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Geographical distribution, population density and host plants of tef epilachna Chnootriba similis (Coleoptera: Coccinellidae) in Ethiopia

Published online by Cambridge University Press:  01 September 2006

Yibrah Beyene ,
Trond Hofsvang ,
Ferdu Azerefegne  and
Trygve Berg
Yibrah Beyene*
Affiliation:
Norwegian University of Life Sciences, Department of Plant and Environmental Sciences, PO Box 5003, N-1432 Ås, Norway
Trond Hofsvang
Affiliation:
Bioforsk, Høgskoleveien 7, N-1432 Ås, Norway
Ferdu Azerefegne
Affiliation:
Debub University, Awassa College of Agriculture, PO Box 5, Awassa, Ethiopia
Trygve Berg
Affiliation:
University of Life Sciences (UMB), NORAGRIC, PO Box 5001, N-1432 Ås, Norway
*
*E-mail: [email protected]
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Abstract

A survey on the geographical distribution of Chnootriba similis (Thunberg), formerly known as Epilachna similis, was undertaken from 2001 to 2003 in the main cereal-growing areas of Ethiopia. The population density of the insect was estimated by sweep netting (100 sweeps/farm). In addition, more detailed studies on seasonal and annual fluctuations in population density of C. similis were carried out in southern Ethiopia between 2002 and 2003 by sampling 10 quadrants of 0.25 m2 per farmer's field. The damage levels were determined using scores of 0–9. The survey revealed that C. similis is widely distributed in different parts of the cereal-growing regions of Ethiopia. It was observed that the beetles had spread to altitudes ranging from 1217 to around 3000 m asl. However, the variations in population densities of C. similis cannot be directly attributed to altitude, as highly differing population densities in similar altitudes of different locations were recorded. Annual and seasonal variations in population density were observed in different areas of the southern part of Ethiopia. These results suggest that C. similis has a sporadic nature and can occasionally build up to outbreak levels. Beetles fed on both cereals (barley, wheat, tef, maize, sorghum and finger millet) and wild grasses (Leersia hexandra (Sw.), Avena abyssinica (Hoechst) and Lolium temulentum (L.)). Population densities and damage levels on the cereal crops varied considerably with the highest densities and damage levels on barley.

Résumé

Une enquête sur la distribution géographique de Chnootriba similis (Thunberg), connu auparavant sous le nom d'Epilachna similis, a été menée de 2001 à 2003 dans les principales régions céréalières d'Ethiopie. La densité des populations de l'insecte a été estimée par des coups de filet (100 coups/ferme). Par ailleurs, une étude plus précise des fluctuations saisonnières et annuelles de la densité des populations de C. similis a été menée dans le sud éthiopien en 2002 et 2003 en échantillonnant 10 quadrants de 0,25 m2 par parcelle. Le niveau des dégâts a été estimé à l'aide d'une échelle de 0 à 9. L'enquête indique que C. similis est commun dans la plupart des régions céréalières d'Ethiopie. On a constaté que la coccinelle a colonisé des altitudes comprises entre 1217 et 3000 m. Cependant, les variations de densité de populations de C. similis ne peuvent s'expliquer par l'altitude seule dans la mesure où des différences de densité très importantes ont été constatées à une même altitude. Des variations saisonnières et annuelles de densité de population ont été observées dans différentes zones du sud de l'Ethiopie. Ces résultats suggèrent que C. similis a une nature sporadique et peut occasionnellement pulluler. La coccinelle se nourrit aussi bien de céréales (orge, blé, tef, maïs, sorgho et mil), que de graminées sauvages (Leersia hexandra (Sw.), Avena abyssinica (Hoechst), Lolium temulentum (L.)). Les densités de population et le niveau de dégâts sur les céréales cultivées varient considérablement, les plus fortes densités de populations et le niveau de dégâts le plus élevé étant observés sur orge.

Keywords

Chnootriba similisdistribution géographiquecéréalesplantes hôtesniveau de dégâtsdensité de populationEthiopieChnootriba similisgeographical distributioncerealshost plantsdamage levelspopulation densityEthiopia
Type
Research Article
Information
International Journal of Tropical Insect Science , Volume 26 , Issue 3 , September 2006 , pp. 183 - 189
Copyright
Copyright © ICIPE 2006

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