Multiple parasitism by Cotesia sesamiae and Cotesia flavipes (Hymenoptera : Braconidae) on Busseola fusca (Lepidoptera : Noctuidae)

Busseola fusca (Fuller) is one of the most important pest of cereals in sub -Saharan Africa. Cotesia sesamiae (Cameron) is the predominant parasitoid a ttacking B. fusca larvae in many pm ts of Africa. An exotic parasitoid, Cot esia flavipes Cameron, was introduced into Kenya in 1993 for the control of Chile partellus (Swinhoe). Laboratory studies indicated that although C. f lavipes would search for; and attack B. fusca, it was not able to complete its development in this host. The aim of the present study was to investiga te the outcome of multiple parasitism of B. fusca by the two Cotesia specie s. The study showed that when both parasitoid species stung a B. fusca lar vn at the same time, both parasitoids emerged from more than half of the ho st larvae, C. flavipes alone emerged from 17%, and C. sesamiae alone emerge d from 9%. When the larvae were parasitized by C. sesamiae first, and then 2 h later by C. flavipes, and vice vel sa, most of the progeny were C. flav ipes. However; when B. fusca larvae were string by C. sesamiae three days b efore oviposition by C. flavipes, significantly more C. sesamiae emerged fr om the larvae. When C. flavipes oviposited first, no larvae produced C. fla vipes only. The interaction of parasitoids and the host immune system, and the implications of these results for the biological control of stem borers in East Africa are discussed.