Why Callosobruchus rhodesianus causes limited damage during storage of cowpea seeds in a tropical humid zone in Togo |
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Authors: | Komina Amevoin Isabelle Adolé Glitho Jean Paul Monge & Jacques Huignard |
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Institution: | Laboratoire d'Entomologie Appliquée, Facultédes Sciences, Universitéde Lomé, BP 1515, Lomé, Togo;;Institut de Recherche sur la Biologie de l'Insecte, UMR CNRS 6035, Universitéde Tours, Avenue Monge, Parc Grandmont, 37200 Tours, France |
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Abstract: | The sympatric bruchids Callosobruchus rhodesianus (Pic) and Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) colonize cultures of cowpea, Vigna unguiculata (Walp.) (Papilionaceae), in Togo at the end of the rainy season. Seeds containing larvae of the two bruchid species were introduced into the storage systems. Callosobruchus rhodesianus adults emerged from the seeds at the beginning of storage, but this species disappeared quickly and C. maculatus became dominant. Analysis of the reproduction of females collected at the beginning of storage made it possible to distinguish between four groups of females differing in their reproductive activity. Three groups were sexually active but they differed in their fecundity and the duration of the latency period before the first oviposition phase. The fourth group of females was in reproductive diapause. In interspecific competition, the presence of C. maculatus larvae reduced the survival chances of C. rhodesianus and therefore is disadvantageous for this species. The main factors explaining the rapid decrease of the C. rhodesianus populations under storage conditions were the variability of female reproductive activity with the emergence of insects in reproductive diapause and the significant larval mortality in interspecific competition with C. maculatus. |
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Keywords: | Coleoptera Bruchidae female reproductive variability larval interspecific competition reproductive diapause seed storage conditions Callosobruchus maculatus |
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