Cassava

Abstract

At least one member of the whitefly Bemisia tabaci (gennadius) (Hemiptera: Aleyrodidae) species complex is a vector of cassava mosaic geminiviruses and cassava brown streak viruses, which cause serious damage to cassava, Manihot esculenta Crantz. The whiteflies are predominantly attacked by Eretmocerus mun dus Mercet and Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphe­ linidae). These parasitoids had, however, not been able to control B. tabaci populations on cassava. This study therefore aimed at elucidating how life history parameters limit the performance of the parasitoids. We conducted the study under fluctuating laboratory conditions to determine the development duration, longevity and fertility of these parasitoids. The initial egg count on emergence and development duration were higher in E. mundus than in E. sophia. similarities occurred in the development duration of females and males E. mundus , whereas the females of E. sophia developed about two days earlier than their males. Mean longevity of females when provided with honey diet was 5.4 days for E. mundus and 6.6 days for E. sophia , and averaged 5.5 days and 11.3 days, respectively, when developed on whitefly nymphs. Progeny production averaged 25.6 off­ spring for E. mundus and 16.5 for E. sophia . The net reproduction rate of E. mun dus was 13.1 as opposed to 15.5 for E. sophia . The intrinsic rate of increase was 0.10 for E. mundus and 0.11 for E. sophia . mean generation time was 24.9 and 26.2 days for E. mundus and E. sophia , respectively. The results suggest that E. mundus is the most suitable candidate for high B. tabaci population control, whereas E. sophia may be effective under low B. tabaci populations.