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Accueil du site → Master → Kenya → 2005 → Studies on species diversity, host preference, host suitability, longevity and fecundity of native egg parasitoids of stemborers in semi-arid Kenya

Kenyatta University (2005)

Studies on species diversity, host preference, host suitability, longevity and fecundity of native egg parasitoids of stemborers in semi-arid Kenya

Okoth, Evans Ouma

Titre : Studies on species diversity, host preference, host suitability, longevity and fecundity of native egg parasitoids of stemborers in semi-arid Kenya

Auteur : Okoth, Evans Ouma

Université de soutenance : Kenyatta University

Grade : Master of Science MSc 2005

Résumé
Infestation and damage by lepidopteran stemborers is one of the major causes of low maize yields in Kenya. Among the biological management options of stemborers, egg parasitoids are some of the potential agents that can be included in the integrated management strategy for the pests. Information on the species diversity and the role of egg parasitoids in stemborer control is lacking in the semi-arid eastern and central regions of Kenya. The aim of this study was to determine the egg parasitoid species diversity and to assess their contribution in enhancing lepidopteran stemborer eggs’ mortality in semi-arid eastern and central regions of Kenya. This was first investigated through field surveys by collecting stemborer eggs from farmers’ maize fields in Kitui and Thika distrcits. No egg batches were recovered from the plants in Kitui in Eastern province and Thika in Central province during the long rains, of 2003 unlike the short rains, 2003, where 9 egg batches of Chilo partellus and 19 batches of Sesamia calamistis were recovered from Thika district. Five out of the 19 egg batches of S. calamistis yielded Telenomus busseolae (Gahan). On-station studies were also conducted where maize plants were artificially infested with Chilo partellus and Sesamia calamistis eggs in order to determine egg parasitism in the eastern region. Egg parasitism ranged from 0.34-12.54% in both Katumani and Kiboko. However, Kiboko had significantly higher parasitism levels than Katumani during both the long (t = 5.04 ; df = 2209 ; p <0.0001) and short rainy seasons of 2003 (t = 11.73 ; df = 2021 ; p < 0.0001). The parasitoid species recovered from the stemborer’ eggs in Kiboko were T. busseolae, T. isis, Telenomus spp., Trichogramma spp. and Trichogrammatoidae spp., while in Katumani, it was Trichogramma spp. The abundance of the parasitoids in descending order was T. busseolae, T. isis (Polaszek), Trichogramma spp., Telenomus spp., and Trichogrammotoidae (58.9, 17.81, 13.01, 9.59 and 0.68% respectively) at Kiboko.

Mots clés : Stem borers — Kenya//Parasitoids — Kenya//Lepidoptera—Kenya

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