Impact of the biological control agent, Laricobius nigrinus, on hemlock woolly adelgid sistens generation and their ovisacs in the eastern United States

Publication date: Available online 23 December 2019Source: Biological ControlAuthor(s): Carrie S. Jubb, Ariel R. Heminger, Albert E. Mayfield III, Joseph S. Elkinton, Gregory J. Wiggins, Jerome F. Grant, Jeffrey A. Lombardo, Thomas J. McAvoy, Ryan S. Crandall, Scott M. SalomAbstractHemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), is an invasive pest causing significant mortality to eastern and Carolina hemlock in eastern North America. Since 2003, management of HWA has included targeted release of the HWA predator Laricobius nigrinus Fender (Coleoptera: Derodontidae), native to western North America. Establishment of L. nigrinus at release sites is well documented, but investigations of its impact on HWA populations have been limited. A four-year (2014-2018), two-phase study using predator exclusion cages to assess the impact of L. nigrinus on HWA was conducted at nine previous release sites in the eastern United States. Significantly more HWA sistens ovisacs were disturbed on no-cage and open-cage branches than on caged branches where predators were excluded. Mean disturbance levels on cage, no-cage and open-cage branches was 8, 38, and 27 percent, respectively. Seven of nine sites had a mean HWA ovisac disturbance greater than 50% for at least one year. Winter temperatures were also a significant factor in overall mortality of the sistens generation with a mean of 46% on study branches. Six of nine sites had a mean overall mortality (winter mortal...
Source: Biological Control - Category: Biology Source Type: research