Cotesia flavipes Cameron (Hymenoptera: Braconidae), a gregarious larval endoparasitoid of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) and other stemborers in the Indo-Australian region, was released in Mozambique for the first time in 1996. Before its release, countrywide surveys on stemborers and their natural enemies were conducted in several places. However, all led to the same conclusion: that Ch. partellus was the most abundant stemborer at the majority of locations, and that the rate of larval parasitism was very low (< 5 %). To evaluate the effect of stemborer species composition on the establishment of Co. flavipes, two releases were made at two agroecologically different sites during the 1998/1999 and 1999/2000 growing seasons. Cotesia flavipes was recovered from all the three stemborer species found at each site during the season of release and a year later. However, the rates of parasitism were very low, ranging from 0.6 to 1.9 % on Ch. partellus, 3.2 % on Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and 2.6 % on Busseola fusca Fuller (Lepidoptera: Noctuidae). The native natural enemy, Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) was the most common larval parasitoid at the two sites. The recoveries of Co. flavipes during the release period and a year later indicate that this exotic parasitoid has become established at the two locations in the southern and central regipns of Mozambique, in spite of differences in stemborer species composition. However, it is too early to evaluate the impact of Co. flavipes on the stemborer populations.

The palaeotropical, gregarious, endoparasitic braconids Cotesia sesamiae, Cotesia flavipes and Cotesia chilonis were recently imported into Benin as candidates for biological control of stem and cob borers of maize. Host acceptability and host suitability of six gramineous borers occurring in western Africa, namely the noctuids Sesamia calamistis, Sesamia poephaga, Busseola fusca and the pyralids Coniesta ignefusalis, Eldana saccharina andMussidia nigrivenella, to these candidate parasitoids was evaluated in order to gain insight into the physiological suitability of the natural and factitious hosts. All hosts were accepted by all Cotesia spp., except M. nigrivenella which was not attacked by Co. chilonis. Parasitoid progeny development was successful in S. calamistis, S. poephaga and Con. ignefusalis. Sesamia calamistis was the most suitable host for Cotesia spp. development, in terms of duration of developmental time, brood size and mortality of parasitoid progeny.