Pest & Weed Control

Pest animal control

There is an increased window of opportunity to control pest animals post fire, as their food source has been disrupted.

Rabbits

Fire removes groundcover, so there is an opportunity to map where burrows exist. A baiting program is appropriate for large numbers. A warren ripping and fumigation program should follow. Generally one activity by itself is insufficient to control rabbits and vacant warrens will eventually be reinhabited. DPI has assisted with this work following major fire events.

Information Notes:

LC 0296: Rabbit control using Pindone poison (VIC)

LC 0295: Rabbits: Methods of fumigating rabbit burrows (VIC)

LC 0297: Rabbits: Warren destruction and harbour management

Foxes

Foxes are controlled by baiting, shooting, fumigating and destruction of dens. The integrated use of several methods will enhance control. Fox control following summer fires is particularly important for autumn lambing. For spring lambing, control can be left to mid year. Baiting is undertaken using 1080 poison and a chemical user’s permit (ACUP) is required with a 1080 endorsement to undertake this work. A program coordinated with neighbours is likely to be more effective. DPI has coordinated and financed such programs after major fire events. Information Note LC 0302: Integrated fox control

Weed management

Impact on weeds

The risk of weed invasion and the impact on farms and the environment dramatically increases during and after wildfire. After the 2003-04 bushfires in eastern Victoria, new weed species were identified and an increase in the number of infestations of existing weeds was observed. Immediate impacts of weed invasion after fire are not only felt in the areas burnt but also throughout the landscape, where weeds have been dispersed by vehicles, humans, fodder, stock and even water.

Bushfire brings with it two processes that can potentially increase the rate of weed invasion. One relates to the creation of a window of opportunity for competitive exotic plant species after fire. These species will take advantage of extra light, space, nutrients and moisture caused by the absence of desirable plants such as native vegetation, crops or pasture. Desirable species may also be vulnerable to pest species such as selective grazing on new growth by rabbits.

The other process relates to weed spread as a result of fire suppression, fire recovery and environmental events.

Fire suppression

• Fire ground vehicles carrying weed propagules (seeds, stems and bulbs) can spread weeds. Weed propagules can be dislodged or picked up on the fire ground and dispersed by vehicles and machinery such as bulldozers. Humans can accidentally spread weed propagules on socks, boots and clothing.

Fire recovery

Weed propagules can be:

• imported in fodder onto farm
• blown from vehicles transporting fodder
• imported on or in replacement or agisted stock
• brought in by vehicles and equipment of contractors and advisers replenishing water supplies, rehabilitating fire breaks, clearing fence lines and re-establishing vegetation
• spread in seed, mulch, soil and rock used in rehabilitation programs.

Environmental events

Weed seeds can also be easily spread by water flow across bare ground during rain. Once ground temperature gets above 200° Celsius, the organic matter vaporises and makes the soil resistant to water (hydrophobic). Higher run-off rates not only cause erosion and siltation of waterways but aid the dispersal of weed seeds further down the catchment.

Seeds from desirable species, as well as weed seeds, may be blown from bare ground burnt by moderate intensity fire. This can leave areas more susceptible to new weed invasions with more weed seed deposited by wind.

Weed spread after wildfire

Natural ecosystems

Bushfires often burn areas of exotic weeds that were posing a significant threat to forests and natural ecosystems. Weeds quickly re-establish after fires often germinating more quickly than native species. Bushfires can exacerbate the growth of opportunistic weeds such as English Broom, Blackberry and St Johns Wort.

Bushfires can present an opportunity to gain access into areas to tackle these weeds. Integrated weed control programs can focus on minimising the threats to key conservation values, infestations impacting on neighbours and eradicating isolated pockets.

Weed management before, during and after wildfire

There are many strategies to minimise weed establishment and spread during and after fire.

Before and during fire:

Knowing where weed infestations are or have been (mapping) enables a quick response for surveillance, leading to control and prevention of the spread of weeds. It may be beneficial to establish strategic vehicle and machinery wash-down areas for fire vehicles and other machinery that need to work in high-risk weed spread areas.

After fire:

• Verify your weed mapping and step up surveillance for new weed outbreaks. Perennial weeds with well-established, deep root systems survive fire very well. Weeds such as flatweed, docks, sorrel and onion grass are the first plants to recover and are often prominent after fires.
• Check the origin of your fodder. Has it come from a known weed infested site? Keep records of where fodder is purchased.
• Feed out fodder in a confined area (stock containment areas), away from drainage lines to reduce the likelihood of weeds being spread.
• Monitor the feed areas regularly and be suspicious of unfamiliar plants.
• Identify suspect plants as soon as possible.
• When building up stock numbers or accepting agisted stock, quarantine them for 14 days allow time for viable seed to pass through the animal.
• Check for weed seeds in fleece and continue to check for weeds in areas with new stock.
• Monitor stock routes and roads for up to 12 months after fire to detect new weeds.
• Ensure vehicles and equipment of agencies, contractors and advisers are clean and free of weeds before entering and leaving your property.
• Seed, mulch, soil and rock to be used for rehabilitation programs should be free of weed seed and propagules.
• Increase integrated weed control treatments - the first two years are critical.

Re-vegetation work must go hand in hand with treatment.