How to recognize a weed ?
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Classical methods: the constraints of the identification keys
The weeds must be identified as from their early vegetative stage. However, the classical identification methods are based on the floral structure.
On the other hand, the use of the identification keys makes it necessary to answer a large number of successive questions to finalize an identification. Since the answers are not always available being given the absence of the sample’s character, the method cannot lead to the identification of the said plant. Furthermore, the use of identification keys calls for a lot of technical terms known by a few non-botanists.
Multimedia contribution: Advenrun, identification software accessible on-line
AdvenRun is an identification and information software accessible on-line and which contains around a hundred da ta sheets on crop weeds in Réunion. That tool makes the identification of plants possible as from a plant’s profile.
This method has several advantages :
- it only uses drawings without any technical terms,
- it leaves to the user the choice of the characteristics to be described,
- it tolerates lack of information and therefore incomplete samples as well as observation errors,
- at each stage of the identification, a likeness probability is calculated for each species. Those are then sorted in decreasing order of likeness.
Each species data sheet contains a distribution map in Réunion, pictures, a botanical drawing and description as well as botanical and ecological data. The technical terms used in the texts refer to the illustrated definitions in the glossary.
The CD is accompanied by a field handbook for 50 species.
Recommended literature for the tropical zone :
In West Africa, only Flora of West Tropical Africa is complete in terms of systematic approach, but it doesn’t help to identify plants without flowers and is in English. It’s also the case for the Flora of Mauritius and the Seychelles.
Other regional or national floras are incomplete, as all plan families have not been dealt with. Others are still in preparation (Cameroon Flora, Congo Flora, …) or near publication (Flora of Tropical East Africa, Flora of Zambezi, Flora of the Mascarenes, Flora of Madagascar, Flora of Thailand, Agrostogic Flora of Madagascar...). For others, only one family is treated (Flora of the Niger Poaceae, Flora of the Ivory Coast Poaceae, Agrostological Flora of Madagascar…)
The Flora of Senegal has the advantage of having an identification key concerning first the vegetative characters, thus making it possible to identify or getting closer to the identification of non-flowering samples.
Some floras contain only one identification key, while others include a complete botanical description of each species. It’s generally the case for national floras.
Some publications concern weedsspecifically on one region or one crop.
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