Striga is a parasitical weed attacking cereals and cowpea (see picture). There are two species (types) of striga: the striga hermonthica, which attacks millet, sorghum, maize and rainfed rice, and the striga gesneroides, which attacks cowpea and wild leguminous plants. Striga attack increases in general when soil fertility diminishes. A striga attack may have a very harmful effect on millet yield. It is difficult to control striga because striga grains may remain alive in the soil for at least 5 years.

Several methods must be combined in order to efficiently control striga (Ly et al. 1998).

1. Resistant varieties: The Sangaranga and Korobalen varieties of cowpea are resistant to striga. Such resistance is absolute. For millet, it is difficult to develop resistant varieties. In sorghum, tolerant varieties have been developed.
2. Three weedings are required in order to control striga development. The third weeding must occur late in the season in order to avoid that striga produces grains.
3. A mineral fertiliser or manure input may contribute to reducing striga attacks because fertilization makes plants stronger. Microfertilising also reduces striga attacks. 
4. The intercropping of cereals with crops such as cowpea, which is resistant, and groundnuts, which are not attacked, can considerably reduce striga attack. 
5. Late planting can also reduce striga attack if this method is combined with weeding.

For more information on striga:

FAO document: http://www.fao.org/ag/AGP/AGPP/IPM/Weeds/Issues/striga2006.htm

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