Kairomone utilization in the host range evaluation of potential biological control agent Trissolcus japonicus (Hymenoptera: Scelionidae)

Authors: BOYLE, SEAN - University Of Delaware; Hoelmer, Kim; HOUGH-GOLDSTEIN, JUDITH - University Of Delaware

Submitted to: BARC Poster Day
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2017
Publication Date: 4/26/2017
Citation: Boyle, S.M., Hoelmer, K.A., Hough-Goldstein, J. 2017. Kairomone utilization in the host range evaluation of potential biological control agent Trissolcus japonicus (Hymenoptera: Scelionidae). BARC Poster Day.

Interpretive Summary: not required

Technical Abstract: The brown marmorated stink bug, Halyomorpha halys, is a highly polyphagous species native to Asia that has become a serious invasive agricultural and nuisance pest across North America. Its ability to feed on over 120 plant species, ranging from field crops and orchard fruit to ornamentals and native tree species, has facilitated its invasion as well as stymied the efficacy of common control methods (e.g. pesticide application). An alternative control method, such as “classical biological control” or the use of natural enemies, offers considerable potential in reducing numbers of H. halys. The solitary egg parasitoid Trissolcus japonicus has been identified as the primary candidate for release, yet in order to release the parasitoid its host range must be evaluated to determine possible non-target risks it may pose on native stink bug species. Standard laboratory host range testing for a potential biological control agent generally involves highly artificial conditions, and only reveals the agent’s “physiological” host range which tends to overestimate non-target effects. For this reason, novel host range assessments utilizing realistic ecological factors are needed to more accurately predict an agent’s true host range. Since the host range testing for T. japonicus included artificial conditions (i.e. stink bug eggs in a test tubepetri dish) and only measured parasitism rate and development of T. japonicus, our study focused on integrating response to host species’ contact kairomones (chemical footprints) and parasitoid behavioral observations to further evaluate the host preferences of T. japonicus. More specifically, we observed and measured T. japonicus’ host searching behaviors when exposed to plant surfaces contaminated by kairomones from its coevolved hosted, H. halys, or from a beneficial native stink bug host, Podisus maculiventris. These parasitoid host searching behaviors included: (1) residence time on the contaminated leaf surface, (2) linear walking speed, and (3) angular velocity (turning rate). Also, we used three different plant leaf substrates (Red maple, apple, and soybean) to evaluate possible effects of leaf surface type on the parasitoid’s host searching behaviors. Across all leaf surfaces treatments, Trissolcus japonicus resided significantly longer on H. halys contaminated leaves than on P. maculiventris contaminated leaves. In addition, T. japonicus walked significantly slower on red maple leaves contaminated by H. halys than on red maple leaves contaminated by P. maculiventris. These results suggest that T. japonicus will likely spend more time and energy in searching for a host within habitats that possess H. halys kairomones, and therefore will have a higher probability of locating and parasitizing H. halys eggs instead of native stink bug eggs. Overall, our study proposes that kairomone-based behavioral studies can be utilized to further evaluate the host specificity of a biological control agent and can be an invaluable supplement to classic host range testing regimes.