Cassava Mosaic Disease Transmission by Whiteflies (Bemisia tabaci Genn.) and its Development on Some Plots of Cassava (Manihot esculenta Crantz) Clones Planted at Different Dates in Togo

A study was carried out to determine the effect of planting date on Cassava Mosaic Disease (CMD) transmission by white flies (Bemisia tabaci) and its development in a population of cassava clones selected at Lomé Agricultural Experimental Station (LAES) of the High School of Agriculture, University of Lomé in order to contribute in the search of a strategy of effective control of CMD in Togo. To achieve this goal, cassava clones resulting from seeds of the third generation (F3) were planted at different dates on plots P1, P2 and P3 with the interval of 21 days. Three weeks after the establishment of the planted seedlings, data assessment was initiated weekly during twenty weeks. And the measured parameters were: (i) weekly counting of whitefly population on seedlings per plot of 114 m2 and (ii) weekly visual observation to quantify the diseased seedlings according to an assessing note on the severity of the disease ranging from 1 to 5. The results obtained from the visual observations made during this study, revealed that the propagation of the disease on each plot of the evaluated clones is proportional to the size of the population of vectors in presence. Thus, three months after plantation, it was numbered 53% diseased individuals (p<0.05) among the population of cassava clones; at the same time, the population of whiteflies reached an average 1.49±5.23 to 7.83±12.81 individuals by cassava seedlings under the conditions of this work. It was observed that the most significant number of whiteflies was noted on the plots P2 and P3. It was noticed that the plot P3 which was installed six weeks after plot P1, 41% of the seedlings died (p<0.05) due to the infestations of eggs and the larvae of whiteflies.