Range expansion of Trissolcus japonicus (Ashmead) in Utah and effects of floral resources on its prevalence

 Adventive populations of Trissolcus japonicus (Ashmead) have been detected in the United States since 2014 and were first detected in Utah in 2019. These populations may provide classical biological control for the invasive stink bug Halyomorpha halys (Stål) which can cause severe damage and economic loss, particularly to specialty crops in western North America.  Locations with adventive populations of T. japonicus across the United States are often in proximity to urbanized areas which can provide floral resources and overwintering shelter necessary for T. japonicus survival and establishment. To assess the range expansion of T. japonicus, sites throughout northern Utah were surveyed via yellow sticky cards May through September 2019-2021 in 14-day deployments. Results demonstrate the current range of T. japonicus in northern Utah and report factors affecting its presence.  In 2019 and 2020, T. japonicus was only recovered at highly urbanized sites, though this effect was not significant. In 2021, this effect was significant and 77% of captures fell within the highest urbanization category. Surveys conducted in 2021 were focused on 24 sites located at urbanized and rural orchard sites in northern Utah in order to examine the effect of three orchard groundcover types (bare soil, turf, and floral) on presence of T. japonicus. While T. japonicus was detected in orchards with all groundcover types, there was not a consistent effect of groundcover on presence. Results are discussed in relation to the establishment and biological control potential of T. japonicus in the Intermountain West.