The influence of NPK fertiliser on the symptoms and spread of cassava mosaic virus disease (CMD) and on populations of the whitefly vector ( Bemisia tabaci
) was investigated in Uganda using three cassava varieties: Migyera (CMD-resistant), Nase 2 (tolerant) and Ebwanatereka (highly susceptible) in 1995-96 and 1996-97 planting seasons. In each season NPK fertiliser significantly (P<0.05) increased the incidence of CMD and led to earlier infection and spread of the disease for varieties Migyera and Nase 2 than in unfertilised control plots, whereas for variety Ebwanatereka no significant differences in infection and disease spread were observed for the control and plots that received NPK application. Adult whitefly populations per shoot were increased significantly (P<0.05) by NPK fertiliser on Nase 2 and Ebwanatereka in 1995-96 and on Ebwanatereka in 1996-97, although the increases were not significantly different. Application of NPK fertiliser did not significantly influence the population of whiteflies on variety Migyera in either experiment. Similarly, NPK fertiliser application did not influence CMD symptom severity for all varieties in either season. These results indicate that NPK fertiliser application is not satisfactory strategy for facilitating the control of CMD.