Laricobius nigrinus (Coleoptera: Derodontidae) Fender and Laricobius osakensis (Coleoptera: Derodontidae) Montgomery and Shiyake have been mass produced by Virginia Tech as biological control agents for the hemlock woolly adelgid (HWA), Adelges tsugae (Hemiptera: Adelgidae) Annand, for the past 15 and 9 yr, respectively. Herein, we describe modifications of our rearing procedures, trends and analyses in the overall production of these agents, and the redistribution of these agents for release to local and federal land managers. Based on these data, we have highlighted three major challenges to the rearing program: 1) high mortality during the subterranean portion of its life cycle (averaging 37% annually) reducing beetle production, 2) asynchrony in estivation emergence relative to the availability of their host HWA minimizing food availability, and 3) unintended field collections of Laricobius spp. larvae on HWA provided to lab-reared larvae complicating rearing procedures. We further highlight corresponding avenues of research aimed at addressing each of these challenges to further improve Laricobius spp. production.

Coleopteran species are biological control agents of numerous invasive pests.Laricobius nigrinus(Coleoptera: Derodontidae), a predaceous, univoltine species, spends the summer aestivating but is active for the rest of the year.Laricobius nigrinuspossesses many essential attributes for effective biological control of the hemlock woolly adelgid (Hemiptera: Adelgidae). The predator must be reared in large numbers for field releases. We describe some of the studies that led to the successful procedures currently used for mass rearingL. nigrinus.

Laricobius nigrinus Fender (Coleoptera: Derodontidae), a predatory beetle native to western North America, has been released since 2003 for management of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), a non-native pest killing hemlocks in eastern North America. Over 420,000 L. nigrinus have been released in the eastern USA from field and lab-reared sources, 14,000 of which were deployed in the Commonwealth of Virginia, USA. In order to determine the establishment rates of L. nigrinus in Virginia, surveys were conducted in 2017 and 2018 at all release sites within this state. During the study, stand-level HWA densities were estimated, and hemlock tree health and predatorprey ratios were quantified. The identification of Laricobius spp. recoveries were made using microsatellite analysis. During the period of the study, L. nigrinus were found to have established at 82% of Virginia release sites and were the primary species recovered (80%). Both Laricobius rubidus (18%) and hybrids (2%) were also recovered. Stand-level HWA densities varied greatly over sites and years but showed a general decline in year two of the study. Establishment at such a high percentage of release sites suggests that the climate in Virginia is suitable for the predator and the insect is adaptable to the wide variety of site conditions where hemlocks typically grow.

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Hemlock 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)(2015)(2016)(2017)(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 opencage 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 mortality and predation) greater than 80% for at least one year. Larvae of Laricobius spp. were recovered at all sites during this study. Sequencing of the COI gene from recoveries in Phase One (2015 and 2016) indicated that 88% were L. nigrinus and 12% were L. rubidus LeConte. Microsatellite analysis performed during Phase Two (2017 and 2018) indicated that approximately 97% of larval recoveries were L. nigrinus, 2% were hybrids of L. nigrinus and L. rubidus, and 1% were L. rubidus. Results of this study suggest that L. nigrinus can significantly impact the HWA sistens generation ovisacs and continued investment in the use of this species as a biological control is recommended. hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). The first detection of HWA in eastern North America was in Richmond, VA where it likely arrived sometime prior to 1951 on nursery stock (Havill et al., 2006). Since its accidental introduction, HWA has spread throughout a significant portion of the native range of