Cogongrass is a serious weed in small-scale farms in the lowland humid zone of West Africa. This study evaluated the response of cogongrass to herbicides and the legume cover crop velvetbean in cassava and white Guinea yam. In 2001/2002, cassava tuber yields and gross returns in treatments that received glyphosate alone were higher than in plots that received fluazifop-P-butyl once. In 2002/2003, treatments that received fluazifop-P-butyl once, glyphosate alone, glyphosate integrated with sowing velvetbean, or hoeing only, had higher cassava tuber yields than other treatments. Gross returns were higher in treatments that received glyphosate followed by sowing velvetbean or those hoed only than in other treatments. Fluazifop-P-butyl applied twice, glyphosate alone, or glyphosate followed by sowing velvetbean reduced cogongrass shoot biomass more than other treatments. Rhizome biomass was lower in plots that received glyphosate alone than in all fluazifop-P-butyl treatments. In 2002, white Guinea yam tuber yields were highest in plots that received glyphosate alone and lowest in plots where fluazifop-P-butyl was applied alone or followed by sowing velvetbean. The highest gross return was obtained in plots that received glyphosate alone while the lowest was obtained in plots that received fluazifop-P-butyl once followed by sowing velvetbean. In 2003, the highest tuber yields and gross returns were from plots that received glyphosate alone, fluazifop-P-butyl alone, or those hoed only. The hoed-only plots had 14 times higher cogongrass shoot biomass and 7 times higher rhizome biomass than other treatments. In both crops, hoeing alone or followed by sowing velvetbean was more costly than chemical control. The highest margin over hoeing was obtained from plots that received glyphosate alone. Sensitivity analysis showed that using glyphosate was more cost effective than fluazifop-P-butyl, even if the cost of the herbicide increased by 100% or the cost of labor decreased by 30%.

Speargrass severely constraints crop production in the sub-humid lowlands of West Africa. Researchers have identified and demonstrated effective management techniques but the adoption rate among farmers is still low. Data were collected from 41 communities in Cross River, Kogi and Benue States in Nigeria using rural rapid appraisal techniques. The objectives were to assess the importance of agriculture in the livelihoods of each community, identify priority crops, assess perceptions of the speargrass problem, identify existing speargrass control strategies and local institutions/farmers with the capacity to implement speargrass control trials. Crop production was the main source of livelihood for all households. The most important crops from the perspectives of both food security and cash sale were cassava and yam, and these were most affected by the weed. Speargrass was the major constraint to crop production because of lack of capital for hiring labour and purchasing inputs, declining soil fertility, bush burning, deforestation, continuous cropping and lack of required skills. Slashing, hand-pulling, burning, deep digging and fallowing were the most common control methods used by farmers, but these were very labour intensive and ultimately not effective. Farmers assessed speargrass control measures through labour and cash requirements, material availability, effectiveness, time span to achieve control and crop yields. They rated chemical control most highly. Longer fallow periods and re-afforestation were effective but impractical as pressure on land intensifies from population growth. From the results of this study, we conclude that the use of community-based participatory approaches is essential to identify various technologies for combating speargrass.

One of the most invasive weeds in sub-humid Savannahs of West Africa is Imperata cylindrica. Increasing spread threatens the sustainability of the natural resource base and rural livelihoods. Although farmers achieve some control through hand weeding, fallow, burning and limited use of chemicals, Imperata remains a serious problem. A participatory approach involved stakeholders in problem diagnosis, action planning, with farmer-led monitoring and evaluation of control methods. Major determinants for farmer choice of control technique were identified as cost, labour requirement, effectiveness, input availability, yield increases, knowledge and long-term sustainability. Farmers ranked herbicide as the most effective method of controlling Imperata particularly in maize, cassava and soya-bean, second was a combination of Mucuna and herbicide, third Mucuna and hand-weeding and fourth hand-weeding only with noticeable gender and age differences between farmers. Although herbicides increase cash needs, they reduce labour requirement, contribute to higher income, food security, and sustainability. Action is now taking place to scale up results of this approach through expanding extension, NGO, private sector and farmer involvement in problem diagnosis, farmer-led evaluation, improving input availability, providing access to credit and increasing farmer knowledge of chemical use. Improving public/private partnerships is seen as key to achieving this goal.