Regional distribution of Lepidopteran stemborers and their parasitoids among wild grasses in the semi-arid eastern Kenya
| Autor: | William A. Overholt, J. M. Songa, R. O. Okello, J.M. Mueke |
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| Rok vydání: | 2002 |
| Předmět: | |
| Zdroj: | African Crop Science Journal; Vol 10, No 2 (2002) |
| ISSN: | 2072-6589 1021-9730 |
| DOI: | 10.4314/acsj.v10i2.27551 |
| Popis: | (Received 25 April, 2001; accepted 5 March, 2002) ABSTRACT A survey was conducted in six agroecological zones (AEZs) in semi-arid eastern Kenya, in May, 1996, to identify the major wild host grasses (abundance > 70%) for stemborers in each zone. The grasses sampled were Pennisetum purpureum Schumach, P. trachyphyllum Pilg., Panicum maximum Jacq, Sorghum versicolor Anderss, Cenchrus ciliaris L. and Cyperus sp. Among these grasses, P. purpureum was the most widespread and abundant. The survey was followed by an on-farm study conducted in each of the six AEZs to determine the relative abundance and distribution of stemborers, that infested the major wild grasses and their parasitoids . This was done by destructive sampling of 100 tillers, at a three-month interval, from July 1997 to April 1998. The stemborers that infested the grasses were Chilo partellus Swinhoe and Sesamia calamistis Hampson. Among these, C. partellus was the predominant species, with the highest number being recovered on S. versicolor (94.6%). Parasitoids were only reared on S. versicolor, and these were Cotesia sesamiae (Cameron), C. flavipes Cameron, Chelonus curvimaculatus (Cameron), Pristomerus sp. and Norbanus sp., with C. flavipes causing the highest parasitism (13.6%). Results reveal that S. versicolor exhibited potential for use in the management of stemborers in maize, by acting as a "trap" and "refuge" crop for C. flavipes, between cropping seasons. Key Words: Agroecological zones, Chilo partellus, Cotesia flavipes, Cotesia sesamiae, refuge, trap crop Resume Une reconnaissance a ete effectuee dans six zones agro-ecologiques de la region semi-aride du Kenya, en Mai 1996, en vue d'identifier les herbes sauvages dominantes (abundances > 70%) pouvant servir de pieges pour les destructeurs des tiges de mais. Les herbes echantillonnees etaient Pennisetum purpureum Schumach, P. Tranchyphyllum Pilg., Panicum maximum Jacq, Sorghum versicolor Anderss, Cenchrus ciliaris L. and Cyperus sp. La reconnaissance etait appuyee par une etude dans les fermes, dans chaque zone ecologique, pour determiner l'abondance relative et la distribution des destructeurs des tiges et leurs parasites envahissant les herbes dominantes. Pour ce faire, un echantillonnage destructif etait utilise. Cent tiges fraiches etaient coupees a trois mois d'interval, de Juillet 1997 en Avril 1998. Les destructeurs des tiges ayant attaque les plantes etaient Chilo partellus Swinhoe et Sesamia calamistis Hampson. Partellus etait l'espece la plus dominante. Partellus etait abondant sur le S. versicolor. Les parasites se cabraient uniquement sur S. versicolor, parmis eux, Cotesia sesamiae (Cameron), C. flavipes Cameron , Chalonus curvinaculatus (Cameron), Pristomerus sp. et Norbanus . Flavipes C. avait le plus taux de parasitisme (13.6%). Les resultats ont ainsi revele que S. versicolor a un potentiel de control sur les destructeurs de mais en agissant comme piege et refuge au C. flavipes durant les saisons de culture. Mots Cles: Zones agro-ecologiques, Chilo partellus, Cotesia flavipes, Cotesia sesamiae, refuge, plant piege (Af Crop Sci J 2002 Vol 10 No 2 pp183-194) |
| Databáze: | OpenAIRE |
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