For the experiments, 20 plantlets of the wild parent M. fl abellifolia and progenies of the interspecifi c hybrid of M. esculenta (MCol 2215) and M. fl abellifolia (437-7), the source of resistance to A. socialis, were multiplied in vitro. An equal number of plants were cultivated for the BC2 families (CW67-160, CW67-130, CW67-44); MTAI-8 (BC1) and progenies of the CMB9A-9B family. The controls were MEcu-72, a source of resistance to A. socialis, and CMC40, a highly susceptible genotype of M. esculenta (Holguín et al. 2006). The plantlets, provided by the Tissue Culture Lab of the Cassava Genetics Program at CIAT, Colombia, were placed in plastic bags (250-g capacity) with sterile soil and sand (1:1) and then put in the greenhouse for 30 d (CIAT 2003). The A. socialis adults used in the trials were from the colony established at CIAT, Colombia, in 1992. All the experiments were conducted under glasshouse conditions: average 25C (range 20-30C) and 70% RH (range 60-90%).