Eradication of Alien Vegetation

The sceptics among us might question why such a fuss is made about invasive alien plants. Perhaps we first need to define “problem plants” before we consider why they are regarded as a threat.
A weed is a plant, especially a wild plant, growing where it is not wanted. A “declared weed” in South Africa refers to plants that have been categorised in terms of regulation 15 of the Conservation of Agricultural Resources Act as Category 1 plants: they are totally prohibited and may not be planted, propagated, imported, sold or even acquired. Eradication methods should be used that are appropriate for the species concerned as well as to the ecosystem in which they occur.
There are four basic methods of removing invasive plants:
Mechanically: removing or sufficiently damaging plants by uprooting, clear-felling, slashing, mowing, ring-barking or physically hauling out the plants out.
Chemically: applying registered herbicides to the problem plants or to the soil around them, with the aim of killing or suppressing them.
Biologically: introducing host-specific natural enemies, such as insects or pathogens (e.g. fungi). The Plant Protection Research Institute is the only nominated authority for the biological control of alien invasive plants in South Africa.
Use of fire: if used under carefully controlled conditions, fire is sometimes the most effective way to ensure the complete eradication of all parts of an invader.
Indirect control: the area can be over-sown with beneficial plant species, which are supported until they are able to overcome the invading species.
The aim of control is to reach a point where, ideally, the plants concerned no longer occur in that particular area and the best results are often achieved by combining more than one form of weed control. In most cases follow up activity will be required to finally eradicate the problem plant.
Rehabilitation of the area is also vital. Often the planting of suitable grass species will be the best means of allowing the soil to build up and preventing soil erosion.

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