Species diversity and abundance of lepidopteran stem borer natural enemies in Botswana

Abstract

Africa hosts significant lepidopteran stem-borers which are attacked by a diversity of natural enemies in their natural and cultivated environments. To determine diversity, relative abundance of stem-borer natural enemies and associated host plants, field surveys were conducted during 2014/15 and 2015/16 austral summer on natural and cultivated habitats across Botswana. In cultivated habitats, the common larval parasitoids recorded were Cotesia flavipes, and C. sesamiae, and pupal parasitoids Pediobius furvus and Gambroides nimbipennis while in natural habitats, larval parasitoids Chelonus curvimaculatus and Goniozus indicus and a pupal parasitoid, Dentichasmias busseolae were recorded. Furthermore, predatory ants (Linepithema humile, Crematogaster peringueyi and Aenictus species) were recorded in both cultivated and natural habitats. Cultivated and natural Poaceae; maize, sorghum, sweet sorghum, Echinochloa pyramidalis; natural Typhaceae, Typha latifolia and natural Cyperaceae-Schoenoplectus corymbosus and Cyperus dives formed the major plants hosting stemborers and related natural enemies. Chilo partellus and Sesamia spp. were the major parasitoid hosts with C. partellus predominating in cultivated habitats and Sesamia jansei in natural habitats. Larval parasitism ranged from 2.1-34.7% and 3.3-14.3% while pupal parasitism ranged from 6.1- 10.6% and 6.7-9.1% in cultivated and natural habitats respectively. Parasitoids relative abundance ranged from 1.1-41.6% and 4.8-38.1% in cultivated and natural habitats respectively, with C. flavipes dominating in cultivated and C. curvimaculatus in natural. Overall, our results show that cultivated and natural environments in Botswana harbour parasitoid faunal diversity that may be worth conserving for future efficacy of biological control programmes, and an equally diverse flora hosting these stem-borers.