BIOLOGY AND HARMFULNESS OF INVASIVE DISCOSCOREA IN SUGARCANE (SACHARUM OFFICINARUM L.) CULVITATION IN THE AREA OF THE SUGAR REFINERY COMPLEX OF FERKESEDOUGOU IN NORTH COTE D’IVOIRE

*Author for Correspondence Floristic sampling done in hundred plots around the sugar refinery complex of Ferke 1 and Ferke 2 located in Ferkessedougou in North Cote d’Ivoire during the cropping cycle of 2011-2012, revealed 30 species of weed including 6 of invasive Discoreas as D. bulbifera, D. dumetorum, D. hirtiflora, D. lecardi,. paraehensillis and D. preussii. Observations done on the biology, the phenology and the harmfulness showed that the occurrence of invasive Dioscorea in sugarcane fields was effective by bulbils and in certain level by tubers and bulbils generating new tubers, when produced during the vegetative growth stage between the second and seventh months of cultivation. D. bulbifera, D. dumetorum, D. hirtiflora and D. lecardi were producer of bulbils and occurred in highest potential densities. Excepted for D. lecardi, they were more harmful to sugarcane plant because of overlapping of vegetative cycle durations likewise for D. praehensilis. Hence, these weeds may have high competiveness ability with the crop for soil water and nutrient uptake as well as for sun light reception. Key Words: Weed, Dioscorea, Sugarcane, Biology, Phenology and Harmfulnes