Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): Melissa J. Fischer; Nathan P. Havill; Carlyle C. Brewster; Gina A. Davis; Scott M. Salom; Loke T. Kok
    Date: 2015
    Source: Biological Control. 82: 1-6.
    Publication Series: Scientific Journal (JRNL)
    Station: Northern Research Station
    PDF: Download Publication  (673.4 KB)


    Two adelgid predators, Laricobius nigrinus Fender and Laricobius rubidus LeConte, were recently discovered to produce hybrid progeny in the eastern United States. L. rubidus is native to eastern North America where it feeds on pine bark adelgid (Pineus strobi Hartig) and L. nigrinus is native to western North America and was introduced to the eastern United States in 2003 for biological control of hemlock woolly adelgid (Adelges tsugae Annand). Currently, L. nigrinus and L. rubidus form a mosaic of hybrid zones throughout the eastern United States. It is not known whether these zones will be maintained over time and whether hybridization will impact the efficacy of biological control or result in displacement of L. rubidus. Sampling from 2007 to 2012 on eastern hemlock (Tsuga canadensis Carrière) showed a clear increase in L. nigrinus, a decrease in L. rubidus, and a steady proportion of hybrids. Sampling from 2010 to 2012 on both eastern hemlock and white pine (Pinus strobus L.) at ten sites showed that L. nigrinus was more dominant on hemlock and L. rubidus was more dominant on white pine, which may demonstrate habitat preference and promote segregation between the two species. Site factors were tested for a relationship with the proportion of hybrids. The number of years L. nigrinus had been present at the site was the only factor that showed a relationship. The results suggest that L. nigrinus may displace L. rubidus on hemlock, but not on white pine at sites where they are both present.

    Publication Notes

    • Check the Northern Research Station web site to request a printed copy of this publication.
    • Our on-line publications are scanned and captured using Adobe Acrobat.
    • During the capture process some typographical errors may occur.
    • Please contact Sharon Hobrla, if you notice any errors which make this publication unusable.
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Fischer, Melissa J.; Havill, Nathan P.; Brewster, Carlyle C.; Davis, Gina A.; Salom, Scott M.; Kok, Loke T. 2015. Field assessment of hybridization between Laricobius nigrinus and L. rubidus, predators of Adelgidae. Biological Control. 82: 1-6.


    Google Scholar


    Hemlock woolly adelgid Laricobius nigrinus, Laricobius rubidus, Hybridization, Biological control

    Related Search

    XML: View XML
Show More
Show Fewer
Jump to Top of Page