Distribución y fluctuación estacional del trips de la flor (Thysanoptera: Thripidae) en la judía (Phaseolus vulgaris L.) en Kenia

The aim of this research was to study spatial distribution of flower thrips on French beans (Phaseolus vulgaris L.) in Kenya. Their build up and seasonal population dynamics was monitored using sticky blue colour traps and sampling of leaves and flowers in two seasons in 2002. Thrips infested French beans from the second week after crop emergence. Their population peaked at peak flowering. The sticky trap catches were linearly related to the actual presence of thrips on the crop and could estimate population build up of adult thrips on leaves and flowers. On the plants, most adults were on flowers. Larvae mainly inhabited leaves, buds and pods. The two thrips species, Frankliniella occidentalis (Pergande) and Megalurothrips sjostedti Trybom were spatially separated. The former colonized lower-canopy leaves and early flowers while the latter inhabited middle-canopy leaves and mature flowers. Overall, M. sjostedti was less than 5% of the total thrips population, implying that F. occidentalis was the main thrips pest of French beans. This study suggests that French bean growers should monitor thrips population before initiating any control measure. In addition, they should commence thrips control early, at pre-flowering, using larvicides to reduce the thrips pool and their migration to flowers. A combination of monitoring with sticky traps and proper sampling would contribute to sustainable thrips management.El presente estudio trató de determinar los patrones de alimentación del trips de la flor como plaga de la judía (Phaseolus vulgaris L.) en Kenia. El incremento de la población y grado de infestación de trips se evaluó usando trampas de adherencia azules en hojas y flores durante dos estaciones en el 2002. Los trips infestaron a la judía desde la segunda semana después de la emergencia del cultivo, y alcanzaron una población máxima durante la floración. Conteos en las trampas de adherencia mostraron una correlación lineal con la presencia de trips en el cultivo y pueden servir de referencia del crecimiento de las poblaciones de trips adultos en hojas y flores. En la planta, la mayoría de adultos se encontraron en las flores, mientras que las larvas se concentraron en las hojas, brotes y vainas. Las especies de trips Frankliniella occidentalis (Pergande) y Megalurothrips sjostedti Trybom se mantuvieron separadas en el espacio: mientras que la primera prefiere las hojas inferiores del dosel y las flores jóvenes, la segunda suele optar por las hojas de en medio del dosel y flores maduras. M. sjostedti representa menos del 5% de la población total de trips, lo que hace de F occidentalis la principal peste de la judía. El estudio sugiere que los agricultores deben monitorizar la dinámica poblacional de los trips antes de efectuar medidas de control, y complementariamente, deberían usar larvicidas antes de la floración previendo su posterior migración a las flores. Una adecuada combinación entre vigilancia y adecuada toma de muestras contribuiría al control sostenible de las poblaciones de trips

Model-based estimation of finite population total in stratified sampling

The work presented in this paper concerns the estimation of finite population total under model – based framework. Nonparametric regression approach as a method of estimating finite population total is explored. The asymptotic properties of the estimators based on nonparametric regression are also developed under some specified conditions. An empirical study is undertaken to test the practicability of the theories developed using real data from the Kenya Population and Housing Censuses of 1989 and 1999 Keywords: kernel smoothers, nonparametric, separate ratio estimator > East African Journal of Statistics Vol. 1 (1) 2005: pp. 23-4

Conceptualisation and measurement challenges in modelling pastorilists’ risk and vulnerability instigated by droughts in the group ranches of Kenya

This on-going study is assessing and modeling vulnerability and risks faced by pastoral communities in the dry areas of Lakipia in Kenya. Preliminary results from participatory rural appraisal indicate that poverty is widespread and the area suffers from frequent drought, water shortage, shortage of pasture, livestock diseases and predation and animal human conflicts. More indepth analysis and modeling are still to be don

Space, Culture and Society in Africa.

15 Papers presented at the Symposium, March 29-30, 1996.Includes bibliographical references