War of the weeds
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CTA. 2002. War of the weeds. Spore 98. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/46485
Internet URL: http://spore.cta.int/images/stories/pdf/old/spore98.pdf
In eastern Africa, farmers plant napier grass (Pennisetum purpureum) or Sudan grass (Sorghum vulgare sudanese) as a trap weed in maize. The stem borer, accountable for up to 30% yield losses in maize, prefers these grasses to maize. Two other weeds...
In eastern Africa, farmers plant napier grass (Pennisetum purpureum) or Sudan grass (Sorghum vulgare sudanese) as a trap weed in maize. The stem borer, accountable for up to 30% yield losses in maize, prefers these grasses to maize. Two other weeds are planted that repel stemborers: molasses grass (Melinis minutifolia) or the silver-leafed desmodium (Desmodium uncinatum). The trick is to plant repellent weeds in the maize field to chase out the stemborers, and to plant the trap weed on the edges of the field. The stemborers are caught in the sticky substance that these trap weeds produce. Both napier and Sudan grass are also used as fodder. Molasses grass not only repels stemborers but also ticks. Nonetheless, desmodium seems to excel its colleagues in usefulness. It fixes nitrogen in the soil, is an important source of fodder, repels stemborers and most surprisingly: it turns out to repel the noxious weed striga too (see other box). During trials, as much as 40 times less striga was found in the desmodium maize fields, compared to mono-cropped maize. The International Centre for Insect Physiology and Ecology, based in Nairobi, developed, tested and disseminated the combined intercropping system. It has caught on extremely well. Farmers both smallholder and large commercial from Ethiopia to Tanzania are now planting desmodium in their maize. One spin-off effect of this popularity is that selling desmodium seed has become an emerging income-generating opportunity. In Togo and Benin, Mucuna spp. have been brought into action as cover crops to restore the fertility of arable land and reduce weed infestation. It has caught on especially in areas of high rural population density, where land pressure is high and periods of fallow are not long enough. Growing mucuna during the improved fallowing suppresses spear grass infestation (Imperata cylindrica) but it is also grown intercropped with maize. The technique is spreading fast and mucuna seed sales are a booming business.