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Title: Using companion plants to enhance biological control of the cabbage moth, Mamestra brassicae (L.)
Author: Geneau , Celine Emelyne Elodie
Awarding Body: Lancaster University
Current Institution: Lancaster University
Date of Award: 2012
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Parasitoids play a fundamental role in the regulation of herbivore pests in natural settings. Flower resources can be used to provide natural enemies with suitable food sources that are otherwise lacking in modern agro-ecosystems, in order to enhance biological pest control. However, the introduction of flower resources can also enhance the fitness of the pests. This thesis investigated the potential of floral resources in enhancing the biological control of the cabbage moth Mamestra brassicae (L.) (Lepidoptera: Noctuidae) by its main parasitoid Microplitis mediator (Haliday) (Hymenoptera: Braconidae). A thorough review of available data showed that most parasitoids strongly depend on adult feeding for survival and that some flower species are selective, i.e. they only enhance the fitness of the parasitoids and not the pests. I performed laboratory experiments to identify selective flower species that enhance the fitness of M mediator, without benefiting its host, M brassicae. Longevity and parasitization rates by M mediator increased significantly with Centaurea cyanus, Fagopyrum esculentum and Vicia sativa. Longevity and fecundity of the pest were not affected by the plant species tested. I further studied the ability of M mediator to locate extrafloral nectar of C. cyanus. Female M mediator showed an innate attraction to olfactory cues of floral but not extrafloral nectar of C. cyanus. The most promising plant identified, C. cyanus, was assessed with regard to its effect on parasitization rates of M brassicae and crop yield in a two-year large-scale replicated field experiment. Parasitization rates of M brassicae significantly increased in the treatment with C. cyanus, resulting in a significant increase in the marketable cabbage weight in this treatment in 2009. These results emphasize the importance of plant screening in identifying selective plant species and underline the potential of flowering companion plants as new habitats, resulting in an increase in the success of biological control programs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available