The Discovery of Trissolcus japonicus (Hymenoptera: Scelionidae) in Michigan

The invasive brown marmorated stink bug, Halyomorpha halys (Stål), is a pest of growing economic importance in the United States, the control of which currently relies on pesticide applications. Biological control could provide sustainable and long-term control but classical biological control agents have not yet been approved. Adventive populations of a potential biological control agents, the Samurai wasp, Trissolcus japonicus (Ashmead), have been found in the United States, first in Maryland in 2014, expanding its range west to Ohio by 2017. Trissolcus japonicus is a highly effective parasitoid of H. halys eggs, but its redistribution and augmentative releases are restricted to states where it has been detected in the wild. To assess the presence of T. japonicus in Michigan and attack rates of H. halys by native natural enemies we deployed 189 H. halys egg masses at ten sites in lower Michigan between May and October in 2018. In addition, we deployed 51 native stink bug egg masses at the same sites to evaluate potential non-target effects of T. japonicus in the field, which were shown to occur in laboratory studies. We found T. japonicus in a single H. halys egg mass, which constitutes the first record of this Asian parasitoid in Michigan. Native predators and parasitoids caused minimal mortality of H. halys eggs and we did not find evidence of non-target effects of T. japonicus on native stink bug species. These findings open the door to initiation of a classical biological control program using an efficient, coevolved parasitoid from the native range of H. halys

Arthropod community organization and development in pear

Arthropod communities in pear are conceptualized as hierarchically organized systems in which several levels of organization or subsystems can be recognized between the species population level and the community as a whole. An individual tree is taken to be the community habitat with arthropod subcommunities developing on leaf, fruit and wood subcommunity habitats. Over a hundred species are reported to colonize one or more subcommunity habitats. Each subcommunity is composed of trophically organized systems of populations. Each system of populations is comprised of a guild of arthropods that use the habitat primarily for feeding but also for overwintering or egg deposition, and associated guilds of specialized predators, parasitoids and hyperparasitoids. Understanding community organization entails understanding how subsystems and their environments interact so as to be incorporated into a unified whole. Along with the relatively specialized interrelationships so important in organizing systems of populations, higher level community subsystems are coupled through the activities of phytophagous and predaceous generalists which feed in or take their prey from more than one subcommunity. In meeting the habitat requirements of each of its life history stages, several members of the pear community move from one subcommunity to another during the course of community development and serve to integrate these subsystems. Additional habitat, trophic and life history aspects of subsystem incorporation and interpenetration are discussed. Community development or change in organization through time is conceptualized as being jointly determined by the development of the habitat and the organization of the species pool. Seasonal development of the pear arthropod community is described in terms of changes in the species composition, size, and spatial distribution of guilds and subcommunities. Community habitat development is taken to be the primary determinant of changes in community structure and organization. As the season progresses, changes in the kinds and biomass of developmental states of each subcommunity habitat are accompanied by changes in the kinds, number or biomass, and distribution of associated community subsystems. Although the influence of habitat development on community development is emphasized, it is from the the species pool that arthropods colonize pear. The species that colonize, and their abundance and time of arrival is partially determined by the organization of this system of communities

The Discovery of Trissolcus japonicus (Hymenoptera: Scelionidae) in Michigan

The invasive brown marmorated stink bug, Halyomorpha halys (Stål), is a pest of growing economic importance in the United States, the control of which currently relies on pesticide applications. Biological control could provide sustainable and long-term control but classical biological control agents have not yet been approved. Adventive populations of a potential biological control agents, the Samurai wasp, Trissolcus japonicus (Ashmead), have been found in the United States, first in Maryland in 2014, expanding its range west to Ohio by 2017. Trissolcus japonicus is a highly effective parasitoid of H. halys eggs, but its redistribution and augmentative releases are restricted to states where it has been detected in the wild. To assess the presence of T. japonicus in Michigan and attack rates of H. halys by native natural enemies we deployed 189 H. halys egg masses at ten sites in lower Michigan between May and October in 2018. In addition, we deployed 51 native stink bug egg masses at the same sites to evaluate potential non-target effects of T. japonicus in the field, which were shown to occur in laboratory studies. We found T. japonicus in a single H. halys egg mass, which constitutes the first record of this Asian parasitoid in Michigan. Native predators and parasitoids caused minimal mortality of H. halys eggs and we did not find evidence of non-target effects of T. japonicus on native stink bug species. These findings open the door to initiation of a classical biological control program using an efficient, coevolved parasitoid from the native range of H. halys