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Dissertations / Theses on the topic 'Eastern hemlock'

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Published: 4 June 2021

Last updated: 30 July 2024

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1

Walker, David Matthew. "Radial growth response of eastern hemlock to infestation of hemlock woolly adelgid." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/31920.

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Hemlock woolly adelgid (Adelges tsugae Annand) is causing defoliation and mortality of eastern hemlock (Tsuga canadensis (L.) CarriÃ¨re) in the eastern United States. The objectives of this study were to quantify changes in tree-ring width and wood anatomy for trees that survived adelgid infestation, and to contrast dendroclimatic relationships across a latitudinal gradient. Six sites spanning the current range of hemlock woolly adelgid (HWA) infestation were selected. At each site, 23 infested eastern hemlocks were cored and two trees were felled at the Virginia site and thin-sectioned using a sliding microtome for analysis of wood anatomy. Tree cores were cross-dated and ring widths were measured. For each site, t-tests were used to determine if there was a difference in radial growth pre- and post-HWA arrival. To compare differences in pre- and post-HWA cell properties, t-tests were used. For dendroclimatic analysis, Pearson correlation coefficients were calculated between radial growth and monthly climate variables. Three sites showed significant suppression in radial growth after HWA arrival and latewood produced post- HWA arrival had significantly smaller cells with reduced cell-wall thickness than latewood produced before HWA arrival. This indicates that HWA can reduce a treeâ s photosynthate production. The relationship between hemlock growth and climate also varied with latitude and site, with trees growing further south or on shallower soils being more sensitive to moisture levels. This sensitivity to drought can also partially explain the variation in hemlock response to adelgid feeding, as trees affected by moisture stress tend to be more sensitive to insect attack.
Master of Science

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2

DeMaio, Sophia. "Using Dendrochronology to Understand the Response of Eastern Hemlock to Past Stresses and its Current Status in Southern Maine." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/DeMaioS2008.pdf.

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3

Ayars, Alicia T. "Detecting hemlock woolly adelgid (Adeleges tsugae) impacts on eastern hemlock (Tsuga canadensis) stands in the Quabbin Reservoir Watershed using AIMS-1 imagery /." Connect to online version, 2005. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2005/118.pdf.

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4

Jones, Jonathan. "Determination of imidacloprid by ELISA and GC/MS a comparison of analytical techniques and a coordinated field study with the U.S. Forest Service to determine uptake and persistence in imidacloprid treated hemlock tress /." Click here for download, 2007. http://proquest.umi.com/pqdweb?did=1288664741&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.

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5

McDonald, Kelly Marie. "Eastern Hemlock Needle Physiology as Impacted by Hemlock Wooly Adelgid and Treatment with Imidacloprid." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/24196.

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Eastern hemlock (Tsuga canadensis [L.] Carr.) is a foundation species that occupies a unique niche in forest ecosystems and which often forms pure stands throughout the eastern United States. Throughout the last half of a century, widespread mortality of T. canadensis had been occurring with the introduction of the invasive pest, hemlock woolly adelgid (Adelges tsugae Annand) (HWA). HWA now threatens to destroy millions of hectares of hemlock dominated forests and to disrupt its associated ecosystems. In order to determine how HWA impacts hemlock physiology, three sites with various degrees of infestation were chosen and half of the trees at each site were treated with imidacloprid (Merit® 2 F, Bayer, Kansas City, MO) while the rest were left untreated. Needle gas exchange was assessed monthly using a LI-COR 6400 portable open path gas exchange system (LI-COR Inc, Lincoln NE). Chlorophyll fluorescence and bud break were also characterized for all trees at two of the three sites. After one complete growing season, we found a slight increase in photosynthetic rates (4.98 %), increased bud break at Fishburn (562 %) and Mountain Lake (25.6 %) sites, and no change in chlorophyll fluorescence for imidacloprid treated trees. These results suggest that HWA is causing tree mortality largely through a reduction of leaf area and not a reduction in leaf level photosynthetic capacity. By quantifying the physiological response of T. canadensis to HWA, better insights can be made into understanding tree decline as it relates to HWA.
Master of Science

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6

Clark, Joshua Taylor. "DISTRIBUTION OF EASTERN HEMLOCK, TSUGA CANADENSIS, IN EASTERN KENTUCKY AND THE SUSCEPTIBILITY TO INVASION BY THE HEMLOCK WOOLLY ADELGID, ADELGES TSUGAE." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/1.

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The hemlock woolly adelgid, an invasive non-native insect, is threatening eastern hemlock in Kentucky. This study examined three techniques to map the distribution of eastern hemlock using decision trees, remote sensing, and species distribution modeling. Accuracy assessments showed that eastern hemlock was best modeled using a decision tree without incorporating satellite radiance. Using the distribution from the optimal model, risk maps for susceptibility to hemlock woolly adelgid infestation were created using two species distribution models. Environmental variables related to dispersal were used to build the models and their contributions to the models assessed. The models showed similar spatial distributions of eastern hemlock at high risk of infestation.

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7

Iosue, Francis V. "The role of phytochemicals and leaf cushion morphology in host resistance to the hemlock woolly adelgid (Adelges tsugae)." Click here for download, 2008. http://proquest.umi.com/pqdweb?did=1495963831&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.

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8

F, Snider Scott. "Predicting infestations of hemlock woolly adelgid (Adelges tsugae) in Great Smoky Mountains National Park, Tennessee/North Carolina, USA." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1103233070.

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9

Knisley, Jordan K. "Eastern Hemlock (Tsuga canadensis) Forests of the Hocking Hills Prior to Hemlock Woolly Adelgid (Adelges tsugae) Infestation." Ohio University Honors Tutorial College / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1617969072642887.

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10

Macy, Thomas Daniel. "Current composition and structure of eastern hemlock ecosystems of northeastern Ohio and implications of hemlock woolly adelgid infestation." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337968205.

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11

Daniel, Nathan A. "American Chestnut Restoration in Eastern Hemlock-Dominated Forests of Southeast Ohio." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1323993012.

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12

Jones, Anne. "Fitness and Physiology of the Hemlock Woolly Adelgid, Adelges tsugae, in Relation to the Health of the Eastern Hemlock, Tsuga canadensis." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/53700.

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The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Sternorrhyncha: Adelgidae) is a small invasive insect that frequently causes hemlock (Tsugae spp.) mortality in the eastern United States. Studies have shown that once healthy hemlocks become infested by the adelgid, nutrients are depleted from the tree, leading to both tree decline and a reduction of the adelgid population. Since A. tsugae is dependent on hemlock for nutrients, feeding on trees in poor health may affect the insect's ability to obtain necessary nutrients and consequently affect their population and physiological health. A cluster analysis, based on quantitative and qualitative tree health measurements, grouped sample trees into categories of lightly and moderately impacted trees. The A. tsugae population health on each tree was determined by measuring insect density, survival from aestivation, and peak fecundity. A. tsugae physiological health was determined similarly by measuring insect biomass, total carbon, carbohydrate, total nitrogen, and amino nitrogen. A. tsugae from moderately impacted trees exhibited significantly greater fecundity; however, A. tsugae from lightly impacted hemlocks contained significantly greater levels of carbohydrates, total nitrogen, and amino nitrogen. All A. tsugae physiological parameters increased significantly over time as the insects matured and reproduced regardless of tree health classification. While the results of the physiological analysis generally support our hypothesis that A. tsugae on lightly impacted trees are healthier than those on moderately impacted trees, this was not reflected in the population fitness measurements of the insects. Further examination of A. tsugae egg health may elucidate this apparent contradiction.
Master of Science in Life Sciences

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13

Lemieux, Michée. "Cytoplasmic DNA polymorphisms in eastern hemlock: Genogeographic analyses and implications for gene conservation." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27408/27408.pdf.

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14

Lemieux, Michée Joseph. "Cytoplasmic DNA polymorphisms in eastern hemlock : genogeographic analyses and implications for gene conservation." Master's thesis, Université Laval, 2010. http://hdl.handle.net/20.500.11794/21903.

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Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2010-2011
La distribution géographique actuelle de la pruche de l'est (Tsuga canadensis L.) se situe au sud-est du Canada et longe les Appalaches aux États-Unis. Des efforts de développement de marqueurs d'ADN cytoplasmique ont été entrepris dans cette étude afin de vérifier si la diversité génétique de l'espèce était uniforme ou structurée, une information pertinente pour guider les efforts de conservation. Parmi sa distribution, soixante populations (n = 892) ont été échantillonnées. Aucun polymorphisme d'ADN mitochondrial n'a été détecté alors que sept marqueurs d'ADN chloroplastique se sont révélés polymorphes. La différenciation de populations était faible (GST = 0,020), possiblement en raison de l'homogénéisation par le flux pollinique durant l'Holocène. Néanmoins, des analyses spatiales ont décelé une structure significative entre l'est et l'ouest des Appalaches. On retrouve une plus grande différenciation de populations ainsi qu'une plus forte richesse allélique au sud-est des Appalaches, ce qui confère à cette région une priorité de conservation ex situ.

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15

Johnson, Marie. "Demography and dendrochronology of a disjunct population of eastern hemlock in Southwestern Ohio." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1535073403943795.

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16

Klunk, Wess M. "Sasajiscymnus tsugae (Coleoptera: Coccinellidae) as a biological control for Hemlock Woolly Adelgid (Adelges tsugae (Hemiptera: Adelgidae)) on Eastern Hemlock, (Tsugae canadensis) and Carolina Hemlock (T. caroliniana) in western North Carolina, USA." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193080475/.

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17

Beane, Nathan R. "Stand dynamics of an old-growth hemlock-hardwood forest in West Virginia." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5442.

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Thesis (M.S.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains vii, 55 p. : ill., maps. Includes abstract. Includes bibliographical references (p. 47-50).

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18

Huggett, Brett Andrew. "The Plant Vascular System: Structure, Function, and Responses to Environmental Stress." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10913.

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Environmental stressors such as nutrient deficiency and insect infestation can significantly impact tree health. Despite much research on the ecological effect on forests in the northeastern United States due to calcium depletion and hemlock woolly adelgid infestation, little is known regarding the physiological mechanisms altered by these stress factors. I tested the hypothesis that calcium depletion, associated with sugar maple decline, compromises water transport processes as a result of calcium-related reductions in cell growth and stabilization. A survey of forest-grown sugar maples from a long-term replicated calcium-manipulation study showed no significant impact of calcium deficiency on wood density, stem hydraulic conductivity (Ks), or vulnerability to cavitation (VC). In vitro removal of xylem-bound calcium showed no impact on VC or air seeding thresholds (Pt). Results suggest that sugar maple decline is not caused by compromises in xylem function due to calcium deficiency. I also tested the hypothesis that hemlock woolly adelgid (Adelges tsugae Annand) (HWA) infestations impact water transport processes and nutrient partitioning in eastern hemlock trees. HWA infestation resulted in higher Ks due to an increase in average tracheid lumen area associated with the proliferation of false rings. HWA-infested trees exhibited higher rates of net photosynthesis and significant changes in foliar nutrient partitioning. These results are the first to demonstrate increases in Ks and alterations in foliar cation levels in response to HWA infestation. In two additional studies, I investigated methods for evaluating the structure and function of xylem networks. Using sequential sectioning of aerial roots of epiphytic aroids, I directly quantified the topographic relation of vessels in a single organ with measurements of vessel length, diameter, vessel end overlap length, and vessel stelar orientation. In a separate study, I explored the relationship between vessel length and measurements of Pt. In establishing guidelines for estimating whole-stem cavitation with the use of single vessel air injection, I demonstrate that calculations of Pt are influenced by stem length measured and removal of native emboli prior to testing. Improvements in tools to quantify xylem structure and function will enhance our ability to understand the responses of forest trees to environmental stress.

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19

Gerschutz, Andrew Daniel Peet R. K. "Changes in old-growth and second-growth eastern hemlock Tsuga canadensis communities in the southern Appalachians after the introduction of the hemlock woolly adelgid, Adelges tsugae." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2779.

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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2009.
Title from electronic title page (viewed Mar. 10, 2010). "... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Biology." Discipline: Biology; Department/School: Biology.

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20

Hervieux, Meggy. "Factors affecting defoliation of eastern hemlock (Tsuga canadensis) by the pale-winged gray moth (Iridopsis ephyraria)." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106455.

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The main objective of this thesis was to study the possible factors that could explain the feeding preference of the pale-winged gray moth (PWG) (Iridopsis ephyraria) for the mid-lower crown of eastern hemlocks in south-west Nova Scotia. I first described egg and larval distribution between crown locations of mature hemlocks. I then focused on testing two hypotheses that could explain the pale-winged gray feeding preference for the foliage located in the mid-lower crown: (1) hygrothermal and (2) foliage quality hypotheses. My research shows that eggs and larvae were principally located in the mid-lower crown. This larval preference could partly explain the greatest defoliation in the mid-lower crown of mature hemlocks. Experimental and observational data revealed that both hygrothermal stress and foliage quality varied between crown locations and thus affected the PWG feeding preference. The disadvantages of heat and water stress in the upper crown, however, outweighed the benefits to feed on higher foliage quality which explains the PWG feeding preference for foliage in the mid-lower crown. Additional data on foliage age showed that larvae prefer to feed on current-year foliage presumably because this age-class had higher water and nitrogen content. This feeding preference may have helped larvae to survive in the upper crown where temperatures are warmer. This research adds to the literature on plant-insect interactions, allows a better understanding of the pale-winged gray moth natural history but mostly, informs us on the factors that affect PWG survival.
Récemment, la région sud-ouest de la Nouvelle-Écosse a été sévèrement touchée par l'arpenteuse à tâches (Iridopsis ephyraria), un lépidoptère s'attaquant principalement à la Pruche du Canada (Tsuga canadensis). L'objectif principal de ce mémoire était d'explorer les facteurs pouvant expliquer la préférence alimentaire de l'arpenteuse à tâches pour le feuillage retrouvé dans la couronne inférieure des pruches du Canada. En premier lieu, j'ai décrit la distribution des oeufs et des larves de l'arpenteuse à tâches entre les différentes strates des pruches matures. J'ai ensuite vérifié différentes hypothèses pouvant expliquer la distribution verticale de l'espèce dans la canopée : (1) la variation du microclimat (i.e. température et humidité) ainsi que (2) les changements dans la qualité du feuillage. Les oeufs et les larves de l'espèce étaient principalement localisés dans la partie inférieure de la canopée. La défoliation plus importante au niveau de la couronne inférieure des arbres matures pourrait, en partie, être expliquée par cette préférence chez les larves. Dans le chapitre 3, mes résultats ont démontré que le stress hydrique (stress causé par une température élevée et un faible taux d'humidité) ainsi que la qualité du feuillage ont influencé la préférence alimentaire de l'arpenteuse à tâches. Toutefois, les effets négatifs du stress hydrique ont davantage influencé la distribution finale de l'espèce dans les pruches du Canada comparativement aux effets reliés à la qualité du feuillage. De plus, mes données ont révélé que l'arpenteuse à tâches préfère se nourrir sur le feuillage de l'année courante qui comporte plus d'eau et d'azote. Cette préférence pour le feuillage de l'année courante pourrait favoriser la survie des larves retrouvées dans le haut de la canopée où le stress hydrique est supérieur. Ce projet a permis d'ajouter à la littérature scientifique de l'information sur les relations entre plantes et insectes. Ce mémoire permet aussi de comprendre davantage l'histoire naturelle de l'arpenteuse à tâches mais surtout, il nous informe sur les facteurs qui affectent la préférence alimentaire de l'espèce dans les pruches matures.

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21

Sumpter, Kenton Lucas. "Evaluating a Potential Area-wide IPM Strategy for Managing Hemlock Woolly Adelgid in the Eastern United States." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74873.

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The insecticide imidacloprid, has been found to be highly effective in suppressing hemlock woolly adelgid, Adelges tsugae. Laricobius nigrinus is a predatory beetle released as a biological control of adelgids in the eastern U.S. This project was designed to develop a pest management strategy that utilizes both tactics concurrently within the same site. It will assess the efficiency of this strategy in reducing HWA populations and improving the health of hemlock forests. The project was started in 2010 and data were collected annually through 2016. The project spanned three sites in three different states (KY, WV, and TN). Results show that tree health has generally declined across all sites for each year. HWA population index values are highly variable and are more strongly influenced by the occurrence of low winter temperatures than by treatment effect. Cross-correlation analysis of tree health and HWA population, revealed characteristics of their temporal relationship. In two of the three sites, tree health lagged up to three years behind changes in HWA population, and HWA populations lagged approximately one year behind changes in tree health. L. nigrinus did not establish at any site as of 2016. The lack of sustained recovery of the beetle may be attributable to the occurrence of extremely cold temperatures during the winters of 2014 and 2015 which produced subsequent crashes in the HWA population at two of the three sites. In TN, the L. nigrinus population may have never established due to a decline in the HWA population shortly after release.
Master of Science in Life Sciences

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22

Krapfl, Kurt J. "IMPACTS OF HEMLOCK WOOLLY ADELGID ON TSUGA CANADENSIS FOREST COMMUNITIES IN GREAT SMOKY MOUNTAINS NATIONAL PARK, USA." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/175.

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Tsuga canadensis (L.) Carr. (eastern hemlock), a long lived and shade tolerant coniferous tree species native to eastern North America, is currently threatened by the hemlock woolly adelgid (Adelges tsugae Annand, HWA). This exotic, invasive insect poses a serious threat to T. canadensis stands throughout their native range. The loss of this unique tree species is often coupled with numerous ecological consequences. HWA-induced mortality has exceeded 95% in some forest types, and will likely continue to decimate T. canadensis populations in the coming years. Shortly after HWA was found in Great Smoky Mountains National Park (GSMNP), long-term monitoring plots were established across a gradient of T. canadensis associated forest communities to monitor HWA impacts and stand decline. Our objectives were to (1) determine how T. canadensis populations have changed in conjunction with HWA infestation, and (2) document how HWA has affected vegetative community dynamics following five to six years of infestation in GSMNP. We assessed T. canadensis associated overstory communities and determined that crown density, top dieback, and T. canadensis stem density has significantly declined over the observational period. Furthermore, we found that midstory T. canadensis trees were experiencing greater rates of decline than those of the overstory. Even with these losses, overstory and midstory community composition did not significantly change from 2003 to 2008/09. Many studies have documented rapid pulses of understory vegetative productivity in conjunction with T. canadensis defoliation, which often allows increased amounts of solar radiation to reach the forest floor. Although we observed significant T. canadensis mortality at most plots sampled, understory species composition did not significantly change following HWA infestation. We attribute this lack of species response to the overwhelming abundance of Rhododendron maximum in the mid/understory, which restricts increased light from reaching the forest floor despite the formation of small overstory gaps. However, we found that understory composition significantly varied among ecological groupings, and differences were largely associated with soil properties and elevation. Overall, results of this project suggest that T. canadensis may largely disappear from southern Appalachian forests resulting from infestations of HWA. Although community composition of T. canadensis associated stands has not yet been altered, changes are likely to occur as duration of infestation progresses.

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23

Pardy, Shelley Ann. "Influence of balsam fir stand condition on the abundance and diversity of eastern hemlock looper, Lambdina fiscellaria fiscellaria (Guen.) (Lepidoptera: Geometridae) natural enemies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0029/MQ62413.pdf.

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24

Davis, Gina Ann. "Post-release evaluation of Laricobius nigrinus for the biological control of hemlock woolly adelgid in the eastern United States." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77372.

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Laricobius nigrinus is an insect predator introduced into the eastern United States for the biological control of hemlock woolly adelgid, Adelges tsugae. Laricobius nigrinus dispersal characteristics and predation on A. tsugae were evaluated by monitoring its immature life stages that were distinguished from larvae of the native, L. rubidus using a portion of the cytochrome oxidase subunit one gene. Conventional polymerase chain reaction (PCR) followed by restriction fragment length polymorphism produced DNA fragment sizes that were unique to each species. Real-time PCR used a TaqMan assay with two species-specific nucleotide sequence probes labeled with fluorescence molecule VIC or FAM that indicated the DNA template was L. nigrinus or L. rubidus, respectively. Laricobius nigrinus beetles released in the lower hemlock crown (< 7 m) dispersed to the upper crown (>15 m) for oviposition. Four years post-release, its rate of spread into the surrounding forest was 75 m/yr and the number of L. nigrinus detected on hemlock trees was positively correlated with the density of A. tsugae, regardless of proximity to the release area. Adelges tsugae survival rate was lower on release trees than on geographically separated control trees for three years at a L. nigrinus release site in each Pennsylvania and North Carolina. Yet, the density of A. tsugae remained greater on release trees than control trees. In the eastern United States, the average density of A. tsugae was 3.8 times greater than the upper 95% confidence interval in the native range of L. nigrinus and A. tsugae, as observed in Seattle, WA. This contributed to the average ratio of predator to prey remaining 4.6 times lower than the 95% confidence interval observed in WA. Five to seven years post-release, hemlock health of release and geographically separated control trees declined at similar rates, though the average A. tsugae infestation level was 35% greater on release trees at the time of L. nigrinus release. The full efficacy of L. nigrinus predation was likely underestimated because this study assessed experimental release sites. Interactive roles of biotic and abiotic pressures on A. tsugae should continue to be evaluated at L. nigrinus introduction sites.
Ph. D.

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25

Martin, Katherine L. "Ecosystem dynamics in Central Appalachian riparian forests affected by hemlock woolly adelgid." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337364581.

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26

Mausel, Dave L. "Release and monitoring of Laricobius nigrinus (Coleoptera: Derodontidae) for biological control of the hemlock woolly adelgid in the eastern US." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29785.

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Different Laricobius nigrinus Fender release locations, numbers of predators, and timing of release were evaluated for biological control of the hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). It established at 59% of the sites and location was the most important factor related with establishment and abundance, HWA density, and hemlock vigor index. Cold locations had poor establishment or low abundance, declines in HWA density, and increases in hemlock vigor over time. Paired release and control sites detected a predator impact on HWA density, but densities remained high and tree vigor declined. The phenology of L. nigrinus, L. rubidus LeConte, and HWA were studied at a field insectary and the species were highly synchronized. A cage exclusion study showed that HWA survival and density were lower and ovisac disturbance was higher when exposed to predation. To improve L. nigrinus monitoring, we compared beat sheets for adults or branch clipping for immatures, and the host searching behavior of L. nigrinus was studied to understand how it locates a tree and HWA. In the Appalachians, beat sheet sampling resulted in false negatives as larvae were collected by branch clipping. Adults orientated to a tree visually, fed when prey were present and flew when absent, and showed different search patterns on infested versus uninfested trees. In Seattle, both sampling methods detected L. nigrinus because the predator was common. Predator : prey ratios were high at heavily infested sites in Seattle and low in the eastern US, where is has been released recently. Partial life tables were constructed for HWA sistentes at four sites for 2 yr in Seattle. Unspecified causes of nymph and adult mortality were high and L. nigrinus was the dominant predator of ovisacs. Adult L. nigrinus abundance was positively related to HWA density and immature abundance was related to ovisac density, indicating an aggregation and numerical response to its prey. Laricobius nigrinus has not demonstrated complete biological control of HWA to date, but it may do so in the future and continued release is justified.
Ph. D.

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27

D'Arrigo, Rosanne D., William S. F. Schuster, David M. Lawrence, Edward R. Cook, Mark Wiljanen, and Roy D. Thetford. "Climate-Growth Relationships of Eastern Hemlock and Chestnut Oak from Black Rock Forest in the Highlands of Southeastern New York." Tree-Ring Society, 2001. http://hdl.handle.net/10150/251622.

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Three eastern hemlock (Tsuga canadensis (L.) Carr.) and three chestnut oak (Quercus prinus L.) ring-width chronologies were constructed from old-and second-growth stands in the Black Rock Forest in Cornwall. New York, the first developed for the highlands of southeastern New York State. The longest hemlock chronology extends from 1780-1992 and the longest oak chronology from 1806-1994. The oldest trees sampled had minimum ages of 275 and 300 years for hemlock and chestnut oak, respectively. The tree-ring chronologies were compared to monthly temperature and precipitation data from nearby West Point, NY for the 1850s-1990s and to Palmer Drought Severity Indices for 1911-1990. The chronologies provide forest growth information for the period prior to the initiation of meteorological measurements, begun in 1824 at West Point. Black Rock Forest eastern hemlock growth correlates positively with current July and prior September precipitation, with February-March temperature and with prior September Palmer Drought Severity Indices. It correlates negatively with prior June temperature. Black Rock Forest chestnut oak growth correlates positively with current June-July and prior September and December precipitation, with January temperature, and with prior September-October and current June-July Palmer Drought Severity Indices. It correlates negatively with current June-July temperature. The Black Rock Forest tree-ring records and analyses yield useful information for climate reconstruction and for assessing the potential impact of anthropogenic change (e.g. CO₂-induced climate effects, CO₂ and N fertilization, acid deposition, changes in soil chemistry due to atmospheric pollution).

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Kenefic, Laura. "Leaf Area, Stemwood Volume Growth, and Stand Structure in a Mixed-Species, Multi-Aged Northern Conifer Forest." Fogler Library, University of Maine, 2000. http://www.library.umaine.edu/theses/pdf/KeneficLS2000.pdf.

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29

Siderhurst, Leigh A. "Changes in light levels with loss of Eastern Hemlock (Tsuga canadensis) at a Southern Appalachian headwater stream : implications for Brook Trout (Salvelinus fontinalis) /." Full-text of dissertation on the Internet (1.06 MB), 2010. http://www.lib.jmu.edu/general/etd/2010/masters/siderhla/siderhla_masters_04-23-2010_01.pdf.

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30

Heminger, Ariel. "Establishment of Laricobius nigrinus (Coleoptera: Derodontidae) in Virginia and assessment of its impact on hemlock woolly adelgid, Adelges tsugae (Hemiptera: Adelgidae), throughout the eastern U.S." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/79593.

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Management of hemlock woolly adelgid (HWA), Adelges tsugae (Hemiptera: Adelgidae), is currently being implemented through several different methods including the release of host-specific predators such as Laricobius nigrinus Fender (Coleoptera: Derodontidae). Releases of this predator began in 2003. In 2014, an assessment of the efficacy of L. nigrinus at release sites from New Jersey to Georgia. Field sites were chosen based on the presence of moderate to high densities of HWA, that L. nigrinus was released at least four years prior to the start of the study, and that the predator was determined to be established at that site. Three treatments were set up at each of the sites: no cage, closed exclusion cage, and open cage. Three assessments were taken during key points throughout the season in order to monitor both HWA and L. nigrinus populations. Larval predator were recovered from most of the sites in year one and in higher numbers in year two. Many sites at which L. nigrinus were recovered showed high predation rates of HWA in uncaged samples ranging from 1.5 to 47.3% in year one and 0 to 66% in year 2. A survey for L. nigrinus establishment at previous release sites in VA was conducted. These sites date back as far as 2003 and as recently as 2015. Beat sheeting and branch clippings were conducted to recover Laricobius spp. adults and larvae, respectively. The recovered insects were then identified to species through genetic analysis. A mix of the introduced L. nigrinus and the native L. rubidus LeConte (Coleoptera: Derodontidae) were recovered at some sites, and only L. rubidus were recovered from others. Higher numbers of Laricobius were recovered in spring of year two. Overall, tree health in Virginia decreased from spring 2015 to 2016.
Master of Science in Life Sciences

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31

Doherty, Shannon Joele. "Spatio-temporal Patterns in Beaver Pond Complexes as Habitat for Eastern Spotted Newts (Notophthalmus viridescens) in a Hemlock-northern-hardwood Zone in Western New York State." Youngstown State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1452091312.

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32

Turner, Jeffrey W. "High resolution nuclear magnetic resonance investigations of polymethylenic plant biopolymers structural determinations and post-depositional ammonia nitrogen incorporation /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189438308.

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33

Zilahi-Balogh, Gabriella M. G. "Biology of Laricobius nigrinus Fender (Coleoptera: Derodontidae) and its potential as a biological control agent of the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae) in the eastern United States." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29737.

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The biology of Laricobius nigrinus Fender (Coleoptera: Derodontidae) and its potential for control of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Homoptera: Adelgidae) in the eastern United States were investigated. Laricobius nigrinus completed development on HWA in laboratory studies. There are four larval instars. Mean larval consumption was 225.9 and 252.3 HWA eggs at 12 and 18 °C, respectively. Post-aestivation activity period was 36.6 and 30.8 weeks for males and females at 13 °C, respectively. Mean lifetime fecundity was 100.8 eggs over a mean ovipositional period of 13.2 weeks. Laricobius nigrinus is host specific. In paired-choice and no-choice oviposition tests, L. nigrinus laid more eggs in HWA ovisacs than other test species. Laricobius nigrinus consumed more eggs of HWA than eggs of Adelges piceae (Ratzeburg) and Pineus strobi (Hartig) but not of Adelges abietis (L.). In larval development tests, L. nigrinus only completed development on HWA. A two-year field study conducted in British Columbia showed that: 1) the life cycle of HWA in British Columbia is similar to that previously reported in Virginia and Connecticut; 2) L. nigrinus adults undergo an aestival diapause that coincides with the diapause of the first instar HWA sistens. Adult activity beginning in autumn coincides with resumption of development of the sistens generation; 3) oviposition and subsequent larval development of L. nigrinus coincide with oviposition by HWA sistens adults. Temperature-dependent development was determined for egg, larval, pre-pupal and pupal stages of L. nigrinus at five constant temperatures (9, 12, 15, 18 and 21 °C). Development time was inversely proportional to temperature between 9 and 18 °C. Laricobius nigrinus did not complete development at 21 °C. Minimum developmental temperatures for eggs (6.5 °C), larvae (5.1 °C), pre-pupae (3.8 °C), and pupae (3.1 °C) were determined by extrapolation of linear regression equations to the x-intercept. Degree-days calculated for eggs, larvae, pre-pupae, pupae, and egg to adult were 54.6, 161.3, 196.1, 212.8, and 666.7, respectively. The laboratory derived degree-day model for predicting egg hatch was validated with field data collected in British Columbia. Observed median egg hatch at three of four sites over two years was within 15% of the predicted DD value (54.6).
Ph. D.

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Marques, Cota Vieira Ligia Maria. "Pre-release Evaluation of Laricobius osakensis Montgomery and Shiyake (Coleoptera: Derodontidae), a Potential Biological Control Agent for the Hemlock Woolly Adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), in the Eastern United States." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50606.

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Hemlock woolly adelgid, Adelges tsugae Annand, is an invasive pest threatening eastern (Tsuga canadensis (L.) Carrière) and Carolina hemlock (T. caroliniana Englem.) forests in the eastern US. A new predator, Laricobius osakensis Montgomery and Shiyake, has been found in association with A. tsugae in Japan. Laricobius osakensis was evaluated in a series of pre-release studies to assess its potential as a biological control agent for A. tsugae. Host-range studies indicated that L. osakensis is a specific predator that feeds predominantly and reproduces only on A. tsugae. The functional response "prey consumption changes in response to changes in prey density" was similar for both L. osakensis and Laricobius nigrinus Fender adults. However, L. osakensis had a higher numerical response"changes in oviposition in response to changes in prey density"than L. nigrinus. Laricobius osakensis larvae had a higher functional response than L. nigrinus larvae. Laricobius osakensis\' higher numerical and functional response indicates that this species can potentially be more effective than L. nigrinus. In the evaluation of L. osakensis in sleeve cages in the field from December to April high rates of adult survival, feeding, and reproduction were found. A pair of predators in a cage killed on average five adelgids/day. Peak oviposition occurred in March and April. Larvae from eggs placed in the cages reached maturity in 28-50 days, depending on the season, and only 6.7 % died before reaching maturity. Laricobius osakensis was able to survive, feed, develop, and reproduce in USDA cold-hardiness zones 5b and 6a of southwest Virginia. Behavior of L. osakensis and L. nigrinus was qualitatively similar but varied quantitatively. Laricobius osakensis was more active and had a lower association with T. canadensis. Interactions between species were minimal and not detrimental to either. Intrasexual copulation attempts were observed between males and to a lesser extent between females; however, intrasexual interactions were less frequent than intersexual interactions between the two species. Otherwise activity, including oviposition, was not altered by the presence of the other species. These studies indicate that L. osakensis has the potential to be a valuable addition to the natural enemies complex against A. tsugae.
Ph. D.

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35

Jubb, Carrie Sue. "Evaluation of the establishment of predatory beetle, Laricobius nigrinus (Coleoptera: Derodontidae) in Virginia, and assessment of its impact on hemlock woolly adelgid (Hemiptera: Adelgidae) at release sites in the eastern U.S." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/92617.

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The predatory beetle, Laricobius nigrinus Fender (Coleoptera: Derodontidae), has been released in the eastern U.S. since 2003 for the management of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). The establishment of L. nigrinus at release sites in Virginia was assessed in 2017 and 2018. Sampling was performed in both years to determine presence or absence L. nigrinus. Stand level HWA densities, tree health, predator-prey ratios, and Laricobius spp. identifications were also assessed at each site. Laricobius nigrinus established at 82% of sites and was the primary species recovered. HWA densities appeared to decline, and tree health appeared to improve in year two. Predator-prey ratios were lower than those indicated in the native range, however much is left to be understood about the dynamics of this system in its introduced range. A separate two-year study to assess the impact of L. nigrinus on HWA was initiated in 2014 (Phase One) at nine sites in the eastern U.S. Significant predation of HWA sistens ovisacs was demonstrated during this period, therefore, it was continued from 2016-2018 (Phase Two) to provide longer-term evaluations. Predator exclusion cages were used to monitor predator and prey populations. In Phase Two of the study, mean ovisac disturbance rates on no-cage branches were significantly greater than caged branches and were as high as 80%, suggesting that L. nigrinus can have a significant impact on the sistens generation. Microsatellite analysis of Laricobius larvae indicated that L. nigrinus was the primary species recovered at study sites.
Master of Science in Life Sciences
Hemlock woolly adelgid (HWA), an invasive insect native to Asia and western North America, is a significant threat to two native hemlock species in the eastern U.S. Since 2003, a predatory beetle, Laricobius nigrinus, has been released for management of HWA. In biological control programs such as this one, it is important to evaluate the ability of predators to establish and impact prey in areas where they are introduced, as this helps guide future management decisions. As such, a study was conducted to examine the ability of L. nigrinus to establish after being released at 26 locations in Virginia. In those investigations we found that L. nigrinus established at 82% of the sites. Although promising, longer-term studies are needed to understand if the predation of HWA by L. nigrinus helps improve the health of our native hemlocks. A separate two-phase study was carried out from 2014-2016 and 2016-2018 evaluating the impact of L. nigrinus on HWA at nine release sites in the eastern U.S. In Phase Two reported here, cages were used to exclude L. nigrinus on some HWA infested branches while on others, no cage was applied to allow free access to HWA. Comparisons between branches were made to determine the level of predation by L. nigrinus. These studies showed a significant impact by L. nigrinus on the winter generation of HWA with as many as 80% of those insects being attacked on study branches which indicates that this species has potential as an effective predator.

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Dilling, Carla Irene. "Impact of imidacloprid and horticultural oil on non-target phytophagous and transient canopy insects associated with eastern hemlock, Tsuga canadensis (L.) Carrieré, in the southern Appalachians." 2007. http://etd.utk.edu/2007/DillingCarla.pdf.

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Deal, Isaac K. "Life History of hemlock woolly adelgid, Adelges tsugae Annand, on eastern hemlock, Tsuga canadensis (L.) Carriere, in the southern Appalachians and assessment of egg releases of Sasajiscymnus tsugae (Sasaji and McClure) for its management." 2007. http://etd.utk.edu/2007/Theses/DealIsaac.pdf.

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38

Hakeem, Abdul. ""Non-target effect of imidacloprid on the predatory arthropod guild on Eastern hemlock, Tsuga canadensis (L.) Carriere, in the Southern Appalachians"." 2008. http://etd.utk.edu/2008/HakeemAbdul.pdf.

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39

Byrkit, Maggie K. "Predators of hemlock woolly adelgid in northwestern Oregon /." 2004. http://hdl.handle.net/1957/10445.

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40

Walker-Lane, Laura Newman. "The effect of hemlock woolly adelgid infestation on water relations of Carolina and eastern hemlock." 2009. http://www.lib.ncsu.edu/theses/available/etd-11212008-154437/unrestricted/etd.pdf.

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41

McKenzie, Elizabeth A. "Volatile Profiles and Resistance to Herbivory in Eastern Hemlock." 2014. https://scholarworks.umass.edu/masters_theses_2/104.

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Eastern hemlock hosts the hemlock woolly adelgid, an introduced sap-feeding insect that causes rapid deterioration of the host. Like most conifers, eastern hemlock produces a variety of constitutive and induced defenses, primarily terpenoids. To explore the relationship of terpenoid defenses with adelgid infestations, we artificially infested hemlocks at a forest site and a plantation site, and compared their terpenoid concentrations to those in control trees. Infested trees showed lower terpenoid concentrations than control trees, suggesting that eastern hemlock not only fails to induce production of terpenoids in response to adelgid infestation, but becomes less able to produce carbon-based defenses due to loss of carbon resources to the adelgid. Greater light intensity may account for consistently higher terpenoid concentrations at the plantation site, supporting the explanation that carbon limitation restricts terpenoid production. Recent studies have identified a small number of individual eastern hemlock trees that demonstrate relative resistance to the hemlock woolly adelgid. We compared concentrations of terpenoids in susceptible and relatively resistant trees, both in the forest and in propagated cuttings in a common-garden setting. Terpenoid concentrations were higher in twig tissue of resistant versus susceptible trees, across six sampling dates and at both sites. Because the common-garden cuttings were free of herbivores, the higher terpenoid concentrations are interpreted as a constitutive defense. Increased levels of monoterpenes and sesquiterpenes imply an overall increase in the input of carbon precursors to both terpenoid synthesis pathways. This result suggests either an altered growth-defense balance favoring allocation of carbon resources towards production of defenses, or overall greater carbon availability in growing twig tissue of adelgid-resistant eastern hemlock individuals. We contribute detailed terpenoid data to the study of the eastern hemlock – hemlock woolly adelgid system. Our solvent extraction method permits us to examine needle and twig tissues separately, capture minor components at low concentrations, and focus on stored rather than volatilized terpenoids. By relating terpenoid concentrations to insect densities, we explore the relationships of tentatively defensive chemistry to insect population dynamics. The question remains which terpenoids, if any, directly affect hemlock woolly adelgid and what role phenols may play in the system.

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Cook, Frank B. "Liquid chromatography tandem mass spectrometry (LC/MS/MS) determination of the uptake, persistence and metabolism of imidacloprid in treated hemlock trees." 2008. http://proquest.umi.com/pqdweb?did=1594480901&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.

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43

Buck, Stanley E. "Insect fauna associated with eastern hemlock, Tsuga canadensis (L.), in the Great Smoky Mountains National Park." 2004. http://etd.utk.edu/2004/BuckStanley.pdf.

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Thesis (M.S.)--University of Tennessee, Knoxville, 2004.
Title from title page screen (viewed May 18, 2004). Thesis advisor: Paris Lambdin. Document formatted into pages (vii, 76 p. : ill., maps). Vita. Includes bibliographical references (p. 56-65).

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Lynch, Christine Ann. "Established predators of Fiorinia externa Ferris (Hemiptera: Diaspididae) on Eastern Hemlock (Tsuga canadensis (L.) Carriere) in urban and forest sites." 2006. http://etd.utk.edu/2006/LynchChristine.pdf.

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45

Pezet, Joshua D. "Resin Volatiles of Eastern Hemlock Induced by its Non-Native Herbivores." 2013. https://scholarworks.umass.edu/theses/976.

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Eastern hemlock (Tsuga canadensis) is in decline because of infestation by the invasive hemlock woolly adelgid (Adelges tsugae; ‘HWA’) and, to a lesser extent, the elongate hemlock scale (Fiorinia externa; ‘EHS’). Many conifers respond to insect herbivory by inducing oleoresin-based defenses, however it is unknown whether eastern hemlock is capable of this inducible response. We conducted a plantation setting study of artificially infested saplings to determine if feeding by HWA or EHS induces changes in the tree’s volatile chemistry. The induced changes in volatiles we found were unlike the terpenoid-based defenses of related conifers. Only HWA feeding elevated methyl salicylate, a plant signal for systemic acquired resistance, and benzyl alcohol, a known antimicrobial and aphid deterrent. The influence of environmental conditions and tree life-stage on hemlock volatile chemistry, potentially important factors for wild hemlock populations, is unknown. We investigated whether mature and immature forest trees respond to HWA infestation with the same patterns of volatile production as plantation saplings in full sun and amended soils. HWA induced volatile changes comparable to those of plantation saplings, with many-fold benzenoid increases and no terpenoid-based resinosis. Nearly all volatiles were substantially more abundant in forest than plantation trees, suggesting the effect of site conditions should be addressed in investigations of mechanisms operative in HWA-resistant biotypes of eastern hemlock. Our findings represent the first important step toward understanding the influence of inducible phytochemical responses on hemlock susceptibility to exotic pests, and highlight the possibility of salicylic acid-dependent biosynthetic activity in this gymnosperm system.

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Keller, David Aaron. "Associations between eastern hemlock (Tsuga canadensis) and avian occurrence and nest success in the southern Appalachians /." 2004. http://etd.utk.edu/2004/KellerDavidAaron.pdf.

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Thesis (M.S.)--University of Tennessee, Knoxville, 2004.
Title from title page screen (viewed Sept. 22, 2004). Thesis advisor: David Buehler. Document formatted into pages (xiv, 99 p. : ill. (some col.)). Vita. Includes bibliographical references (p. 50-66).

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47

Nuckolls, April Elizabeth. "The effects of hemlock woolly adelgid (Adelges tsugae) damage on short-term carbon cycling in southern Appalachian eastern hemlock (Tsuga canadensis) stands." 2007. http://purl.galileo.usg.edu/uga%5Fetd/nuckolls%5Fapril%5Fe%5F200708%5Fms.

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Kenefic, Laura S. "Leaf area, stemwood volume growth, and stand structure in a mixed-species, multi-aged northern conifer forest /." 2000. http://www.library.umaine.edu/theses/theses.asp?Cmd=abstract&ID=FES2000-001.

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49

Clark, Kennedy H. "Fire regime dynamics following the mid-Holocene hemlock decline in eastern North America." 2010. https://scholarworks.umass.edu/dissertations/AAI3409558.

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Approximately 5,000 years ago, eastern hemlock ( Tsuga canadensis) experienced a sudden, rapid, range-wide decline most probably due to pest, disease, or climate change. An aphid-like defoliating insect, the hemlock woolly adelgid (Adelges tsugae), recently (1950’s) introduced to eastern North America has been spreading across the eastern United States. The adelgid attacks all size and age classes of hemlocks causing up to 95% mortality in affected stands. The potential for another range-wide hemlock decline has raised a number of concerns including the increased threat of wildfire. Altered fuel loadings in modern adelgid-affected stands and the effects of presumably similar changes in fuels and subsequently altered fire regimes following the prehistoric decline are examined. Fuels data from an adelgid-infested stand in Connecticut and an uninfested stand in Massachusetts were used to generate custom fuel models and predict fire behavior in each stand. Sediment cores were extracted from three sites in western Massachusetts and analyzed for fossil pollen and charcoal around the period of the prehistoric decline. Fossil data from two previously studied sediment cores from coastal Maine are included in the analysis. Results demonstrate a clear and highly significant increase in both fuel loadings and predicted fire behavior in the modern, adelgid-affected stand. Three of the coring sites reflect distinct, significant, short-lived increases in charcoal associated with the prehistoric decline; two do not. Results from the first three sites suggesting increased fire activity also were associated with changes in vegetation which indicate disturbance. Increased fire activity after the decline seems most pronounced in areas where fire was common before the decline. Results indicate that fire was not universally a significant factor driving post-decline succession. Research across a broader geographic area is needed to clarify the relationship between fire and hemlock following the mid-Holocene decline, but the results presented here suggest that managers of modern stands affected by the adelgid should include the possibility of intense fires as a threat to landscapes heavily affected by hemlock decline.

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Clark, Kennedy Helm. "Fire Regime Dynamics Following the Mid-Holocene Hemlock Decline in Eastern North America." 2010. https://scholarworks.umass.edu/open_access_dissertations/224.

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Approximately 5,000 years ago, eastern hemlock (Tsuga canadensis) experienced a sudden, rapid, range-wide decline most probably due to pest, disease, or climate change. An aphid-like defoliating insect, the hemlock woolly adelgid (Adelges tsugae), recently (1950’s) introduced to eastern North America has been spreading across the eastern United States. The adelgid attacks all size and age classes of hemlocks causing up to 95% mortality in affected stands. The potential for another range-wide hemlock decline has raised a number of concerns including the increased threat of wildfire. Altered fuel loadings in modern adelgid-affected stands and the effects of presumably similar changes in fuels and subsequently altered fire regimes following the prehistoric decline are examined. Fuels data from an adelgid-infested stand in Connecticut and an uninfested stand in Massachusetts were used to generate custom fuel models and predict fire behavior in each stand. Sediment cores were extracted from three sites in western Massachusetts and analyzed for fossil pollen and charcoal around the period of the prehistoric decline. Fossil data from two previously studied sediment cores from coastal Maine are included in the analysis. Results demonstrate a clear and highly significant increase in both fuel loadings and predicted fire behavior in the modern, adelgid-affected stand. Three of the coring sites reflect distinct, significant, short-lived increases in charcoal associated with the prehistoric decline; two do not. Results from the first three sites suggesting increased fire activity also were associated with changes in vegetation which indicate disturbance. Increased fire activity after the decline seems most pronounced in areas where fire was common before the decline. Results indicate that fire was not universally a significant factor driving post-decline succession. Research across a broader geographic area is needed to clarify the relationship between fire and hemlock following the mid-Holocene decline, but the results presented here suggest that managers of modern stands affected by the adelgid should include the possibility of intense fires as a threat to landscapes heavily affected by hemlock decline.

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