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Thesis started november 1^st, 2016. Defended in december 2019, 17th
Fund: FEADER PEI-AGRI, Conseil Régional de Bretagne
Direction: Bruno Jaloux et Sylvia Anton

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Abstract:

The diversity of resources available for consumers determines a wide range of ecological processes, from individual behavioural strategies to community structure. Intercrops and single crops are an ideal model to study the relationship between resource diversity and their use by parasitoids insects. As intercrops provide resources such as alternative hosts or food sources for parasitoids, they could also allow enhancing biological control. In this thesis, we study the relationship between resource diversity and their exploitation by Aphidius spp. aphid parasitoids in legume and cereal single crops and intercrops. First, we investigate how early learning influences host selection in Aphidius ervi. We reveal that olfactory complexity experienced by the insect influences its subsequent preferences, but also that olfactory preferences are not sufficient to fully explain its foraging decisions among different hosts. Then, we evaluate the resource use patterns of Aphidius spp. communities in nectar-depleted fields (single crops) and nectar-complemented fields (intercrops). We show that honeydew is a major food source for Aphidius spp. parasitoids in cereal crops, and that nectar providing does not seem to change their resource exploitation patterns. We also find no effect of intercropping on aphid parasitism rates and biological control. Altogether, our results show that resource diversity is an important feature that drives individual behaviour, but that its influence does not systematically affect processes at the population or community scale. Other factors, such as resource density, may better explain such processes. Besides, we could not evidence a beneficial effect of intercropping on biological control. However, other approaches will be needed to better evaluate the potential of such crops for pest regulation and to identify the ‘right forms of biodiversity’ for conservation biological control.  

Poster pdf