Assessment of Tritrophic Interaction between Larval Parasitoid, Cotesia Icipe (Hymenoptera: Braconidae) and Its Key Hosts in Maize Cropping Systems In Kenya

Simple item page
dc.contributor.advisorSamira Mohameden_US
dc.contributor.advisorSubramanian Sevganen_US
dc.contributor.advisorTitus Obidi Magomereen_US
dc.contributor.authorObala, Francis
dc.date.accessioned2024-02-02T11:19:42Z
dc.date.available2024-02-02T11:19:42Z
dc.date.issued2023
dc.descriptionA Thesis Submitted in Partial Fulfilment of the Requirements for the Award of the Degree of Master of Science (Biotechnology) in the School of Pure and Applied Sciences of Kenyatta Universityen_US
dc.description.abstractThe introduction and establishment of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), cause devastating damages to maize crops and major loss to the source of income for millions of maize growers in Africa. Farmers responded to the pest through application of broad-spectrum insecticides, which are not only expensive and face problems of pest resistance, but also pose negative effect to the environment, human health, and kill beneficial insects. Biological control offers safer and sustainable management option against fall armyworm. With the proof that Cotesia icipe (Hymenoptera: Braconidae) was a potential biocontrol agent, there was a research gap on the efficiency of the parasitoid to manage the target pest within maize cropping system in Kenya. Thus, this thesis investigated the tritrophic interactions, involving plants, herbivores, and the natural enemy (parasitoid). To achieve that objective, first, the host range and performance of C. icipe on the target pest, S. frugiperda, and potential hosts, Busseola fusca, Chilo partellus (Swinhoe), Sesamia calamistis Hampson, and Spodoptera littoralis (Boisduval, 1833) (all Lepidoptera: Noctuidae). Second, the parasitism of S. frugiperda by C. icipe reared on different host plants and the effects of the host plants on the quality of the parasitoid progenies was assessed. Third, the behavioural response of C. icipe, in terms of its oviposition choices to maize plants infested by the stemborers and S. frugiperda was also assessed. Lastly, the chemical analysis of organic volatile profile emitted by maize plants due to herbivory by the stemborers and S. frugiperda, as well as the antennal responses of S. frugiperda female moths to the compounds, were also evaluated. The acceptability of the stemborers and Spodoptera species to C. icipe was conducted under no-choice test, whereas its performance on each host, in the presence of all hosts, was done under multiple-choice test. In addition, suitability of the host insects for the development of the parasitoid, and effects of each host larvae on the development and fitness of the parasitoid progenies were evaluated. To test the parasitism and development of C. icipe when it develops in S. frugiperda larvae reared on the different host plants (commonly intercropped with maize), then cocoon formation rate, sex ratio, and fitness of the parasitoid progenies were evaluated. Further, in a Y-tube olfactometer, the response of C. icipe towards stemborers and S. frugiperda- infested maize plants was tested in terms of the parasitoid choices to the chemical cues. Lastly, Gas Chromatography (GC) Mass Spectrometry and GC- electroantennographic detection were conducted on the volatile organic compounds that were extracted from damaged (by stemborers and S. frugiperda) and healthy maize plants on S. frugiperda female moths. The results showed that C. icipe deposited its eggs and successfully developed in all the stemborers and Spodoptera species, albeit with differences in developmental duration, being longest in C. partellus (19.0 ± 0.4 days from egg to cocoon formation), but not significantly different for the duration between cocoon formation and wasp eclosion (4 days) for all the tested hosts. Under no choice test, C. icipe parasitized and successfully completed its life cycle in all the tested hosts; with the highest parasitism recorded in both Spodoptera species (97%) and the least parasitism obtained in C. partellus (24%). In multiple-choice test scenario, highest parasitism was recorded in both S. frugiperda (97%) while the least parasitism was obtained in C. partellus (24%). Moreover, the assessment of encapsulation or melanisation revealed that only 0.05% of C. icipe eggs were encapsulated by C. partellus. For the analysis of the plant odours commonly reported compounds such as linalool, (E)-α-Bergamotene, TMTT, β-caryophyllene, DMNT, (Z)-3-hexen-1-ol, indole and (Z)-3-hexenyl acetate were obtained. Importantly, those compounds elicited antennal response of S. frugiperda females. In conclusion, this study found that using C. icipe in augmentative biocontrol of S. frugiperda in maize cropping system in Kenya is not jeopardized by the co- occurrence of the stemborers with the Spodoptera species, and neither the volatile organic compounds emitted by maize plants nor the existence of different host plants of S. frugiperda affect the parasitoid’s efficiency towards fall armyworm as the target pest.en_US
dc.description.sponsorshipkenyatta universityen_US
dc.identifier.urihttps://ir-library.ku.ac.ke/handle/123456789/27467
dc.language.isoenen_US
dc.publisherkenyatta universityen_US
dc.subjectTritrophicen_US
dc.subjectLarval Parasitoiden_US
dc.subjectCotesia Icipe (Hymenoptera: Braconidae)en_US
dc.subjectMaize Cropping Systemsen_US
dc.subjectKenyaen_US
dc.titleAssessment of Tritrophic Interaction between Larval Parasitoid, Cotesia Icipe (Hymenoptera: Braconidae) and Its Key Hosts in Maize Cropping Systems In Kenyaen_US
dc.typeThesisen_US
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Assessment of Tritrophic Interaction between Larval Parasitoid.pdf
Size:
1.82 MB
Format:
Adobe Portable Document Format
Description:
fulltext thesis
Download
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
license.txt
Size:
1.71 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
MST-Department of Biochemistry and Biotechnology