Analyse des déterminants des attaques de Meligethes aeneus (Coleoptera, Nitidulidae) et de sa régulation biologique à l'échelle d'un paysage agricole: contribution à l'amélioration de la protection intégrée du colza.

Abstract : Studying the effects of crop management and landscape context on pest populations and natural pest control at multiple spatial scales is a pre-requisite for developing innovative crop protection strategies and increasing the sustainability of agroecosystems. The aim of this study was to explore the relative importance of oilseed rape crop management and landscape context on pollen beetle (Meligethes aeneus Fabr.) density, damage and parasitism rates by its main parasitoids Tersilochus heterocerus, Phradis morionellus and P. interstitialis. In our multi-scale analysis we found that pest abundance and crop damage were mainly determined by and positively correlated with landscape complexity at scales ranging from 1500 m to 2000 m. The positive effect of landscape complexity on pollen beetle density and crop damage in our study region was due to the role of seminatural habitats for overwintering. Pollen beetle damage was also affected by local management as it was negatively correlated with the nitrogen nutrition status of the plants. We found that various variables at different spatial scales influenced parasitism rates. Parasitism rates were positively influenced by landscape complexity, proximity to previous year oilseed rape fields and the proportion of these latter with reduced tillage. By comparing the nutritional state of parasitoids at the time of emergence and foraging in the field, we found that parasitoids emerge with relatively small amounts of sugars and that the total amount of sugars at the end of flowering was always significantly higher than the total amount of sugars at the beginning of flowering. Finally, by studying the accuracy of simple landscape indicators to predict pollen beetle infestations and successful biological control, we found that some indicators were informative and had good discriminatory ability. Using indicators values, optimal thresholds and posterior probabilities, we were able to compute maps of areas at risk for pest infestation and/or allowing successful biological control of pollen beetle. Our study demonstrated the importance of taking into account both farming practices and semi-natural habitats scattered in the landscape to understand population dynamics and biological control in agroecosystems. Our findings open new perspectives in terms of integrated pest management strategies maximizing biological control at the landscape scale.
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Submitted on : Monday, May 2, 2011 - 11:57:52 AM
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Adrien Rusch. Analyse des déterminants des attaques de Meligethes aeneus (Coleoptera, Nitidulidae) et de sa régulation biologique à l'échelle d'un paysage agricole: contribution à l'amélioration de la protection intégrée du colza.. Ecosystèmes. AgroParisTech, 2010. Français. ⟨NNT : 2010AGPT0094⟩. ⟨pastel-00589802⟩

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