Simple Summary Trissolcus japonicus, an important natural enemy of brown marmorated stink bug in Asia, was first detected in the USA in 2014. To investigate when and where T. japonicus is found in the field, yellow sticky traps were deployed in the canopy of tree of heaven growing at the edge of small isolated patches, windbreaks, and woodlots in 2018 and 2019. In both years, captures occurred from May to September, with peaks in July and August. Captures of T. japonicus were recorded from all three habitats but were not consistently associated with a particular habit. In 2017 and 2018, T. japonicus captures were compared between tree of heaven paired with several other H. halys host trees growing at the woods edge, and in 2019, captures in tree of heaven, black walnut, and black locust growing in the same windbreaks were compared. Trissolcus japonicus and several native H. halys parasitoids were captured in all hosts, but there was not a consistent effect of host tree species on T. japonicus captures. These results can be used to inform and optimize future surveillance efforts for detecting T. japonicus as it continues to expand its range in the USA. Trissolcus japonicus, an important egg parasitoid of Halyomorpha halys in Asia, was first detected in the USA in 2014. To evaluate the effect of habitat and the seasonality of T. japonicus detections in the USA, yellow sticky traps were placed in the canopy of Ailanthus altissima growing at the edge of isolated patches of trees, windbreaks, and woodlots in northern Virginia in 2018 and 2019. In both years, captures occurred from May to September, and peaked in July and August. While T. japonicus was detected in all habitats, there was not a consistent effect of habitat type on capture frequency. To evaluate tree species effects on T. japonicus captures, in 2017 and 2018, yellow sticky traps deployed in the canopy of A. altissima bordering apple orchards were paired with a nearby trap in one of several wild tree species along a common woods edge. In 2019, these traps were deployed in A. altissima, black walnut, and black locust growing in the same windbreaks. No consistent association between captures of T. japonicus or native parasitoids of H. halys and the tree species sampled was observed among years. Results are discussed in relation to the ecology and sampling optimization of T. japonicus.
