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Invasive weeds, Africa

August 2004. Quarantine officers, Ibadan, Nigeria, asked for information and advice to sensitise scientists on the danger from inadvertent introductions of weeds from other areas. They asked for examples of weeds which have been introduced to new areas, the economic implication concerning their control and their interference with traditional farming.

The members were referred to a number of useful text:

A Global Compendium of Weeds or visit the website that contains a very early draft of this compendium at The book lists origins, weed status and references for each species. As a resource to determine potential threats it contains a wealth of data that would help you build a case such as you require.

The publishers can be contacted online also at: For more on the book see:

It was also suggested that the questions be put to the Alians List, which is which is operated by the Invasive Species Specialist Group (ISSG) of the IUCN, based in New Zealand. The International Phytosanitary Portal (Internationa Plant Protection Convention)

The invasion of Opunita in parts of Africa was suggested as a good example of the damage that alien weeds can do.

Opuntia ficus-indica is very invasive in arid regions of Ethiopia. This species was brought to Ethiopia by the Italians during the colonial period (1930s) as a culinary plant, for the fruit. It has become very extensive in many areas, primarily because it appears to have no local pests and is very vigorous, so much so that harvesting fruit is very difficult as the plants grow so high, and some areas are almost impenetrable. It illustrates the problems of the introduction of plants initially for what appear to be beneficial reasons that turn out to be mistakes.

The Opuntia story in Ethiopia, is illustrated at:
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