Strategies for the conservation and enhancement of Trissolcus japonicus (Ashmead), a parasitoid of the invasive Halyomorpha halys

In North America, Halyomorpha halys is an invasive pest of agricultural crops, ornamentals, and human-made structures. In its native range, H. halys populations are suppressed primarily by parasitoid wasps that attack the egg stage. Several species of parasitoid wasps, Trissolcus spp. (Hymenoptera: Schelionidae), are reported to attack H. halys eggs; however, those native to Utah have demonstrated only modest suppression of H. halys to-date. Trissolcus japonicus (Ashmead) has been identified as a key biocontrol agent and adventive populations were first detected attacking H. halys egg masses in northern Utah in 2019, and again in 2020 in the same and expanded locations. We have documented higher H. halys egg parasitism rates and lower trap catches in urban areas in the two years since T. japonicus was detected. According to ecological models, Utah is marginally suitable for T. japonicus and poses unique challenges to establishment due to its extreme climate and high elevation. Conservation efforts such as deploying H. halys kairomones identified as attractive to T. japonicus may enhance this wasp’s suppression of H. halys in agricultural settings. Custom grey rubber septa lures of n-tridecane and (E)-2-decenal at 4:1, 9:1, and 1:0 ratios were placed adjacent to sentinel H. halys egg masses in field trials. H. halys egg masses were evaluated for incidence (presence or absence) and intensity (proportion of parasitized eggs) of parasitism. Results on lure efficacy are presented.