9: Characterizing the honeydew microbiota of the invasive sugarcane aphid

The sugarcane aphid (Melanaphis sacchari Zehntner, SCA) is a serious pest of sorghum across the continental USA. Recently, our research team found differences in natural enemy presence between SCA feeding on grain sorghum and Johnson grass. Bacterial microbiota of honeydew from other aphid species are reported to influence the attractiveness of honeydew to natural enemies and ants. We hypothesize that sugarcane aphid diet (i.e., sorghum or Johnson grass) may influence SCA honeydew bacterial composition. Differences in SCA honeydew bacterial composition may explain the observed differences in natural enemy abundances on grain sorghum versus Johnson grass. Honeydew of SCA was collected by placing aphid clones in clip cages affixed to a host plant and inserting a preweighed plastic disc at the bottom of the clip cage to catch honeydew droplets. Since honeydew can be differentially colonized by microbes across time, we also compared microbial composition at three collection time points (24 hrs, 72 hrs, 120hrs). Honeydew samples were extracted using a DNeasy PowerSoil Kit and samples were sequenced for the V4 region of 16s ribosomal RNA. We found some differences in microbial composition between aphids on sorghum and Johnson grass. Ongoing bioassays are testing the attractiveness of honeydew with different bacterial compositions for SCA parasitoids. Our research is improving our understanding of how honeydew microbiota composition is influenced by diet and time and how this may play a role in natural enemy and ant recruitment. This knowledge may provide novel pest control targets to improve SCA management in sorghum fields.