Insecticides and dynamics of Bemisia tabaci Gennadius populations in cotton fields of Burkina Faso

Regarded in the past as a secondary pest, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) has since the 1997-1998 cropping season become one of the most significant pests in the cotton fields of Burkina Faso. The implementation of an effecient control strategy against B. tabaci necessarily implies a better knowledge of the biology of this pest. The objective of this study is to develop a fast technique for the sampling of the larvae on the one hand and to follow the biology of B. tabaci in two sites of western Burkina Faso (Boni and Farako-Ba) on the other hand. The results obtained show that the larvae of B. tabaci are more important on the basal leaves of branches 3, 4, and 5. On each leave, lobes B and C are the zones B. tabaci larvae are most partial to. The survey of the dynamics of B. tabaci populations shows that chemical treatments seem to have no impact on the total number of B. tabaci. They may even have a favourable effect on the development of the pest. Moreover, the damage observed is slight and no difference is found between treated and untreated fields. The overall results of this study provide some information as to the biology of B. tabaci and should pave the way for the development of an efficient integrated control strategy against this pest in Burkina Faso.