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The potential of natural enemies of the cotton whitefly in Sudan Gezira

Published online by Cambridge University Press:  19 September 2011

Asim A. Abdelrahman
Asim A. Abdelrahman
Affiliation:
Gezira Research Station, Agricultural Research Corporation, Wad Medani, Sudan
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Abstract

The cotton whitefly, Bemisia tabaci (Genn.), is parasitized by four Aphelinid species: Eretmocerus diversiciliatus Silv., E. mundus Merc., Encarsia lutea Masi. and an unidentified Encarsia sp Whitefly adults move from field weeds onto cotton during the period September–November. The application of broad-spectrum insecticides to control other cotton pests early in the season prevents the establishment of the host-stage of B. tabaci needed by the parasitoids within cotton fields during September and October. The rate of parasitism is consequently decelerated to peak in January towards the end of the season. Peak per cent parasitism for treated cotton fields was 36.7 as compared to 76.8 in untreated fields. This has promoted B. tabaci to an all season pest instead of an early and mid-season occasional pest. Alternative control strategies for early season pests are discussed.

Résumé

La mouche blanche du cotonnier, Bemisia tabaci (Genn.) est infestée de parasites de quatre espèces Aphelinid: Eretomcerus diversiciliatus Silv., E. mundus Mere, Encarsia lutea Masi, et d'une espèce d'Encarsia non-identifiée. Les mouches blanches adultes se déplacent dans leschamps des mauvaises herbes aux cotonniers pendant la période Septembre/Novembre. L'application de large spectre d'insecticides pour enrayer les autres parasites du cotonnier au début de la saison empêche l'établissement du stage d'hôte de la B. tabaci nécessité par les parasites dans les champs de cotonniers pendant la saison de Septembre à Octobre. Par conséquent, le taux de parasitisme est freiené pour n'atteindre son apogée qu'en Janvier vers la fin de la saison. Le taux maximum du parasitisme était de 36,7% pour des champs traités contre 76,8 pour des champs non-traités. Ce qui a promu la B. tabaci au rang de peste permanente pendant toute la saison au lieu d'une peste occasionnelle de début et mi-saison. Des strategies alternatives de lutte contre les pestes de début de saison sont débattues.

Keywords

Bemisia tabaciChrysopa carneawhitefly parasitescotton pestsSudan GeziraBemisia tabaciChrysopa carneaparasites de la mouche blanchepestes du cotonnierSudan Gezira
Type
Research Articles
Information
International Journal of Tropical Insect Science , Volume 7 , Issue 1 , February 1986 , pp. 69 - 73
Copyright
Copyright © ICIPE 1986

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References

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