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The role of local natural enemies in population dynamics of Chilo partellus (Swinh.) (Pyralidae) under subsistence farming systems in Kenya

Published online by Cambridge University Press:  19 September 2011

G. W. Oloo
G. W. Oloo
Affiliation:
International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya
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Abstract

The present article is one of a series of papers in preparation in which an ecological approach to developing a sound biocontrol programme for cereal stem borers is proposed and outlined. The proposed approach involves detailed population estimation and analysis in relation to crop phenology to determine the role of local natural enemies, evaluation of biocontrol potential of promising biocontrol agents, developing mass rearing and release technology and monitoring the impact of the biocontrol programme. In the example used to illustrate the first step in such a programme, life table analysis of data from a 2-year study on Chilo partellus on maize and sorghum under subsistence agriculture in Western Kenya, showed local predators (and unidentified factors) to contribute up to 97.6 % of generation mortality of the borer in the age interval from egg to early instar larva, while parasitoids and pathogens contributed less than 1 % mortality in the various life stages. Hence, a programme involving conservation and augmentation of local predators and introduction of selected exotic parasitoids of this borer seems appropriate. This represents an attempt to apply life table analysis, taking into account plant phenology, in studying interacting populations under subsistence farming conditions.

Résumé

Ce present article fait parti d'une serie en preparation, dans laquelle une approche ecologique de lutte biologique appropriée contre les forreurs a èté developpée. Cette approche involve une estimation detaillée de la population et son analyse en relation avec la phenologie des cultures pour determiner le role des ennemies naturelles locaux. D'autre part cette analyse comprend l'evaluation des agents prometteurs pour la lutte biologique, le developpement de production en masse de ces derniers et leur technique de lacher ainsi que l'evaluation de l'impact du programme de lutte biologique. Dans cette exemple, l'analyse de la table de vie d'une etude d'une durée de deux ans sur le Chilo partellus et les cereales suivants maïs et sorgho sous des conditions d'agriculture de subsistance à l'ouest du Kenya, a demontrée que les predateurs locaux (et des facteurs non identifies) contribuaient 97.6% du taux de mortalitè (entre les ouefs au premier stage larvaire) d'une generation des forreurs. Les parasitoides et les pathogenes de leur côté contribuaient moins de 1% de la mortalité des differents stages de developpement. De ce fait un programme qui doit comprendre la concervation et l'augmentation des predateurs locaux et l'introduction des parasitoides exotiques selectionnés de ces forreurs pourra être approprier. Cette etude represente la mise en application de l'analyse d'une table de vie, qui prend en compte la phenologie des plantes en se basant sur l'interaction entre des populations sous des conditions d'agriculture de subsistance.

Keywords

Population dynamicsChilo partelluslocal natural enemiesecological life tablesbiocontrolsubsistence farming systems
Type
Research Article
Information
International Journal of Tropical Insect Science , Volume 10 , Issue 2 , April 1989 , pp. 243 - 251
Copyright
Copyright © ICIPE 1989

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References

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