that might contain soil. This will help avoid the spread of seeds to other properties.
Movement restrictions are mandated at infested sites. You must adhere to them. They ensure the weed is not spread further outside the known areas or interstate.
See response activities and movement restrictions in Mackay (qld.gov.au)
About the pest
Red witchweed is an exotic invasive weed and is a parasitic plant which can reduce crop yields by up to 70%. It grows attached to the roots of host plants. These include sorghum, millet, corn, rice and sugarcane. Wheat and barley are also potential hosts.
It is native to tropical and semi-arid Africa, Arabia and Asia. Red witchweed can survive in a range of soils. It does prefer sandy or gravelly soils in tropical or subtropical climates.
What to look for
Red witchweed plants are about 10-40 cm tall and have red, white, yellow or pink flowers. A single plant can produce between 25,000 and 200,000 seeds.
See more at Red witchweed – Identification guide (qld.gov.au)
How it spreads
Red witchweed seeds are tiny and can spread via wind and water. They can be in soil, on vehicles, machinery, clothing and boots. They can also contaminate mulch, fertiliser and plant material.
Red witchweed attaches itself to plant roots. It survives by taking the host’s water and nutrients.
Once affected, host plants may show stunted growth, wilting and yellowing of leaves. These symptoms can be confused for drought damage, nutrient deficiency or disease.
Several of Australia’s trading partners consider red witchweed a quarantine pest. They’ve put conditions in place for a range of our seed and grain exports to address the risk.