Gut-content analysis to determine previous host plants of Leptoglossus zonatus infesting California orchards

Leptoglossus zonatus (Dallas), feeds on multiple weeds and crops across California. In the San Joaquin Valley, they are a pest of more than 20 crops and especially problematic in almonds, pistachio, and pomegranate. Leaffooted bug adults overwinter in aggregations in sheltered areas. In the spring, they migrate into almond orchards to feed on early developing nuts, then move on to pistachio orchards and finally pomegranate. In all cases, feeding on nuts/fruits reduces crop yield and quality. This pest also utilizes other weeds and crops, the extent of which is unclear. As such, understanding alternate host plant use would provide new information on leaffooted bug ecology and potentially help growers predict infestations. Here, we describe the implementation of DNA gut content analysis for L. zonatus. Gut content analysis involves sequencing barcode genes from plant DNA isolated from the guts of leaffooted bug adults, allowing for the retroactive identification of previous hosts. In this work we established protocols for L. zonatus dissection, gut content/DNA extraction, and amplification of the barcode trn-F intergenic spacer. Further, we applied these protocols to lab reared and field collected specimens to identify their past hosts. Preliminary data show that host plant sequences were successfully amplified and identified to the genus/species level from adult L. zonatus. Additional studies are now underway to better characterize DNA retention in the L. zonatus digestive system.