C.A. Omongo, J. Colvin, G.W. Otim-Nape, J.M. Thresh and R.J. Cooter
A severe epidemic of cassava mosaic disease (CMD) has been traversing Uganda from north to south devastating cassava fields and causing food shortages since 1988. Studies were undertaken to better understand the spread of the disease in relation to its whitefly vector by serial plantings of CMD-free cassava var. Bao at eight sites spaced 7-9 km intervals along a N-S transect in southern Mukono district each season from June 1996 to October 1997. CMD incidence increased systematically southwards over the period. Cumulative disease incidences at seven month after planting for example were 4.6% in May 1997, 6.9% in September 1997, 27.1 % in January 1998 and 97.8% in June 1998 at Katosi which was the southernmost location. Corresponding changes in whitefly populations were recorded. Implications of results for the control of CMD are discussed.