Impact of different levels of nitrogen fertilizer on the population dynamics and within plant distribution of Podagrica species and yield of okra

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2014-10-16
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In West Africa, okra cultivation is bedeviled with insect pests’ infestation, especially flea beetles, Podagrica spp. Several studies on population of these pests have been reported but very little literature is available on their seasonal variation and distribution within the okra plant. This research was undertaken with the objective to investigate the population dynamics and within plant distribution of Podagrica spp. on okra as influenced by different levels of N-fertilizer. This research was conducted in the major (April-June) and the minor seasons (July-October) in 2011 at the Plantation Section of the Department of Crop and Soil Sciences of the Kwame Nkrumah University of Science and Technology, Kumasi, Ghana. Okra (Asontem variety) was used; three levels of NPK fertilizer (40-30-30, 50-30-30, 60-30-30) kgha¬-1 and a control (no fertilizer) were imposed as soil amendment in Randomised Complete Block Design with four replications. Plots with the highest dose of N recorded significantly (P<0.05) higher number of Podagrica spp. and higher yield in both seasons despite the increased Podagrica spp. numbers. Plots that received highest dose of N also recorded significantly (P<0.05) number of fruits. Again, significantly (P<0.05) more Podagrica spp. aggregated in the upper canopy than the lower canopy in both seasons. Significantly higher number of Podagrica spp. was collected in the major season than in the minor season. The per cent number of holes in the leaves was significantly (P<0.05) higher in plots that received higher N doses where significantly more Podagrica spp. aggregated. The findings of this study could serve as a guide to design sampling protocol for Podagrica spp. on okra.  
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A thesis submitted to the Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfillment of the requirement for the degree of Master of Science in Crop Protection (Entomology), 2013
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