The production of cereals, especially maize, which is a staple food in sub-Saharan
Africa, is challenged by pests and diseases. In addition, climate change will exacerbate
the magnitude of these challenges and agriculture in general. Lepidopteran stemborers
are major pests of cereal crops in sub-Saharan Africa. Two indigenous noctuids,
Busseola fusca and Sesamia calamistis and one exotic crambid, Chilo partellus, occur
as single and mixed-species communities infesting cereal crops in East and southern
Africa. The composition of these communities however varies with altitude and over
seasons. Interactions between the species especially when in combination, can affect
the level of damage to cereal crops. The objective of this study was to describe the
intraspecific and interspecific interactions between the three stemborer species when
they make use of the same resources. This study involved field surveys in maize fields
in major agro-ecological zones and also different experiments under greenhouse and
laboratory conditions to describe the interactions between the species as well as the
effect of temperature, species density and duration of the period of competition on
outcomes of these interactions. Results showed that stemborer communities are
composed of single and mixed species of B. fusca, S. calamistis and C. partellus, which
varied with the different agro-ecological zones and also along altitudinal gradients.
Temperature was the most important abiotic factor that influenced the composition of
stemborer communities. However, infestation patterns varied with season. This study
also showed that female moths of the three species did not avoid oviposition on plants
that were previously infested by stemborers. Busseola fusca showed a high preference
for heterospecific-infested plants, while C. partellus preferred conspecific-infested
plants. Sesamia calamistis did not show a significant preference for one plant over the
other. This study further showed that both intra- and interspecific competition
characterise communities of these stemborer species which ultilise the same resources.
Interspecific competition was stronger between the noctuids and the crambid than
between the two noctuid species. Temperature had a significant influence on the
competitive outcomes between the three species. Finally the study showed that densitydependent
effects and the duration of the interactions are also important factors which
influence the level of competitive outcomes between the species. Climate change is
likely to influence the interactions and composition of stemborer communities. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/15899 |
| Date | January 2015 |
| Creators | Ntiri, Eric Siaw |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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