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Surveys were completed in Eritrea, Ethiopia, Kenya, Madagascar, Mozambique, Tanzania, Uganda and Zanzibar to assess the lepidopteran stem borer species diversity on wild host plants. A total of 24,674 larvae belonging to 135 species were collected from 75 species of wild host plants belonging to the Poaceae, Cyperaceae and Typhaceae. Amongst them were 44 noctuid species belonging to at least nine genera, 33 crambids, 15 pyralids, 16 Pyraloidea species not yet identified, 25 tortricids and three cossids. The noctuid larvae represented 73.6% of the total number of larvae collected, with 66.3, 3.5 and 3.8% found on Poaceae, Cyperaceae and Typhaceae, respectively. The Crambidae, Pyralidae, Tortricidae and Cossidae represented 19.8, 1.9, 2.5 and 0.1% of the total larvae collected, respectively, with 90.4% of the Crambidae and Pyralidae collected from Poaceae, and 99.7% of the Tortricidae collected from Cyperaceae. The lepidopteran stem borer species diversity in the wild host plants was far more diverse than previously reported.

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The effects of mixed cropping systems containing maize, sorghum, millet and beans on infestations of cereals by lepidopteran stemborers and on associated parasitoids, as well as on yields and land equivalent ratios (LER) were assessed during four consecutive rainy seasons at two sites in the semi-arid eastern region of Kenya. Systems containing the non-host bean were more efficient in reducing pest densities than those with millet or sorghum only. Higher parasitism in diversified systems compared to monocrops was due to density-dependent effects rather than superior suitability of such systems to parasitoids. The maize-bean system, which had the highest proportion of bean plants, had LERs >1.65 while most other systems had LERs <1. It is concluded that mixed cropping with several cereal species has little advantages in terms of yield loss abatement due to stemborers and land use efficiency. However, including the drought-tolerant crops such as sorghum and millet in the system stabilizes food security in drought-prone areas such as eastern Kenya.

Cotesia flavipes Cameron has been released several times in Africa for biological control of gramineous stem borers. Establishment has been reported on the Indian Ocean islands of Mauritius, Reunion and Madagascar, however, several attempts to introduce C. flavipes into continental Africa are reported to have failed. Recently, several cocoon masses of C. flavipes were recovered from south-western Kenya where the parasitoid was never released. Identifications of the parasitoids from south-western Kenya were based on morphological characters, allozyme frequencies, and mating experiments with laboratory populations of C. flavipes. It is hypothesized that C. flavipes became established from individuals escaping from a laboratory colony maintained in south-western Kenya in 1991.

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Cotesia fl avipes Cameron (Hymenoptera: Braconidae) was fi rst imported into Kenya in 1991 from Pakistan for control of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). First releases were made at the Kenya coast in 1993 and a few recoveries of the parasitoid were made the following year. Additional foreign exploration for C. fl avipes was conducted in central India in 1996 and 1998, which resulted in additional importation of the parasitoid for subsequent releases in eastern and southern Africa. Region-wide releases commenced with releases in Mozambique in 1996