The deeper cankers affect plant-conducting tissues, leading to poor plant vigour, severe wilting, and defoliation (Fokunang et al., 1999a; Van derBruggen & Maraite, 1987). These cankers serve as entry points for other pathogens such as Agrobacterium manihotis, which causes crown gall disease in South America, as well as stem, root and tuber-rotting organisms such as Sphaerostilbe repens and Armillaria mellea (Lozano & Booth,1974; Akinyele & Ikotun, 1989).