The ABI Alien Clearing Project


Invasive alien plants have been highlighted as one of the biggest threats to the Agulhas Plain, and the broader Overberg. Studies have found they cost the Cape Floristic Region around R700-million every year. The Plain itself is 23 percent invaded by alien species - resulting in the loss of economic development (for example job creation through flower harvesting), and threatening this globally-acclaimed biodiversity hotspot. 

Clearing invasive aliens is an expensive business, making it a challenge for many private land users to ensure their lands are completely free of invasive plants. A further challenge is the lack of coordination between stakeholders involved in alien clearing. As an example, a landowner who clears his land could find his property re-infested by a neighbour who is not interested in alien clearing. As it is, alien clearing resources are scarce - and we therefore cannot let alien-clearing funding go to waste in such a way. 


That’s why funding secured from the Department of Environmental Affairs (DEA) in 2013 for invasive alien clearing activities on the Agulhas Plain was so important, as it allowed clearing activities to take place strategically, over a larger area. The funding came from DEA’s Land User Incentive Scheme, and amounted to R18-million over the next three years. Partners involved in the project, including land user groups and NGOs, were responsible for co-funding the project.


So, in 2013, the ABI Coordination Unit (coordinated by Flower Valley Conservation Trust) hosted the first meeting to bring stakeholders together. This grouping decided on the project model and rollout, and from here, representatives were selected from land user groups who wished to be involved (conservancies, farmer’s associations etc), to stand on an Implementation Committee. Municipal officials, and officials from CapeNature and SANParks were also elected to stand on this committee, to provide vital input and assistance. 


This committee initially met frequently, to together develop and plan the implementation of the project. Once the planning had been finalised, nine land user groups agreed that they wished to participate in the project, covering an area of approximately 100,000 hectares on the Agulhas Plain - much of this consisting of significant fauna and flora. About 100 landowners were therefore included in the project, while around 250 jobs were created for project participants. The committee also decided to focus on follow-up in the initial years of the project, and to focus on clearing natural vegetation (with agricultural lands excluded).  


Currently work in the ABI Alien Clearing Project continues, with approximately 30,000 hectares cleared per year. The project works with 28 contractors, who employ their own teams. These contractors and their teams have also been vital in planning the work to be undertaken, as their experience in the first year provided essential information on the densities of areas to be cleared, and some of the practical challenges in the field. 


It’s hoped that alien clearing activities will not be halted after just three years - which would threaten all the gains made in the first three years of the project. As such, the ABI Alien Clearing Project is looking at ways to support clearing activities here for the next 20 years. And those partnerships built up, with land user groups, landowners, contractors, their teams, other government partners involved, and vital donors such as DEA, the Drakenstein Trust and Hans Hoheisen Charitable Trust, will prove essential in the long run.     

For more information, contact Roger Bailey: Tel. 028 388 0713, or email:

Tackling the Invasives


Clearing methods depend on the invasive alien species. Here is a breakdown of some of themost successful clearingmethods on some of themost common invasive alien plants found in the Overberg.


A full list of invasive alien plants

Black Wattle


Seedlings: These can be hand-pulled, or plants up to a metre tall can be treated with foliar spray. Up to 2m tall plants can be treated with spot spray.

Mature trees: Trees can be felled, but stumps smaller than 20cm must be treated with herbicide. Frilling will also work, as trees will die if cuts are made into the cambium. Apply herbicide. Ringbark mature trees by removing a 10cm wide strip near the base of the trunk, and apply herbicide.

Burning: Dense stands can be burnt, but note that fire stimulates the seed bank, so follow-up is essential.
Biological control: Fungus can be applied to the stumps.

Port Jackson

Seedlings: These can be hand-pulled or hoed, or can be removed by using a tree popper. Saplings can also be treated with foliar spray.
Mature trees: Large trees should be felled as low as possible, with the stump treated with herbicide. Large trees can also be removed through frilling, with trees treated with herbicide.
Burning: Fire stimulates the seed bank of Port Jackson, so burning should be approached with care.
Biological control: The gall fungus was released on the Agulhas.



Seedlings: These can be hand-pulled, and saplings can be treated with a foliar spray such asGarlon.Young trees should be cut low to the ground.
Mature trees: Large trees should also be felled low to the ground.
Burning: Fire can be used to kill medium to scattered seedlings.However, thismust be done in an ecologically acceptable manner – and therefore not too frequently.
Biological control: A seed feeding weevil was released, with a 95 percent destruction rate.



Young trees: These can be eradicated by cutting with secateurs at the base of the stem (easier than handpulling).
Mature trees: Trees are usually felled, with follow-up work required to eliminate seedlings. Frilling and ringbarking are also effective. Remove a 12 to 15cmring of bark near the base of the stem.
Burning: Seedlings can be burnt, if the area is medium to densely infested. Slash can also be burnt, but usually up to four years after being felled, to reduce the intensity of the fire.


Silky Hakea

Seedlings: These can be hand-pulled if burning is not ideal.
Mature trees: Mature trees should be felled, stacked together, and left to dry for between eight to tenmonths.
Burning: The stacks can then be burnt, to destroy the
dead material along with the seedlings that are germinating.
Biological control: Insects have been released which eat the seeds, thus impacting on seed production but not existing stands.



Seedlings: Seedlings can be hand-pulled or cut down below ground level.
Mature trees: These should be cut as low as possible, although herbicide should not be applied.
Burning: Fire will assist in depleting the seed bank stored in the soil.
Biological control: A moth has been released to target myrtle, but has had limited impact to date.




Long-leafed Wattle

Seedlings: Hand-pull or hoe seedlings, or treat seedlings and saplingswith a foliar spray such as Garlon (particularly if the infestation is dense).
Mature trees: Large trees should be felled, with the stump treated with herbicide. Single trees or lower infestations can be targeted through frilling, with the trees treated with herbicide.
Biological control: A wasp and seed-feeding weevil targets the trees.




All: Because brambles grow in impenetrable thickets, the bestway of controlling themis through a foliar spray using glyphosate, like Mamba Round-up. Trees can also be slashed, and the regrowth sprayed. Old growth should be cut in winter, with the spring regrowth
sprayed with foliar spray.





Seedlings: Hand-pull seedlings.
Mature trees: Cut these trees at the stump and treatwith herbicide. Alternatively use ringbarking or frilling. In order for ringbarking to be effective, make a 30cm cut around the trees. Apply herbicide to the frilled stem.









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