Invasive species: weeds, pests and diseases

According to the federal Department of Environment, an invasive species is “a species occurring, as a result of human activities, beyond its accepted normal distribution and which threatens valued environmental, agricultural or other social resources by the damage it cause.

The Australian Government plays a key role in managing environmental biosecurity on a broad level, protecting people and the environment from the negative impacts of invasive species through pre-border preparedness, border protection and post-border management and control.

However, many of the most damaging pests in Australia today were introduced deliberately many decades ago, as food or to counter other problematic species. Others entered inadvertently via produce, plant or animal matter, soil and waste products brought in by people, animals, goods and equipment transported from other regions.

Farmers across Australia invest considerable time and cost in managing these troublesome species – crop-destroying insects and plant diseases, rodents and ‘roos, fruit- and seed-eating birds, soil-degrading rabbits, livestock-ravaging feral cats, dogs and foxes; toxic cane toads, dominant weeds of various species and more. 

The cost of invasive species goes further than crop and stock losses: if not properly managed, diseases, parasites and fungi, insects and other invertebrates, feral animals, weeds and introduced marine pests, have a major negative impact on Australia's environment, threatening biodiversity and reducing species abundance and diversity.

It is crucial that we find effective ways to control invasive species that require the application of fewer (or no) harmful chemicals and enable us to re-affirm Australia’s global status as a supplier of safe, high-quality food.

Organic farming methods, while they can increase some costs, reduce others (such as the cost of pesticides), and may result in ‘cleaner’, safer produce that can command a higher market price.

Weeds

Invasive plants and weeds are a significant threat to our natural environment and to agricultural production, costing Australia around $5 billion annually. Weeds displace native species, contribute to land degradation, and reduce the productivity and hence, the profitability of farms and forestry operations. Controlling them costs time and money.

According to the federal Department of the Environment, “Invasive weeds… have major economic, environmental and social impacts in Australia, causing damage to natural landscapes, agricultural lands, waterways and coastal areas.”

The most cost-effective way to manage weeds is to prevent potential weeds from entering Australia. Once a weed species takes root, it’s crucial to detect and eradicate it quickly.

Research organisations such as Australia’s CSIRO and the University of Melbourne’s Faculty of Science are working on methods for controlling and eradicating invasive plant species while minimising the use of harmful herbicides.

Feral animal control

For farmers in many parts of Australia, managing feral animal pests is an ongoing struggle. Several introduced species, including feral cats, dogs, pigs and camels, rabbits, foxes, fire ants and cane toads, have now endemic to vast regions of Australia. There are also native ‘pests’, such as kangaroos, dingoes, wombats and birds.

Both introduced and native species can cause damage to crops and livestock, if not controlled effectively. There are two main means of managing feral animal pests: conventional and alternative.

Conventional controls

Conventional means of control include fencing, shooting, trapping and baits. Fencing has been widely used in Australia to keep feral animals out – rabbit-proof and dingo fences run for thousands of kilometres across agricultural lands – but for the most part, it is a practical means of feral animal control only on smaller farms; it is difficult and prohibitively costly to fence larger areas effectively.
 
Alternative controls

Biocontrols

Biological controls employ natural predators, parasites, disease-carrying bacteria or viruses to control pests. While some biological control programs have been highly effective in managing invasive species, others have been less so.

The release of the mosquito-borne myxomatosis virus in 1950 to control Australia’s rabbit population killed 90 percent of wild rabbits in the country’s temperate zones in the first six months following its release in 1950, but its uptake in arid regions was inhibited by a lack of mosquitoes; a flea-borne version is proving more successful in these areas.

Scientists are also working on a way to increase transmission of rabbit haemorrhagic disease (RHD, or rabbit calicivirus disease) that has reduced rabbit populations substantially, especially in arid regions, since it became established here in 1995. In recent years rabbits have developed genetic resistance to RHD; a government-funded research program is underway to improve viral strains of RHD in a bid to counter this resistance.

In 1935, an exotic species of toad was introduced to Queensland’s canefields to combat two invasive insect species. This biological control strategy failed on two counts: the cane toads failed to kill the pests and soon, they became a damaging invasive pest themselves.

Guardian animals

On farms across Australia and overseas, trained dogs, alpacas, llamas and donkeys are being used to guard livestock against wild dogs and foxes, reducing the need to use poison baits.

Using ‘guardian animals’ to keep feral predators at bay is an effective method over single farms or small areas, though it does little to address the wider problem of managing these species.

As these animals must be purchased, fed and in the case of guardian dogs, trained, this is a relatively costly option, at least initially, and is generally more suitable for protecting small herds of high-value animals (such as breeding goats).

Innovative pest control              

CSIRO scientists are working on biocontrols to help farmers manage some of Australia’s major weeds and insect pests, including:

  • 'classical biocontrols’, in which farmers introduce exotic invertebrates to control exotic invertebrate pests and weeds, and
  • 'conservation biocontrol', in which beneficial invertebrates already present are encouraged and augmented.

Sensor technology and species sterilisation are being trialled by CSIRO as a means of controlling the crop-damaging Queensland fruit fly.

The Grains Research & Development Commission (GRDC) has various genetic breeding programs underway with the aim of increasing grain crops’ resistance to problematic pests and diseases.

Managing biodiversity to help control invasive species is beneficial to both crops and the environment. CSIRO is looking at certain species of native vegetation that may play an ‘ecosystem service’ role in pest management, reducing the need for pesticides.

Other sustainable farming methods, such as companion planting, can also reduce the need to use potentially harmful chemicals on key crops.

In northern NSW, local horticulturalists, along with Industry & Investment (I&I) NSW entomologists at Alstonville, are looking at “a holistic approach to managing fruit spotting bugs through biological control, improved pest monitoring using lures and traps, companion planting and ‘soft’ sprays”,  with research to date indicating that horticulturalists “can reduce the use of chemical sprays significantly and achieve sustainable long-term control with this new approach”.

Further information

Australian Government Department of Environment’s invasive species policy
http://www.environment.gov.au/biodiversity/invasive-species

Department of Environment publications regarding invasive species
http://www.environment.gov.au/biodiversity/invasive-species/publications

Australian Government Department of Agriculture, Fisheries and Forestry (DAFF) on environmental biosecurity
www.daff.gov.au/animal-plant-health/pihc

Queensland Government Department of Agriculture, Fisheries and Forestry (DAFF) resources on pests, weeds and feral animals
http://www.daff.qld.gov.au/plants/weeds-pest-animals-ants/educational-resources-and-careers/publications  

Grains Research & Development Commission (GRDC) genetic breeding programs
http://www.grdc.com.au/Research-and-Development/Project-Summaries/Theme-3

CSIRO biocontrol projects
http://www.csiro.au/Outcomes/Food-and-Agriculture/Managing-insect-pests-and-weeds.aspx

CSIRO research into Queensland fruit fly
http://www.csiro.au/Outcomes/Food-and-Agriculture/Managing-insect-pests-and-weeds.aspx

CSIRO research into ecosystem service role of native species
http://www.csiro.au/Outcomes/Food-and-Agriculture/CapturingEcosystemServices.aspx

University of Melbourne Faculty of Science research into invasive species
https://science.unimelb.edu.au/weeds-invasive-plants

NSW Department of Primary Industry on organic farming methods
http://www.dpi.nsw.gov.au/agriculture/farm/organic

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