Résumé
In an attempt to develop alternative protection methods for sugar beet (Beta vulgaris) crops against yellows viruses and their main vector, the green peach aphid Myzus persicae Sulzer (Aphididae, Macrosiphini), we evaluate the potential of companion plants to attract or repel this aphid species. Host selection experiments in the laboratory revealed a strong preference of M. persicae for Chinese cabbage (Brassica rapa, subsp. pekinensis) over sugar beet plants, whereas sugar beet plants were strongly preferred over oat (Avena strigosa). These effects were confirmed in field experiments where sugar beets associated with oat were significantly less infested by aphids than control sugar beets, and Chinese cabbage hosted higher numbers of aphids and reduced numbers of wingless aphids at short distance. However, infection of sugar beets by yellows viruses was only reduced early in the season in plots with oat. In the other types of plots, infection was not reduced, and viruses were present in a large proportion of the sugar beet plants independently of the companion plant associated with beet. Our study shows that in spite of Brassicaceae and oat being promising candidates for a push–pull strategy controlling green aphid populations in the field, limited reduction of virus infection on sugar beets calls for further studies on the origin of yellows virus epidemics.