Influence of the cultivated plant diversity on the abundance of arthropod trophic groups and Helicoverpa armigera biological control in tomato cropping systems in Benin

With the aim of optimizing pest management, a study was carried out to determine the effect of cultivated plant diversity on arthropod communities and Helicoverpa armigera regulation in tomato cropping systems. Therefore, the diversity of cultivated plants and arthropod communities were assessed within and around tomato fields from 30 farmer’s fields randomly selected in South of Benin. In each tomato field, an experimental plot (or elementary plot) (20x20m) in the center of each tomato field was delimited. Each experimental plot was subdivided into a 4 m by 4 m quadrats in which all cropped plants were identified and counted. In the center of each quadrat, one Pitfall trap with soapy water leading to 25 Pitfall traps per field was placed and uplifted after 72 hours to capture the soil and litter macrofauna. The study showed that at the field scale, the abundances of omnivore predators, generalist predators and herbivores were greater in mixed cropping systems than in monocropping systems while the abundance of Helicoverpa armigera was lower in the mixed cropping systems than in monocropping systems. Multiple intercropped plant species increased the abundance of generalist and omnivore predators. This study allowed better understanding how plant diversity associated to tomato field structures arthropod food webs to finally enhance the ecological management of H. armigera.