Busseola fusca Fuller is one of the major lepidopteran stemborers of maize and sorghum in Africa. Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) is an indigenous, gregarious larval endoparasitoid that attacks mid- to late-instar stemborer larvae, which is reported to be one of the most important larval parasitoids of B. fusca in many countries in sub-Saharan Africa. Previous work has shown that two biotypes of C. sesamiae occur in Kenya which express differential abilities to develop in B. fusca. A biotype from western Kenya successfully develops in B. fusca, while a biotype from the eastern coastal area does not. We treated fourth-instars of B. fusca with calyx fluid from C. sesamiae from western Kenya (Kitale) before offering them to C. sesamiae from the Coast (Mombasa) for oviposition, and found that the eggs were not encapsulated. This suggests that factors in the calyx fluid of C. sesamiae from the western Kenya biotype were responsible for suppressing the immune system of B. fusca. We speculate that polydnaviruses in the calyx fluid were involved in disarming the host immune system, and that the polydnaviruses in the two biotypes are genetically different.

A study was undertaken to test the hypothesis that the quality of host plant parts determines the nutritional quality of herbivorous insects feeding on it to their parasitoids. A Gossypium hirsutum-Helicoverpa armigera-Campoletis chlorideae tritrophic system was evaluated. The superior nutritional quality of bolls and young leaves of Gossypium hirsutum (MCU-5 variety) contributes to more efficient feeding, growth and reproduction of the bollworm, Helicoverpa armigera (Hübner) and better survival of its larval parasitoid, Campoletis chlorideae Uchida. Longer total developmental duration and decrease in adult longevity were observed in H. armigera reared on senescent leaves than in those reared on bolls. Consumption, growth rate and efficiency measures were significantly lower in parasitised H. armigera larvae than in unparasitised larvae. Percentage parasitism was highest (84.1%) in H. armigera fed on bolls. The parasitoid C. chlorideae displayed shorter developmental duration and improved survival on H. armigera fed on bolls.

This paper reviews the work which had been done in Nigeria from 1911 to 1981 on several aspects of the biology of Zonocerus variegatus (L.), a variegated grasshopper pest of many food crops. The account covers recent advances in the areas of breeding biology, locomotory and migratory activities, morphometrics, feeding habits, parasitisation, and strategies for effective control of the grasshopper in Nigeria.