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Accueil du site → Doctorat → Allemagne → Ecology and pest status of Mussidia nigrivenella Ragonot (Lepidoptera : Pyralidae), a cob borer of maize in West Africa

Universität Hannover (1999)

Ecology and pest status of Mussidia nigrivenella Ragonot (Lepidoptera : Pyralidae), a cob borer of maize in West Africa

Sétamou, Mamoudou

Titre : Ecology and pest status of Mussidia nigrivenella Ragonot (Lepidoptera : Pyralidae), a cob borer of maize in West Africa

Auteur : Setamou, Mamoudou

Université de soutenance : Universität Hannover

Grade : Doktors der Gartenbauwissenschaften (Dr. rer. hort.) 1999

Résumé
Investigations on the ecology of and control options for the maize cob borer, Mussidia nigrivenella Ragonot (Lepidoptera : Pyralidae), were conducted in the different agroecological zones of the Republic of Benin, West Africa. Country-wide surveys in maize fields and on-station experiments revealed that the borer is the most abundant and the most damaging pest of pre-harvest maize. The damage of M. nigrivenella also continues during the first two months of the storage period. A simple mathematical model, relating M. nigrivenella cob infestation levels at harvest and maize yield losses due to the borer was developed. Yield losses caused by M. nigrivenella in the field could be determined by calculating the percentage of cobs infested by the borer. Infestation of maize cobs by M. nigrivenella was also associated with Aspergillus flavus infection and subsequent aflatoxin production in maize grains. The incidence of the borer varied with the agro-ecological zones. The borer is particularly damaging in the Guinea Savannas of central and northern Benin. The evaluation of the host plant range revealed the polyphagous feeding behaviour of M. nigrivenella. Moreover, the high abundance of M. nigrivenella in the Guinea Savannas was most likely due to the overlapping fruiting periods of host plants in these zones. Life table studies of M. nigrivenella on natural host plant materials demonstrated the preference of the borer for jackbeans, Canavalia enseiformis (L.) DC. (Fabaceae). In order to avoid that this new cover crop in West Africa constitutes a potential source of infestation of M. nigrivenella for neighbouring maize fields, planting of jackbeans should be timed in such way that its fruiting period does not precede that of maize. Larvae of M. nigrivenella showed an aggregated distribution on fruits of most wild and cultivated host plant species, except for Gardenia spp. (Rubiaceae). Spatial distribution on a particular host plant species was highly correlated to the respective fruit sizes. Sample sizes and time expenditures needed to estimate M. nigrivenella populations at a precision level of 25% on the various host plants were determined. The flight activity of M. nigrivenella moths was affected both by weather factors and availability of fruits of major host plant species. Delaying the harvest of maize increased the incidence of the borer. Sun-drying of cobs at harvest for a week, however, reduced further damage in store. Investigations on the natural enemies revealed only few parasitoid species attacking M. nigrivenella and their presence was associated with the different wild host plant species. No natural enemies could be collected from maize and other crops. Parasitoids were found only on wild host plant species with the pupal parasitoid, Antrocephalus crassipes Masi (Hymenoptera : Chalcididae) being the most abundant species. Levels of parasitism were rather low. In future, biological control of M. nigrivenella should therefore pursue the ‘novel-association’ or the re-distribution approach of natural enemies, since highly efficient parasitoids of M. nigrivenella were found e.g., in Cameroon.

Mots clés : Benin ; Körnermais ; Mussidia nigrivenella ; Wirtspflanzen ; Biologische Schädlingsbekämpfung

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Page publiée le 11 juin 2008, mise à jour le 9 janvier 2019