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Dynamique d'un système hôte-parasitoïde en environnement spatialement hétérogène et lutte biologique Application au puceron Aphis gossypii et au parasitoïde Lysiphlebus testaceipes en serre de melons

Abstract : Natural ecosystems are unavoidably spatially structured and the induced heterogeneity affects various processes of ecological systems. In many cases, the influence of spatial heterogeneity on population dynamics remains unclear. This thesis contributes to a better theoretical understanding of the effects of such heterogeneity on host-parasitoid interactions. In this way, three spatial approaches were developed and adapted to the aphid pest Aphis gossypii and one of its parasitoids Lysiphlebus testaceipes in a melon greenhouse. The importance of spatial structure was tested by comparing a non-spatial model with a spatially explicit model (a lattice one). Our results showed that considering space is essential to describe the spatial heterogeneous distribution of populations observed in the field. The way in which space should be considered was tested by comparing the spatially explicit model with a new implicit approach, which describes the level of plant infestation by a continuous variable corresponding to the number of plants with a given density of pests at a given time. When the explicit model needs as many equations as plants in the greenshouse, our novel approach has only a partial differential equation. We could infer from the comparisons between the two spatial models that the predicted host-parasitoid dynamics were similar under most conditions; and the differences were due to local dispersal (considered only in the explicit model), because it could have a strong impact on population dynamics but did not change the conclusions for crop protection. The new implicit model thus generated relevant predictions with a more synthetic formalism than the common plant-by-plant model. This implicit model was used to test biological control strategies. We showed that (i) preventive releases are less efficient than curative ones, if the cost of infestation detection is not too high; (ii) strategies with several releases are always better than single releases strategies. As a conclusion, we demonstrated that the effectiveness of a biological control depends on the functional response of the parasitoids, the initial distribution of pests (that determines the infestation process) and the costs affected to each type of strategies.
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https://pastel.archives-ouvertes.fr/pastel-00003399
Contributor : Ecole Agroparistech <>
Submitted on : Tuesday, February 12, 2008 - 8:00:00 AM
Last modification on : Tuesday, October 29, 2019 - 11:38:03 AM
Long-term archiving on: : Wednesday, September 8, 2010 - 6:02:49 PM

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Christelle Lopes. Dynamique d'un système hôte-parasitoïde en environnement spatialement hétérogène et lutte biologique Application au puceron Aphis gossypii et au parasitoïde Lysiphlebus testaceipes en serre de melons. Sciences of the Universe [physics]. AgroParisTech, 2007. English. ⟨NNT : 2007AGPT0019⟩. ⟨pastel-00003399⟩

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