COMMUNITY AND ECOSYSTEM ECOLOGY Parasitoids Reared From Predators of Hemlock Woolly Adelgid (Hemiptera: Adelgidae), and the Hymenopterous Parasitoid Community on Western Hemlock in the Pacific Northwest

In western North America, infestations of the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), are common on orchard, ornamental, and roadside western hemlock, Tsuga heterophylla (Raf.) Sargent. However, these infestations rarely cause T. heterophylla mortality.Host tolerance andpresence of endemic predatorsmaybe contributing to the relatively low levels of injury to T. heterophylla caused by A. tsugae. Field surveys of the arthropod community associatedwithA. tsugae infestations on 116 T. heterophylla at 16 sites inOregon andWashingtonwere conducted every 4Ð6 wk from January 2005 through November 2006. Fourteen uninfested T. heterophylla were also surveyed across 5 of the 16 sites. Immature A. tsugae predators collected in the Þeld were brought to the laboratory for rearing. Eight species of hymenopterous parasitoids were reared from pupae of predators of A. tsugae in the laboratory. Two Pachyneuron spp. (Pteromalidae) and a Melanips sp. (Figitidae) were reared from Leucopis spp. (Diptera: Chamaemyiidae) puparia. Syrphoctonus pallipes (Gravenhorst) (Ichneumonidae), Woldstedtius flavolineatus (Gravenhorst) (Ichneumonidae), Syrphophagus sp. (Encyrtidae), andPachyneuron albutiusWalkerwere reared from Syrphidae (Diptera) puparia. A Helorus sp. (Heloridae) was reared from a Chrysoperla sp. (Neuroptera: Chrysopidae) cocoon. Laboratory rearing did not show any direct association between parasitoids and A. tsugae. In the Þeld survey, a total of 509 adult parasitic Hymenoptera representing 19 families and at least 57 genera were collected from T. heterophylla. Nonparametric analysis of community structure showed Pachyneuron spp. were strongly correlated to abundance of their Leucopis spp. hosts and to A. tsugae population score in the Þeld. The possible impact of parasitism on Leucopis spp., potential A. tsugae biological control candidates for the eastern United States, is discussed.