Interactions between the root rot pathogen Fusarium avenaceum and the pea leaf weevil (Sitona lineatus) in field pea

Abstract

Root rot caused by Fusarium spp. and nodule herbivory by larvae of the pea leaf weevil, Sitona lineatus, are major factors constraining the production of field pea (Pisum sativum). Interactions between these pests have the potential to increase plant injury and yield loss, but have not been explored. In this study, the relationship between F. avenaceum and larval S. lineatus was evaluated in greenhouse trials. An apparently mutualistic interaction was observed when both species co-occurred in pea roots, in which disease pressure increased and larval mortality decreased. Larval feeding wounds may have facilitated infection by serving as entry points for F. avenaceum. It is not clear why F. avenaceum decreased insect mortality, but fungal detoxification of pea phytoalexins is discussed as a potential mechanism. These results will serve as a basis for further investigation of these interactions under field conditions, and suggest that integrated crop protection measures will be critical in regions where F. avenaceum and S. lineatus co-occur.