Combating alien invasive plant species

In the fight against invasive alien plant species, the Working for Water programme has used various methods:

Mechanical methods – felling, removing or burning invading alien plants.

Chemical methods – using environmentally safe herbicides.

Biological control – using species-specific insects and diseases from the alien plant’s country of origin. To date 76 biocontrol agents have been released in South Africa against 40 weed species.

Integrated control – combinations of the three approaches above. An integrated approach is oſten required to prevent high environmental impacts.2

Despite the widespread distribution and extent of alien invasive species in South Africa, actions to control invasive alien plants can have major results. A good example is infestation by wa- ter lettuce (Pistia stratiotes) originating in South America. Te picture shows how water lettuce was combated in 1998 using

biological control, and the major effects this initiative had on the alien plant within a timeframe of only a few months.3

May 1998 October 1998

Water lettuce before and after biocontrol, 1998.

(Photo: C. Cilliers)

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