The rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae ), vectors microbes when they arrive in new food patches regardless of dispersal period or source patch

Understanding how insects may vector microbes during movement is central for pest management. Our lab has found insect infestation in grain after harvest changes the microclimate to benefit both insects and microbes, but few studies have evaluated whether and how stored product insects may vector microbes among food facilities or patches. It is also unknown whether the length of time between dispersal from one foraging patch to another (e.g. dispersal period) influences the propensity to vector microbes. Thus, we evaluated the ability of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) from different populations to vector microbes by placing single individuals on sterilized agar (novel food patch) after differing dispersal periods. Adults were wild-caught, removed from lab colonies, or from Aspergillus flavus-inoculated grain and introduced immediately into separate petri dishes with potato-starch agar (0 h) or placed in a UV-sterilized airtight container and given the opportunity to disperse for 24 h, or 72 h, then placed on agar dishes. Plates were assessed after movement by S. oryzae for 3 or 5 d on agar by noting whether trails of microbes are visible, photographing the dishes, then analyzing the microbial imprints (percent of dish covered) with ImageJ. We found that in most cases there were clear trails of microbes, though percent cover by microbes depended on source population of insects but not dispersal period, suggesting that insect-mediated dispersal facilitated microbial contamination of new food patches. We conclude that insects and microbes may need to be managed together in comprehensive IPM programs.