Cold tolerance of Trissolcus japonicus (Hymenoptera: Platygastridae), an egg parasitoid of brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae)

Halyomorpha halys Stål, the brown marmorated stink bug, is an invasive species that was first detected in the United States in Pennsylvania in 1996. In Minnesota, H. halys was first detected in 2010, with evidence supporting the presence of a reproductive population following in 2013. H. halys is polyphagous and a pest of economic concern.  Additionally, it can be a nuisance pest as a household invader during winter. Because H. halys has few natural enemies in the United States, a group of parasitic wasps have been evaluated as potential classical biological control agents. One species, Trissolcus japonicus Ashmead, shows promise due to the short life span (2-3 weeks), multiple generations per season, and parasitism rates of 60-80% in the native range. One vital step in determining their potential efficacy in Minnesota is to first assess their capability to withstand winter temperatures. We began by gathering cold tolerance measurements (i.e., supercooling point and lower lethal temperature) of unacclimated T. japonicus from four geographically distinct areas in East Asia: Beijing, China; Nanjing, China; Puncheon, South Korea; and Tsukuba, Japan. We will compare measures of cold tolerance among the populations. Preliminarily, the mean unacclimated supercooling point of T. japonicus was -21.8 °C, which is below the mean Minnesota winter temperature range of -14.4 to -18.9 °C. Future work is needed to evaluate cold acclimated populations of T. japonicus.