NRM top tips - March: Control invasive weeds and pests

Since European settlement many plants and animals have been introduced to Australia, many of which have spread and multiplied becoming significant agricultural and environmental problems.

It's estimated that invasive species cost Australia billions of dollars annually in reduced agricultural outputs, and management, administrative and research costs. Invasive species are damaging and decimating native ecosystems and wildlife across Australia through predation, habitat destruction, disease and competition for resources such as food and shelter.

Controlling invasive species is often not easy and can be time consuming and costly with total eradication in many cases not feasible. However, there are a couple of key principles fundamental to invasive species control that have proven to be effective.

Preventative methods focus around risk management and early intervention. Understanding what is native on your farm and then mapping and continually monitoring known invasive species can be a useful tool for being prepared to act when new species are detected. Government biosecurity and local council or natural resource management group websites are a good resource for understanding what species may be potential new threats to your farm. Practicing good farm hygiene can also play an important role in preventing the establishment of new invasive species, particularly weed seed.  Ensure tools, boots, equipment and machinery are clean when moving around the farm.

The most effective approach towards containment of established invasive species is an integrated approach undertaken with surrounding land managers (private & public) and using a number of different control techniques over time. It is also important to monitor and evaluate over time the effectiveness of any invasive species control program implemented on your farm.

There a number of different strategies in addition to those already described that can be effective in the management of weeds and pests in natural areas, such as:

Weeds

• Minimise soil disturbance to prevent seeds buried in the soil from coming to the surface.
• Minimise traffic in areas where weeds are established and avoid if possible, during periods when weeds are shedding seeds to reduce spread to other areas of the farm.
• Target your control efforts at smaller populations in better condition natural areas or those areas that have a higher value to you.
• Reduce the potential of re-establishment of weeds post removal. Post removal conditions, depending on control technique, can often provide favourable conditions for re-establishment through increased space, light and in the case of fire control higher nutrients. Before removal have a plan for continued control and restoration.

Pest animals

• Focus on protection of priority natural assets/areas that may be in better condition or have a higher value to you.
• Use best practice techniques that consider interactions between species, accounts for seasonal conditions (e.g. pest animal congregations during droughts) and animal welfare.
• Management of mobile pest animals requires a co-ordinated approach across a range of scales and land tenures.

Andrew Watson (pictured) and his mother Robyn have been taking on the challenge of riparian weed management for over four decades - successfully controlling weeds such as willows along a reach of the Namoi river near Boggabri. Their long term commitment to weed management and riparian restoration has seen them receive a number of local and state Landcare awards.

More recently Andrew has been tackling the challenge of weed control along Maules Creek in north western NSW. In 2016, Andrew and his wife Heike brought the property “Merriendi” a 990ha irrigation and dryland farm with approximately 10km of riparian corridor along Maules Creek.

“When we brought the farm just over two years ago, the riparian corridor was inundated with Green Cestrum which is toxic to stock and is listed as a noxious weed in our local council area. The Green Cestrum was so thick along the creek we were unable to get down to the creek in some areas,” Andrew said. 

Working with the local council and his neighbours Andrew undertook a two-year program of weed control which involved the implementation of a range of chemical and physical control techniques.

“Firstly we had to clean away a number of old fences and flood debris to enable us to access all areas of the creek banks.  Then we were able to use chemical control measures over a number of years to kill the cestrum,” Andrew said.

Andrew has now managed to get the Green Cestrum under control and has been able to reclaim their riparian corridor as well as some cropping country that the previous owner had fenced off due to encroachment of cestrum.

“To prevent re-establishment of the cestrum, as well as other weeds, we continually monitor the area so we can respond quickly,” Andrew said.

"We have also introduced conservation grazing techniques as stock can be an effective management tool when used appropriately as they help to trample down vegetative matter producing a litter load which reduces sunlight and the opportunity for weeds to establish."

Andrew believes resting the area when the native species are most likely to set seed is responsible for the regeneration that is now evident along the creek.

“In the future we may consider revegetating parts of the creek, especially where the river red gums appear to not be regenerating which UNE researcher Dr Rhiannon Smith believes may be a result of their age and lack of reproductive seeds."