Agro-ecological infrastructures for better control of aphid-borne sugar beet viruses

One way of improving the control of aphid vectors of yellows in sugar beet is to optimize conservation biocontrol. Setting up or maintaining agro-ecological infrastructures in or near plots is a good potential lever. The natural enemies of Myzus persicae and Aphis fabae aphids are numerous, ranging from specialist Braconid parasitoid hymenopterans to generalist predators such as spiders, ladybugs, hoverflies, lacewings and carabid beetles. They can all benefit from these agro-ecological infrastructures in terms of shelter and food sources. As part of France's plan to reduce the use of synthetic pesticides (PNRI), we set up three experiments to study the role of flower strips in controlling virus-vector aphids. The first study aimed to quantify, in a semi-controlled environment, the respective actions of epigeous (e.g., carabids) and flying (e.g., parasitoids) natural enemies on aphid colonies, whether or not they were close to a flower strip. A second study aimed to identify the diet of the main predators found in sugar beet fields with or without a flower strip, using molecular tools. Finally, a field monitoring study carried out at the scale of the beet production basin in France compared the aphid control potential at different distances from a flower strip or a control grass strip, and highlighted the significant modulation of the effectiveness of flower strips by the landscape surrounding the plots. Taken together, these three experiments give us a clearer idea, which can be generalized on a large scale, of the mechanisms and potential for action of flower strips, through natural enemies, in controlling aphids.