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Thesis started november 2017. Defended in july, 2020 11^th
Funding: CIFRE
Direction: Anne Le Ralec - Yannick Outreman

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Abstract

Inundative biological control consists in mass-rearing natural enemies of crop pests and releasing them in an agroecosystem to regulate pest populations. While this technique is widespread for some greenhouse crops, sometimes it does not ensure an efficient pest control. This is the case for biological control of aphid pests in protected strawberry crops. The objective of this thesis was to study the ecological interactions among pests and their natural enemies in order to identify the ecological and evolutionary factors that could explain the failure of a biological control program. By studying aphid and parasitoid communities and their trophic networks, we identified parasitoid species adapted to control aphids and potential indirect interactions that could limit biological control efficiency. Moreover, we showed that aphids in strawberry greenhouses were often infected with bacterial symbionts that may confer a protection against the released parasitoids. Finally, a population genetics study of both wild and mass-reared parasitoids indicated a genetic differentiation between commercial and wild parasitoids. This genetic differentiation being associated with a loss of genetic diversity within commercial populations, this raises the question of their efficiency against the targeted aphid pests. All these results allow considering possible solutions to improve biological control in protected crops.

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