Field surveys for native Minnesota stink bugs and dynamic host acceptance in the stink bug egg parasitoid, Trissolcus japonicus

The samurai wasp, Trissolcus japonicus is a parasitoid of the invasive brown marmorated stink bug, Halyomorpha halys. Though H. halys is a preferred host, T. japonicus can complete development on many native North American stink bugs. Trissolcus japonicus was recently detected in Minnesota, prompting surveys of the parasitoid, H. halys, and native stink bugs in the state in 2024 and 2025. These surveys found 12 native stink bug species, several of which have shown low-to-moderate susceptibility for parasitism by T. japonicus in laboratory tests or have not yet been screened in previous studies. Though previous host range tests provide insight into the risk posed by this parasitoid to native species, many do not account for environmental or biological stressors that could impact T. japonicus host choice. For parasitoid wasps, egg-laying females must carefully manage somatic maintenance and egg production. This manifests as a balancing act of nutrient and egg limitation, such that a parasitoid may be more likely to accept non-preferred hosts when egg loads are high and/or food availability is low. To determine the impact of nutrient and egg limitation on T. japonicus host-choice, naive female wasps were either starved or provided sugar-water, and kept at low or high temperatures to manipulate egg load. These parasitoids were exposed to egg masses of H. halys, a preferred host, or Euschistus variolarius, a less-preferred native host. This experiment improves our understanding of the conditions under which T. japonicus may pose a greater risk to native stink bug species.