Boyle, Sean M.2019-10-182019-10-182017http://udspace.udel.edu/handle/19716/24489Native to eastern Asia, the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a polyphagous invasive pest in North America and Europe. Since its initial discovery in Allentown, Pennsylvania in 1996, H. halys has spread to 44 states in the continental US, many of which have reported significant economic damages to agriculture. One promising management strategy for H. halys currently being investigated is classical biological control, or the introduction of natural enemies. Specifically, egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Platygastridae) is considered the primary candidate biocontrol agent for field release, making it the subject of rigorous laboratory host range testing. However, these laboratory host range evaluations are ecologically-constricted and only provide the physiological host range of T. japonicus. Additional factors influencing an egg parasitoid’s true host range, such as its reception of host-related semiochemicals, effects of its parental host species on host location, and habitat overlap between suitable host species have yet to be adequately studied. Therefore, experiments focusing on these vital aspects of T. japonicus host preference were conducted to formulate a more accurate prediction of the parasitoid’s host specificity and ecological host range. ☐ To investigate if T. japonicus shows preference for H. halys adult kairomones over those of a physiologically-suitable, native species’, we conducted behavioral assays exposing female parasitoids to various leaf surface substrates contaminated with the chemical footprints of gravid female H. halys or Podisus maculiventris. In all three leaf substrate treatments, Trissolcus japonicus displayed clear preferences for leaf surfaces contaminated by its coevolved host H. halys. Female parasitoids resided significantly longer on H. halys contaminated leaf surfaces than on leaf surfaces contaminated by P. maculiventris. These results indicate that T. japonicus may be able to determine the suitability of a potential host using host-related chemical cues it perceives in the environment. ☐ To address possible influences of parental host species on T. japonicus host specificity, separate parasitoid strains were established using H. halys and P. maculiventris eggs as hosts. Female T. japonicus from both strains were exposed to soybean (Glycine max) leaf surfaces contaminated by adult kairomones of either stink bug species. Also, females from each strain were subject to no-choice tests where they were exposed to either H. halys or P. maculiventris egg masses in large mesh cages. Lastly, to determine possible phenotypic plasticity of T. japonicus, each female used in the no-choice tests were weighed and their right hind tibiae were measured. Results from the behavioral assays suggest that T. japonicus exhibits some degree of host fidelity while searching for hosts. Females which emerged from P. maculiventris eggs resided for equal amounts of time on leaves contaminated with kairomones from either stink bug species. Differences in no-choice test performance were not found between the two strains, as parasitism rates and host suitability were determined to be dependent on exposed host species and not the parasitoid strain. T. japonicus which emerged from H. halys possessed longer right hind tibiae and weighed roughly twice as much as wasps which emerged from P. maculiventris. ☐ To determine potential spatiotemporal overlap between H. halys and P. maculiventris, pheromone traps for both species were placed in woodland, fragmented, and agricultural habitats in early and late spring in 2016 and 2017. For both years, woodland traps yielded significantly greater captures than the other two habitats. Significant differences in woodland trap collections between the two species were observed in 2016, yet these differences were not found in 2017. Our trapping data suggest that these two species inhabit similar habitats during their spring activity. All together, our three studies expand on current host range testing protocols by providing novel methodologies for evaluating a biological control agent’s host specificity and its potential risks to non-target species.TrissolcusParasitoids -- Hosts -- ResearchBrown marmorated stink bug -- Control -- ResearchThesis10371512062018-02-22en