Effect of cassava variety on the biology of Bemisia afer (Priesner & Hosny) (Hemiptera: Aleyrodidae)

Abstract

The biology of Bemisia afer (Prisner & Hosny) reared in clip cages on leaves of 15 varieties of cassava, Manihotesculenta (Crantz)(Euphorbiaceae) was studied under field conditions during the cold months of June—August and during the warm months of September—October. Both variety and time of the year significantly affected the developmental period, the rate of population increase and the mortality. The longest mean developmental period (59.5 days) occurred on the MH108 leaves during the cold months (at 20°C and 62.9% r.h.), while the shortest (27.1 days) was on the Kithekere variety during the warm months (at 25°C and 53% r.h.). The pest population increased most rapidly on MH84 (at 5.4 eggs per female per day) and slowest on the Nigerian 3057/1 (at 0.9 eggs per female per day). The mortality of the pest indicated that Chitembwere had the greatest killing power (K = 2.555) and Nigerian 3057/1 had the least (K = 0.0760). The combined use of the developmental periods, rate of population Increase and mortality indicated that Gomani was the most resistant while Kithekere was the least resistant variety to B. afer. Other varieties with high resistance properties included MH108, Chitembwere and Mbundumali. Of the three biological characteristics used, the developmental period was the most powerful while the rate of population increase was the least. Pubescence of a cassava variety was only weakly associated with resistance to B. afer (r = 0.48) suggesting that other factors are more responsible for resistance to this pest than hairiness.