Joshua M. Milnes, Nik G. Wiman, Elijah J. Talamas, Jay F. Brunner, Kim A. Hoelmer, Matthew L. Buffington, and Elizabeth H. Beers (2016) Discovery of an Exotic Egg Parasitoid of the Brown Marmorated Stink Bug, Halyomorpha halys (Stål) in the Pacific Northwest. Proceedings of the Entomological Society of Washington: Vol. 118, No. 3, pp. 466-470. doi: http://dx.doi.org/10.4289/0013-8797.118.3.466

Trissolcus japonicus (Ashmead), an Asian parasitoid of Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), was first detected in North America in 2014. Although testing in quarantine facilities as a candidate for classical biological control is ongoing, adventive populations have appeared in multiple sites in the United States, Canada, and Europe. Extensive laboratory testing of T. japonicus against other North American pentatomids and H. halys has revealed a higher rate of parasitism of H. halys, but not complete host specificity. However, laboratory tests are necessarily artificial, in which many host finding and acceptance cues may be circumvented. We offered sentinel egg masses of three native pentatomid (Hemiptera: Pentatomidae) pest species (Chinavia hilaris (Say), Euschistus conspersus Uhler, and Chlorochroa ligata (Say)) in a field paired-host assay in an area with a well-established adventive population of T. japonicus near Vancouver, WA. Overall, 67% of the H. halys egg masses were parasitized by T. japonicus during the 2-yr study. Despite the ‘worst case’ scenario for a field test (close proximity of the paired egg masses), the rate of parasitism (% eggs producing adult wasps) on all three native species was significantly less (0.4–8%) than that on H. halys eggs (77%). The levels of successful parasitism of T. japonicus of the three species are C. hilaris > E. conspersus > C. ligata. The potential impact of T. japonicus on these pentatomids is probably minimal.

Reliable monitoring of the invasive Halyomorpha halys abundance, phenology and geographic distribution is critical for its management. Halyomorpha halys adult and nymphal captures on clear sticky traps and in black pyramid traps were compared in 18 states across the Great Lakes, Mid-Atlantic, Southeast, Pacific Northwest and Western regions of the United States. Traps were baited with commercial lures containing the H. halys pheromone and synergist, and deployed at field sites bordering agricultural or urban locations with H. halys host plants. Nymphal and adult captures in pyramid traps were greater than those on sticky traps, but captures were positively correlated between the two trap types within each region and during the early-, mid- and late season across all sites. Sites were further classified as having a low, moderate or high relative H. halys density and again showed positive correlations between captures for the two trap types for nymphs and adults. Among regions, the greatest adult captures were recorded in the Southeast and Mid-Atlantic on pyramid and sticky traps, respectively, with lowest captures recorded in the West. Nymphal captures, while lower than adult captures, were greatest in the Southeast and lowest in the West. Nymphal and adult captures were, generally, greatest during July–August and September–October, respectively. Trapping data were compared with available phenological models showing comparable population peaks at most locations. Results demonstrated that sticky traps offer a simpler alternative to pyramid traps, but both can be reliable tools to monitor H. halys in different geographical locations with varying population densities throughout the season.

Three ‘Red Delicious,’ Malus domestica Borkhausen (Rosales: Rosaceae), apple plantings, each representing a different sport, were evaluated for natural resistance against the obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris). The establishment of neonate larvae on apple foliage was not different between the three ‘Red Delicious’ plantings. Of the three ‘Red Delicious’ plantings, the one that most negatively impacted OBLR was the ‘It Delicious’ genotype. The ‘It Delicious’ genotype at the Sunrise Research Orchard exhibited essentially 100% mortality against OBLR when fed on spring and summer foliage, and mortality accumulated faster across instars than on other ‘Red Delicious’ plantings. The high mortality observed in the ‘It Delicious’ genotype points to the existence of a putative gene, which we propose as Cro1. The other ‘Red Delicious’ plantings, Columbia River Orchard and Tree Fruit Research and Extension Center Research Orchard treatments, showed negative impacts, especially when exposed to foliage from the summer compared to the spring period. Development rates in these treatments in spring were higher compared to summer, and there were direct relationships between development rates, pupal weights, and adult longevity for both males and females. These latter results suggest that sublethal effects could be present in these ‘Red Delicious’ cultivars, thus offering insights to a gene-pyramiding strategy for breeders to managing leafroller pests in Washington apple.