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Timing and Distribution of Attack by the Banana Weevil (Coleoptera: Curculionidae) in East African Highland Banana (Musa spp.)

A. M. K. Abera, C. S. Gold and S. Kyamanywa
The Florida Entomologist
Vol. 82, No. 4 (Dec., 1999), pp. 631-641
DOI: 10.2307/3496480
Stable URL: http://www.jstor.org/stable/3496480
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Timing and Distribution of Attack by the Banana Weevil (Coleoptera: Curculionidae) in East African Highland Banana (Musa spp.)
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Abstract

Timing and distribution of attack on East African highland banana (Musa AAA-EA) by the banana weevil, Cosmopolites sordidus (Germar), (Coleoptera: Curculionidae) was studied in a field trial at a farm 25 km NE of Kampala, Uganda. Weevils were released at three densities (5, 20 and 40 females per mat) in 324 m2 banana plots (cv Atwalira) that had been established 18 months earlier and maintained relatively free of weevils. Two weeks after release, entire mats were removed and examined for weevil eggs and first instar larvae. At a density of 20 weevils per mat, oviposition occurred on 25% of plants less than 6 six months old (suckers) with an average of three eggs (range 0-16) per infested plant. At the same time, 85% of flowered plants were attacked with mean oviposition of 15 eggs (range 0-41) per plant. An inverse relationship existed between weevil population density and eggs/female/plant. Five females per mat produced an average of 7.2 eggs per flowered plant, whereas 20 females produced 15 eggs per flowered plant and 40 females produced 12.5 eggs. This suggests the existence of density-dependent factors in weevil oviposition. Over 90% of the oviposition occurred in the base of the pseudostem, with the remaining eggs found in the corm and roots near the soil surface. However, in stands displaying high mat, (a condition in which part of the corm appears above the soil surface) more eggs were found on the corm than pseudostem. /// Se estudió la época y distribución del ataque del barrenador del plátano, Cosmopolites sordidus (Germar), (Coleoptera: Curculionidae) al plátano de montaña de Africa del Este (Musa AAA-EA) en una plantación ubicada 25 km al NE de Kampala, Uganda. Se liberaron tres densidades de barrenadores (5, 20, y 40 hembras por mata) en lotes de 324 m2 del cv. Atwalira plantados 18 meses antes y mantenidos relativamente libres de barrenadores. Dos semanas despues de liberar los barrenadores, se examinaron matas completas para determinar la presencia de huevecillos y larvas en primer instar. La densidad de 20 hembras/mata resultó en oviposición (0-16 huevecillos/planta) en 25% de plantas de menos de 6 meses de edad (chupones). El 85% de las plantas con floración fueron atacadas, encontrándose un promedio de 15 huevecillos/planta (rango 0-40 huevecillos/planta). Se encontró una relación inversa entre la densidad de población del barrenador y la cantidad de huevecillos/hembra/mata. La densidad de 5 hembras/mata resultó en un promedio de 7.2 huevecillos/planta florecida, mientras que 20 y 40 hembras/mata produjeron 15 y 12.5 huevecillos/planta florecida, respectivamete. Los resultados sugieren que el nivel de oviposición depende de la densidad de hembras. Mas del 90% de la oviposición ocurrió en la base del pseudotallo, mientras que el resto de los huevecillos se encontró en el cormo y raices cercanas a la superficie del suelo. Sin embargo, en aquellas plantas con cormos ubicados arriba de la superficie del suelo, se encontraron más huevecillos en el cormo que en el pseudotallo.

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