Browsing by Author "Mwalusepo, Sizah"

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    Evaluation of Continuous Host-Parasitoid Models
    (University of Dar es Salaam, 2010) Mwalusepo, Sizah
    ln this dissertation the performance of continuous host-parasitoid models were investigated. The parameter values for several well-known models: Lotka-volterra, Holling Type 2. Holling Type 3, Leslie-Gower. Bazykin, Beddington-DeAngelis. Yodzis and Rosenzwing- MacArthur Models were estimated. The models were tested on 40 consecutive sets of time series data collected at 1 4 days interval for pest and parasitoid population obtained from a highland cabbage growing area in Eastern Kenya. model parameters were estimated from the minimization of the loss functions between the theoretical and experimental series datasets following the Nelder-Mead multidimensional method. Initial values of population size andparameters were randomly chosen. Durbin-Watson statistic was applied for comparison of model outputs and experimental population trajectories. Among theeight different host-parasitoid model. Holling type 3 model presented relatively betterapproximation compared to the Other models.
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    Modeling the impact of climate change on the maize stem borer communities and their main natural enemies along attitudinal gradients in East Africa
    (University of Dar es Salaam, 2016) Mwalusepo, Sizah
    Maize is one of the most important staple foods in East Africa. In spite of its importance, maize production in the region faces increased risk of being attacked by maize stem borers due to climate change. This thesis aims at modelling the impact of climate change on the distribution and abundance of two maize stem borers crambid Chilo partellus (Swinhoe), noctuid Busseola fusca (Fuller), and two of their main natural enemies; Cotesia flavipes and Cotesia sesamiae Cameron at local scale along Mount Kilimanjaro and the Taita Hills transects in Tanzania and Kenya, respectively. Mathematical models for the impact of the climate change on the distribution and abundance of the maize stem borers and their natural enemies are adapted and/or developed, simulated and the data obtained both from model simulation and from field and laboratory experiments are analysed. Analysis of the data reveals three main changes occurring simultaneously: (1) Spread of the maize stem borers and their natural enemies to higher altitude areas of the gradients due to climate change; (2) Increase in abundance (number of generations) of both maize stem borers at all altitudes, most importantly by year 2055 predictions, suggest that Chilo partellus and Busseola fusca will cause more damage in the most productive maize zones of both Mount Kilimanjaro and Taita hills; (3) Disruption of the geographical distribution between the maize stem borers and their main natural enemies suggesting improvement of biological control of maize stem borers by both Cotesia flavipes and Cotesia sesamiae. The findings also indicate that both climatic factors and soil characteristics are important in determining the potential distribution of maize stem borers.