Rebound of Adelges tsugae spring generation following predation on overwintering generation ovisacs by the introduced predator Laricobius nigrinus in the eastern United States

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dc.contributor.authorCrandall, Ryan S.en
dc.contributor.authorJubb, Carrie S.en
dc.contributor.authorMayfield, Albert E., IIIen
dc.contributor.authorThompson, Biffen
dc.contributor.authorMcAvoy, Thomas J.en
dc.contributor.authorSalom, Scott M.en
dc.contributor.authorElkinton, Joseph S.en
dc.contributor.departmentEntomologyen
dc.date.accessioned2021-03-17T13:08:15Zen
dc.date.available2021-03-17T13:08:15Zen
dc.date.issued2020-06en
dc.description.abstractHemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), has devastated eastern hemlock (Tsuga canadensis [L.] Carriere) in a major portion of its native range in eastern North America. Population dynamics of HWA in the absence of predators have been studied for decades. After many years and much effort directed towards rearing and releasing biological control agents to manage HWA, one of these agents, Laricobius nigrinus Fender (Coleoptera: Derodontidae), is now successfully established at significant densities at sites from the southern to the mid-Atlantic states of the eastern U.S. However, high densities of HWA still persist at many locations throughout the region and spread of HWA and associated damage to hemlock continues. Population models for HWA have suggested that even upwards of 90% predation on eggs laid by the overwintering sistens generation will have minimal effect in reducing the population densities of HWA, if HWA are at high density. In this study, we tested the ability of L. nigrinus to reduce HWA densities, and experimentally tested these model predictions to better understand what impact, if any, L. nigrinus has on HWA densities. By using predator exclusion cages at field sites with well-established populations of L. nigrinus, we were able to record HWA densities, fecundity, overwintering mortality, and predation by L. nigrinus, as well as the proportion of branch tips producing new growth on study trees. Using our field-collected data, we refitted the model in ways that allowed us to predict what population densities we could expect for the following summertime progrediens generation given previous HWA density and levels of L. nigrinus. In both years, we found that despite high rates (greater than 80% ovisac predation) of predation by L. nigrinus on uncaged branches compared to caged branches, there were no significant differences in subsequent densities of the HWA spring generation between caged and uncaged treatments, as predicted by our model. In 2018, our field-collected densities of the summer progrediens generation were lower than what was predicted by the model in both predator exclusion treatments, possibly due to the model not incorporating tree health and climatic factors. Simulation models of pest insect populations based on field-collected data such as fecundity, density, overwintering mortality, and predation, could prove to be important in informing researchers and managers about the role of the biological control agent in the population dynamics of the target host.en
dc.description.adminPublic domain – authored by a U.S. government employeeen
dc.description.notesThis work was funded by a cooperative agreement with the USDA Forest Service, USA (No. 14-CA-11420004-181). We thank R., Reardon, N. Schneeburger, R. Rhea of the Forest Service for arranging and administrating our funding, M. Meyer for helping us find field sites in NJ and R. Mays, A. Dechaine (Virginia Tech) and B. Mudder (USDA Forest Service) for helping collect samples from the field. We thank A. Roehrig, A. Langevin for processing samples. We thank H. Broadley, J. Anderson, and B. Padilla for help with statistical analysis and graphics. We thank J. Chandler, R. Van Driesche, and D. Orwig for reviewing earlier drafts of this MS.en
dc.description.sponsorshipUSDA Forest Service, USA [14-CA-11420004-181]en
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1016/j.biocontrol.2020.104264en
dc.identifier.eissn1090-2112en
dc.identifier.issn1049-9644en
dc.identifier.other104264en
dc.identifier.urihttp://hdl.handle.net/10919/102731en
dc.identifier.volume145en
dc.language.isoenen
dc.rightsPublic Domainen
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/en
dc.subjectAdelges tsugaeen
dc.subjectBiological controlen
dc.subjectLaricobius nigrinusen
dc.subjectPredatoren
dc.subjectTsuga canadensisen
dc.titleRebound of Adelges tsugae spring generation following predation on overwintering generation ovisacs by the introduced predator Laricobius nigrinus in the eastern United Statesen
dc.title.serialBiological Controlen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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