Abstract: Aphis spiraecola (Patch), a ubiquitous aphid in West Africa has been implicated in the transmission of most potyviruses reported from Nigeria. The transmission efficiency of two Nigerian strains of MWMV designated as MWMV-lag and MWMV-cor in this study, by two clones of the aphid was studied. The transmission efficiency was determined based on aphid number per plant, varying Acquisition Access Periods (AAPs) and varying post-acquisition starvation times. Both clones of A. spiraecola were found to be efficient vectors of the two MWMV strains causing 100% transmission rate with as few as 5 individual aphids. The result of this study indicates that transmission efficiencies of MWMV-cor and MWMV-lag strains by the Aphis spiraecola clones declined with prolongation of AAPs. Clone I was more efficient in transmitting MWMV-cor than MWMV-lag. For clone II, both virus strains were transmitted with equal efficiency differing by 6.7% where differences occurred. Both clones transmitted MWMV-lag more efficiently that it did MWMV-cor with respect to the sequestration time regimes employed. Percentage differences ranged from 6.6-40% for MWMV-cor and 11.3-30% for MWMV-lag. On clonal basis, clone I did better in retaining and transmitting MWMV-cor that did clone II while MWMV-lag was retained much longer than MWMV-cor by clone II.