Establishment in an Introduced Range: Dispersal Capacity and Winter Survival of Trissolcus japonicus, an Adventive Egg Parasitoid.

The herbivorous brown marmorated stink bug, Halyomorpha halys, has spread globally, and one of its key parasitoids, Trissolcus japonicus, has recently been detected in the pest's introduced range. For an exotic natural enemy to impact its targeted host in a novel environment, it must disperse, locate hosts, and potentially be redistributed to susceptible sites. Through intentionally releasing T. japonicus across four Oregon eco-regions, we investigated an introduced parasitoid's dispersal capacity in urban sites and in two perennial crops, hazelnut and raspberry. In a second paired field and laboratory study, we investigated T. japonicus survival in different plant materials. Within three days of release, adult T. japonicus located host egg masses at 45% of sites and, one year later, were detected at 40% of release sites. Areas where released wasps survived winter were mostly urban or semi-natural. In commercial crop release experiments, we recovered the highest percentage of wasps in raspberry within 5 m of the release site but found no statistical difference in dispersal distance with some wasps dispersing up to 50 m. Adult parasitoids survived up to 16 weeks outdoors in the winter, with greater survival over time in bark compared to leaf litter. Wasp survival remained above 50% over the course of a simulated winter environment without precipitation. Our work affirms the continuation of H. halys parasitism by T. japonicus in novel environments and provides insight into the high population sizes necessary to survive winter and locate host egg masses the following season.

Spatial Associations of Vines Infected With Grapevine Red Blotch Virus in Oregon Vineyards.

Spread and in-field spatial patterns of vines infected with grapevine red blotch virus (GRBV) were documented in Oregon vineyards using field sampling, molecular diagnostics, and spatial analysis. Grapevine petiole tissue collected from 2013 to 2016 was tested using quantitative polymerase chain reaction for GRBV. At Jacksonville in southern Oregon, 3.1% of vines were infected with GRBV in 2014, and GRBV incidence reached 58.5% of study vines by 2016. GRBV-infected plants and GRBV-uninfected plants were spatially aggregated at this site in 2015, and infected plants were spatially associated between years 2015 and 2016. In a southern Oregon vineyard near Talent, 10.4% of vines were infected with GRBV in 2014, and infection increased annually to 21.5% in 2016. At Talent, distribution of the infected vines was spatially associated across all years. GRBV infection was highest at Yamhill, in the Willamette Valley, where 31.7% of the tested vines had GRBV infection in 2014. By 2016, 59.2% of the vines tested positive for GRBV. Areas of aggregation increased and were spatially associated across all years. From 2013 to 2015, GRBV was not detected at Milton-Freewater in eastern Oregon. Spatial patterns of GRBV infection support evidence of spread by a mobile insect vector. GRBV is a significant threat to Oregon wine grape production because of its drastic year-over-year spread in affected vineyards.

Bacterial Endosymbionts of the Psyllid Cacopsylla pyricola (Hemiptera: Psyllidae) in the Pacific Northwestern United States.

Insects often have facultative associations with bacterial endosymbionts, which can alter the insects' susceptibility to parasitism, pathogens, plant defenses, and certain classes of insecticides. We collected pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), from pear orchards in Washington and Oregon, and surveyed them for the presence of bacterial endosymbionts. Adult psyllids were collected on multiple dates to allow us to assay specimens of both the summer ("summerform") and the overwintering ("winterform") morphotypes. Two endosymbionts, Arsenophonus and Phytoplasma pyri, were detected in psyllids of both morphotypes in both states. A separate survey revealed similar associations present in psyllids collected in 1987. Arsenophonus was present in 80-100% of psyllids in all growing regions. A slightly lower proportion of summerform than winterform psyllids harbored the bacterium. Arsenophonus was present in the bacteriomes and developing oocytes of most psyllids, indicating that this endosymbiont is transovarially transmitted. This bacterium was also observed in the salivary glands and midguts of some psyllids. Phytoplasma pyri was present in a greater proportion of pear psylla from orchards near Yakima, WA, than from other regions, and was present in a higher proportion of winterforms than summerforms. We did not detect Wolbachia, Profftella, or Liberibacter europaeus, which are associated with other psyllid pests, including other species of Cacopsylla. Our study is the first to survey North American populations of C. pyricola for endosymbionts, and provides a foundation for further research on how bacterial associations may influence the ecology and management of this pest.