Article
Forestry
Kelly M. McDonald, John R. Seiler, Bingxue Wang, Scott M. Salom, Rusty J. Rhea
Summary: The introduction of hemlock woolly adelgid has caused widespread mortality in eastern hemlock forests in the United States, threatening millions of hectares of these forests. The adelgid feeds on needles and reduces leaf-level physiology, leading to tree decline. This study investigated the leaf physiology of hemlocks at three forested sites with varying degrees of infestation. Treatment with imidacloprid, a commonly used control for adelgid, resulted in increased photosynthetic rates and stomatal conductance after one growing season. After two years, imidacloprid treatment also increased bud break and chlorophyll fluorescence. These findings suggest that adelgid-induced tree mortality is primarily due to reduced leaf area caused by decreased bud break, as well as a slight reduction in leaf-level photosynthesis and stomatal conductance.
Article
Biotechnology & Applied Microbiology
Albert E. Mayfield Iii, Tonya D. Bittner, Nicholas J. Dietschler, Joseph S. Elkinton, Nathan P. Havill, Melody A. Keena, David L. Mausel, James R. Rhea, Scott M. Salom, Mark C. Whitmore
Summary: The hemlock woolly adelgid (HWA) is an invasive insect that poses a threat to the ecological function of eastern hemlock and Carolina hemlock in eastern North American forests. Efforts to control HWA through the introduction of predator insects from Asia and western North America have had limited success. Recent research has focused on specific genetic lineages of parasitic flies that show promise for establishment in eastern North America.
BIOLOGICAL CONTROL
(2023)
Article
Entomology
Carrie S. Jubb, Thomas J. McAvoy, Kari E. Stanley, Ariel R. Heminger, Scott M. Salom
Summary: The study demonstrated that Laricobius nigrinus successfully established at 82% of release sites in Virginia and was the primary species recovered. While stand-level HWA densities varied greatly over sites and years, they showed a general decline over the course of the study.
Article
Biotechnology & Applied Microbiology
Hannah M. Thompson, Gregory Wiggins, Suzanne Lenhart
Summary: This study constructs a model to examine the joint impact of the invasive insect pest hemlock woolly adelgid and two introduced predator species on hemlock populations. The results show that the presence of predators can reduce adelgid densities and that the model allows for predator coexistence in natural settings.
BIOLOGICAL CONTROL
(2022)
Article
Biodiversity Conservation
Bruna R. Amaral, Andrew M. Wilson, Julie Blum, David A. Miller
Summary: Eastern hemlock forests in eastern North America are threatened by the invasive hemlock woolly adelgid. Although the negative effects of adelgid invasion on local bird communities have been documented, its regional impacts have not been quantified. This study used spatial and temporal databases to estimate the effects of adelgid infestation on bird species' demographic trends, and found significant declines in abundance for hemlock-associated bird species after infestation. However, these declines were not as universal at a broad spatiotemporal scale compared to local studies, suggesting that spatial heterogeneity may buffer them.
BIOLOGICAL INVASIONS
(2023)
Article
Ecology
Hannah M. Thompson, Thomas J. McAvoy, Gregory Wiggins, Scott M. Salom, Suzanne Lenhart
Summary: The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive insect pest that causes significant changes to hemlock forests in the eastern United States. An infestation of A. tsugae often leads to the death of eastern hemlock (Tsuga canadensis) within years. A model composed of systems of ordinary differential equations with time-dependent parameters is used to investigate the mechanisms behind cycles in hemlock health and A. tsugae density.
Article
Entomology
Carrie E. Preston, Nicholas J. Dietschler, Mark C. Whitmore, Scott M. Salom
Summary: In eastern US forests, classical biological control has been used to manage the hemlock woolly adelgid. Specialist predator species, such as silver flies, may offer a solution for regulating the adelgid populations. This study documents the phenology of Leucotaraxis argenticollis in relation to the hemlock woolly adelgid in the eastern United States.
ENVIRONMENTAL ENTOMOLOGY
(2023)
Article
Forestry
Austin Thomas, David C. Tilotta, John Frampton, Robert M. Jetton
Summary: Fraser fir, a tree endemic to the Southern Appalachians, is threatened by the introduced balsam woolly adelgid. This study identifies foliar terpenoids associated with adelgid infestations and suggests their potential use as indicators for resistance in future breeding programs.
Article
Entomology
Meg Sanders, Renee Tardani, Alexandra Locher, Kathryn Geller, Charlyn G. Partridge
Summary: The study aimed to find an affordable and efficient trap for early monitoring of hemlock woolly adelgid (HWA). The researchers found that the modified motorized trap showed good results in capturing HWA. Overall, the number of traps, elevation, and distance to infested hemlocks affected the capture success rate.
JOURNAL OF ECONOMIC ENTOMOLOGY
(2023)
Article
Forestry
Mary Ann Fajvan, Randall S. Morin
Summary: Landscape-scale maps of tree species densities are important for ecosystem management, especially in the case of threatened forests. Hemlock, a dominant species in riparian forests, plays a crucial ecohydrological role in deciduous landscapes. The spread of the nonnative hemlock woolly adelgid has led to widespread hemlock decline and mortality, prompting the need for identifying and prioritizing areas for supplemental conifer planting.
JOURNAL OF FORESTRY
(2021)
Article
Forestry
Gina A. Davis, Laura Lowrey, Tom Eckberg, Jeffrey A. Hicke, Ekaterina Smirnova
Summary: This study investigates the infestation and effects of the Balsam woolly adelgid (BWA) on host trees in Idaho. The presence of BWA increased across most sites regardless of host species. BWA causes severe damage and mortality of true fir, impacting tree diameter growth and age. This assessment provides baseline data for further analysis of insect, host, stand, and environmental interactions.
JOURNAL OF FORESTRY
(2022)
Article
Biodiversity Conservation
Natalie M. Bekins, David R. Brown
Summary: Chemical treatments have a positive effect on individual hemlocks but do not significantly impact avian species. The health of hemlocks may need to decline to a certain threshold before avian species respond.
NORTHEASTERN NATURALIST
(2022)
Article
Entomology
Samita Limbu, Melody A. Keena, Nicholas Dietschler, Katharine O'Connor, Mark C. Whitmore
Summary: In this study, the impact of temperature on the development and survival of different stages of the Hemlock woolly adelgid generation was investigated. The results showed that temperature significantly affected the development and mortality of the adelgids. Optimum temperatures for development were identified, along with lower temperature thresholds for different instars. The findings provide valuable information for the development of an annual phenology model for Hemlock woolly adelgid.
ENVIRONMENTAL ENTOMOLOGY
(2022)
Article
Entomology
Samita Limbu, Melody A. Keena, Nicholas Dietschler, Katharine O'Connor, Mark C. Whitmore
Summary: This study investigated the impact of temperature on the estivation and postaestivation stages of the sistens generation of Hemlock woolly adelgid (Adelges tsugae). The findings revealed that temperature significantly influenced the development and survival of this generation, with the highest mortality rate occurring at the coolest temperature (8 degrees C). The optimum temperatures for development ranged between 17 and 22 degrees C for different instars, and the lower temperature threshold for second instar nymphs and preoviposition period was estimated to be 0 degrees C and 3-5 degrees C, respectively. Furthermore, the study found that estivating first-instar sistentes resumed development after 40-100 days at constant temperatures, and only required 105 degree-days for 50% of the individuals to molt.
ENVIRONMENTAL ENTOMOLOGY
(2022)
Article
Forestry
Michael J. Campbell, Justin P. Williams, Erin M. Berryman
Summary: This study compares three methods for mapping Balsam woolly adelgid in subalpine fir forests in northern Utah, and finds that a combination of spectral, terrain, and climate data can accurately determine the severity of infestation.