The Association runs, or contributes to a number of weed programs annually with a 79% increase allocated to those programs since 2014. These programs are focused on significant weeds that are still located over relatively small areas such as prickly acacia and mesquite. They were selected based on the likelihood that if funds were allocated to their control it would be beneficial to the whole of the Kimberley longer term. The four weeds the Association currently contributes to are -
Currently these weeds are restricted to just a single or few locations and have been assessed as weeds that could potentially be eradicated from those location/s.
The target weeds in the Association’s current programs all met the following assessment criteria to qualify –
(Important note. Mimosa bush (Vachellia farnesiana) is a widespread plant in the Kimberley that looks like and is often called prickly acacia, however its thorns are generally much smaller and there are small differences in both general plant appearance.
Prickly acacia is a Weed of National Significance and is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. At present over 6.6 million ha of Queensland is infested and it’s found in scattered populations across the NT with a substantial infestation in the southern Victoria River district.
It is a thorny, spreading tree generally growing to about 4–5 m high and occasionally to 10 m. A pair of stout spines, 10–50 mm long, grows at the base of each group of leaves in young stems. Flowers are yellow, fluffy round clusters 10 mm in diameter. Seed pods are grey-green, covered in fine hairs and generally 100–200 mm long. Seeds may be washed downstream in fast flowing water, but long distance spread in Australia is mainly attributed to consumption of seeds by animals such as cattle.
There are only two sites known in WA, both in the East Kimberley with the smaller been controlled by the land-manager. The larger site covers in excess of 10,000 hectares. The Association started its work program on this site late 2010 following on from a previous program lead by DAFWA that started in 2006. In that first year (2010) nearly 10,000 plants were controlled. In the 2018/19 wet season when control occurs the number of plants found and controlled totaled 80.
This work remains ongoing and eradication is expected to be attained within ten years.
Mesquite is a Weed of National Significance and is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. There are four species and several hybrids of the weed, which are all collectively known as mesquite currently in Australia. It is widespread across northern Australia particularly in Queensland. The Mardie Station infestation (150,000 ha) in the Pilbara is the largest single core infestation in Australia.
Mesquite’s economic impacts stem from its ability to form impenetrable thickets which, combined with its large thorns, prevent stock accessing watering holes and make mustering difficult. Mesquite also reduces the productivity of pastoral country by taking over grasslands and using valuable water resources.
Mesquite leaves are fern-like, occurring in groups of one to three pairs, often with one or two thorns up to 50 mm in length. The greenish cream–yellow flowers resemble a ‘lamb’s tail’, 50–80 mm in length. The seed pod (up to 200 mm long) is straight or slightly curved. The bark is smooth and dark red-green in young stems, and rough and grey in older stems. The taproot is large and much branched and generally grows to a depth of 20 m. Identification of mesquite is complicated because there is often variation in growth form, even within the same species, and hybrids (or crosses) between the main species.
The combination of a long life cycle, ability to survive droughts, high seed production and dormancy of its seeds makes mesquite an extremely resilient invader which can quickly take advantage of a suitable environment and dominate entire ecosystems.
There are two main mesquite sites in the Kimberley, one in the east and the other in the west Kimberley, the West Kimberley infestation is spread over approximately 8,000 hectares and the East Kimberley infestation 16,000 hectares. There are plans to try and introduce a biological control into the West Kimberley infestation in 2019 whilst it is already established at other site for a number of years and working successfully.
The Association started its work program on the East Kimberley site in 2012 following on from a previous program lead by DAFWA. In that first year nearly 6,000 plants were controlled. In the 2018/19 wet season when control occurs the number of plants found and controlled totaled 75. This work remains ongoing and eradication is expected to be attained within ten years.
Rubber vine is a Weed of National Significance and is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. Its main impact on pastoralism is the loss of grazing country, which in 1995 was estimated to cost the Queensland beef industry $18 million. It also increases the costs of mustering and fencing. Rubber vine has a potential distribution covering all of northern Queensland, the northern half of the Northern Territory, and most of the Kimberley region. The total area of rubber vine infestation in Queensland was estimated at over 700,000 hectares but was present in an area 50 times as large.
Rubber vine is a many stemmed shrub which can climb 30 m into tree canopies. The stems are greyish brown with a smooth bark. A typical trait is the formation of a ‘whip’ that extends itself onto nearby adjacent vegetation. The plant exudes a milky sap if scratched or broken. The leaves occur in pairs and are a glossy dark green in colour. The trumpet shaped flowers are quite large, up to 50 mm long and wide, with five light purple to white petals. The seed pods are rigid and usually occur in opposing pairs at the end of short stalks, up to 120 mm long and 40 mm wide. Roots can grow to a depth of 12 metres.
There are two significant infestations in the Kimberley, one present on the top end of Lake Argyle in the East Kimberley and another along the Fitzroy River in the West Kimberley. Both of these infestations are being controlled by partnership groups involving the land holders, state agencies and the Association.
Gamba grass is a weed of National Significance and is regarded as one of the most significant threats to northern Australia because of its invasiveness, potential for spread, and economic and environmental impacts. It is a large perennial grass up to 4 m tall with tussocks up to 70 cm in diameter. Its leaves are 30-60 cm long, up to 3 cm wide, covered in soft hairs, with distinctive white midrib, stems are robust and covered in soft hairs. Seeds are contained in fluffy V-shaped seed head consisting of up to 6 groups of branches, each containing 2-18 primary branches.
Gamba grass currently affects up to 15,000 square kilometres of the Northern Territory, but has the potential to affect a further 380,000 square kilometres with most infestations currently north of Katherine. There is also estimated to be a total of 60,000 hectares spread across Queensland's north.
It was introduced into Australia in the 1930s, trials were conducted at the Katherine Research Station from 1946 specifically for use as a cattle fodder. Since that time it has proved to be highly invasive with the ability to negatively impact on savanna landscapes in northern Australia. It is now seen to be a serious bushfire threat as it carries up to eight times higher fuel loads than native forest and pastures. As a result bushfires are extensive with increased intensity affecting tree canopy and transforming woodlands to grasslands. It also poses a serious threat to people and property. Where gamba grass continues to be used as a fodder, it requires careful management to maximise productivity, limit seed production and control spread.
There is one known infestation in Western Australia. It is situated in the East Kimberley and covers 433 hectares. Work on this site is being undertaken by a partnership group involving the land holders, state agencies and the Association.
Weed subsidies are available to all land holders within the area managed by the Kimberley Rangelands Biosecurity Association who pay annually the Declared Pest Rate. The rate is determined on property value and is raised to fund the control of established declared pests.
Currently the amount a land manager can claim per lease is up to $10,000 and is payable for the purpose of the purchase of chemicals and the use of registered and licenced contractors to carry out the control.
The following conditions apply to the subsidy
Regarding providing proof of chemical or contractor use there are a number of methods that could be used. It is extremely important that anybody considering applying for the subsidy contacts a staff member before to discuss the options so they can be agreed on prior to any purchase or application. Examples of what have been used in the past include –
Please note that random audits of the work done will be undertaken annually for verification purposes.
