“Alien invasive” plants rapidly colonise undisturbed, pristine areas, displacing indigenous vegetation and transforming the plant community. Removing alien plants is important to keep the ecology of your property healthy. Alien plants are one of the most important causes of plant extinction worldwide. Many use a great deal of water, while others change the composition of the soil. Thorny or spiny invaders sometimes create impenetrable barriers that prevent access to streams, pastures and shade trees. Some alien plants are toxic to humans, while others are toxic to animals.
Eradication methods should be used that are appropriate for the species concerned as well as to the ecosystem in which they occur.
Methods of Removal
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.
Sometimes a combination of methods is the best solution.
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.
Main image: Famine weed. Image courtesy ARC