Combatting weed spread when disaster strikes
24 February 2022
Flood, fire and drought all clear a path for opportunistic pest plants. Find out what you can do to help prevent their spread.
Severe weather events are the reality of a changing climate in South Australia. What’s less obvious is the impact of invasive weeds in their aftermath.
They may not be the first priority following a natural disaster but early vigilance could save a second blow – a costly weed burden.
Weeds cost us all
There are more than 2,700 established weeds in Australia, with nearly 500 declared as requiring legislative control.
They threaten the country’s unique biodiversity, fuel fires and cost Australian agriculture an estimated $4 billion annually.
Flood waters become weed highways
Weeds are innately good spreaders in the Australian landscape, thanks to their prolific seeds, high adaptability and lack of natural predators, like insects and diseases. They also take advantage of natural transport like wind and water.
During flooding, water can carry seeds long distances to new locations.
This is a particular concern with the highly invasive weed buffel grass on flood-affected Eyre Peninsula and in the state’s north.
Buffel grass plants are rapid spreaders, aggressively invading riparian and arid environments, outcompeting pastures, displacing native habitat and threatening Aboriginal cultural heritage.
They colonise quickly after summer rain, setting seed within six to eight weeks, and each plant produces thousands of heat and moisture tolerant seeds that can remain viable for up to seven years.
Land managers are urged to be on high alert for unfamiliar plants that turn up in unexpected locations.
Fire can help weed seeds germinate
While very hot fires sterilise the soil, cool-to-moderate and hot burns can stimulate plant seeds to germinate.
This is the case for many invasive weeds that subsequently thrive on the bare ground and present a costly challenge to land managers across the state.
Four things you can do to prevent weed spread after a natural disaster
1. Keep your eye out for suspicious plants
Prevention is better than cure. Move quickly when you spot a suspicious plant.
Your local landscape board can help correctly identify the species and then provide advice about the most effective treatment options for your situation.
2. Ramp up on-farm hygiene
Vehicles contaminated with weed seeds is one of the most common ways weeds are spread.
This makes on-farm hygiene important at any time, but it’s particularly critical post-fire or during a drought, when there is little groundcover to outcompete weeds.
3. Monitor stock feeding areas
Weed seeds can also sneak onto a property in hay or feed stock often used during tough times.
Feed in a confined stock area to reduce the likelihood of weeds spreading throughout the property and monitor feeding areas for any weeds that germinate.
4. Make a fresh start after fire
Fire can present an opportunity to stamp out weeds on your property, as it reduces the amount of plant matter in weed infestations.
Control any regrowth and replant bare ground with appropriate cover.
Want to know more?
The Department of Primary Industries and Regions' Weed Control Handbook for declared plants in South Australia is a handy resource.