CMD is caused by viruses of the genus Begomivirus
in the family Geminiviridae transmitted by Bemisia
tabaci, the whitefly, and disseminated in the stem
cuttings used routinely for propagation (Pita et al.
2001; Thottappilly et al. 2006). It is the most important
disease of cassava and is associated with national or
regional epidemics flaring up every few decades.
Epidemics are particularly ravaging, with root losses
as high as 100 % (Jennings 1994; Thresh et al. 1997).
Even in the absence of a serious outbreak, yield losses
of 20–90 % are common in farmers’ fields (Muimba-
Kankolongo and Phuti 1987; Moses 2008). Estimated
total crop yield losses due to CMD on the continent
amounts to about US $440 million annually (Thresh
et al. 1997). The virus has the potential to infect many
cultivars, although disease susceptibility varies greatly
(Fauquet and Fargette 1990).