Application of molecular techniques to track foraging and dispersal of a parasitoid wasp (Trissolcus japonicus)

Incorporating floral strips adjacent to crop blocks is a conservation biological control technique that attracts and retains natural enemies on farms, reducing pest pressure. In this study, we coupled this technique with the intentional release of a parasitoid wasp and hypothesized that wasps released directly into nectar-rich flowers would be more effective biological control agents in neighboring orchard blocks than wasps released into mowed grass. The parasitoid wasp we released was Trissolcus japonicus, a Scelionid from Asia that is naturalizing in the US that targets the invasive Brown marmorated stink bug, a major pest of tree fruit. We chose to sow buckwheat in the floral strip because lab studies show that T. japonicus survive well when provided with this flower. Before insect release, we applied a 10% egg white solution to the buckwheat so insects would become “marked” by the protein if they foraged.

We collected three types of data in this experiment: parasitism of stink bug egg masses, recapture of T. japonicus on sticky cards, and retention of the egg white protein marker. We utilized species-specific primers to run PCR and gel electrophoresis to confirm that recaptured insects were T. japonicus and not visually similar congenerics. Additionally, we ran enzyme-linked immunosorbent assays (ELISAs) to detect egg white antigens to determine if the same recaptured insects foraged in the buckwheat. By applying laboratory techniques to field dispersal studies, we can understand the movement pattern and foraging ecology of this important parasitoid and better employ ecologically informed agricultural management techniques.