Modelling The Impact Of Climate Change On The Maize Stem Borer Communities And Their Main Natural Enemies Along Altitudinal Gradients In East Africa

Abstract

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 changes. 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 changes 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.