Composition of stem borer communities in selected vegetation mosaics in Kenya

Busseola fusca (Fuller), Sesamia calamistis Hampson, Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) are important stem borer pests of maize and sorghum in East Africa. Persistence of these pests in crop fields is blamed on the influx of diaspore populations from the neighbouring natural habitats. In addition to pest species, natural habitats support numerous non-economic stem borer species, some not known to science. However, due to growing human populations and accompanying global change, some of the natural habitats are undergoing rapid changes, a process that may result in the evolution of “new” pest species. In this study, we investigated stem borer species diversity in four different vegetation mosaics in Kenya, with an aim of establishing the differences in species composition and distributions in both wild and cultivated habitats. We identified 33 stem borer species belonging to 14 different genera in the four families; Noctuidae, Crambidae, Pyralidae and Tortricidae from 37 plant species. In addition to the above stem borer pest species, we found three more species, Busseola segeta Bowden, Pirateolea piscator Fletcher and Eldana saccharina Walker, in the cultivated fields. Together, stem borer pests varied in distribution among vegetation mosaics, suggesting differences in ecological requirement. Despite the variations in distribution patterns, stem borer pests co-existed with non-economic species in the natural habitats, communities that are facing threats due to ongoing habitat changes. This paper discusses the likely impacts of habitat changes on both pest and non-economic species.