COMPARATIVE EPIDEMIOLOGY OF 3 TROPICAL WHITEFLY-TRANSMITTED GEMINIVIRUSES

Spatial and temporal patterns of spread of African cassava mosaic, okr a leaf curl and tobacco leaf curl viruses in West Africa, East Africa and India share some general characteristics. By comparing the results and running new analyses on available data, it is shown that the epid emiology of these viruses is controlled by the same key variables. For instance, spatial spread is characterised by strong border effects du e to accumulation of whitefly vectors (Bemisia tabaci) on the wind-exp osed field borders under the influence of the prevailing wind. This re sults in pronounced environmental gradients of disease. Temporal patte rns of virus spread are driven by the sinusoidal fluctuation of temper ature over the year which correspond with changes of whitefly populati ons.