Impact de l’aménagement du paysage et des pratiques agricoles en culture de céréales d’hiver sur les populations de parasitoïdes de pucerons

Details

Supervisors

Hance, Thierry

Faculty

Faculté des sciences

Degree label

Master [60] en sciences biologiques

Abstract

enIn a context where intensive agriculture weakens natural regulation processes, biodiversity-friendly practices, such as organic farming or the establishment of vegetative field margins, are often promoted to support natural enemies of pests, particularly aphid parasitoids. To better understand the effects of landscape management and agricultural practices on these parasitoids, this thesis is part of two complementary projects: the university thesis of Emma Servais and the European Biodiversa project. The aim of this study is to assess the effects of farming type (organic vs. conventional) and landscape features (margin types: flower strips, grassy strips, hedgerows, and flower strip–hedgerow combinations) on the activity and diversity of parasitoid wasps in winter cereal fields in Wallonia. Two methods were used: a standardized plant trap experimental setup (thesis) and field transects (Biodiversa + thesis). Results showed no significant effect of farming type on parasitoid activity or diversity, although a higher parasitism rate was observed in organic fields. Flower-based margins (flower strips and flower strip–hedgerow combinations) also showed no significant effect, while grassy strips and hedgerows were more favorable to parasitoid activity and diversity. Although these results should be interpreted with caution due to the low number of mummies collected, the high variability between sites, and unfavorable weather conditions, certain trends suggest that the lack of effect of farming type on parasitoid activity could result from opposing mechanisms related to nitrogen levels in the field. In conventional agriculture, despite pesticide use, higher nitrogen fertilization may increase plant nutritional quality, promoting greater aphid diversity and, consequently, greater parasitoid diversity, potentially offsetting the negative impact of chemical inputs. Conversely, organic farming, while promoting biodiversity, often hosts a more restricted and specialized aphid community, leading to more targeted but fewer trophic interactions. Moreover, the effectiveness of flower strips would appear to strongly depend on their floral composition and functional attractiveness to parasitoids.