Thesis (M.S.)--University of Tennessee, Knoxville, 2007. / Title from title page screen (viewed on Apr. 9, 2008). Thesis advisor: Jerome F. Grant. Vita. Includes bibliographical references.

Thesis (M.S.)--Villanova University, 2008. / Biology Dept. Includes bibliographical references.

Thesis (M.A.)--Ohio University, August, 2004. / Includes bibliographical references (p. 52-54)

Thesis (M.S.)--Virginia Polytechnic Institute, 1967. / Typescript (photocopy). Vita. Abstract (2 leaves) bound with copy. Includes bibliographical references (leaves 83-89). Also available via the Internet.

Thesis (M.A.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 52-54)

No description available.

The hemlock woolly adelgid (HWA) Adelges tsugae (Annand) (Hemiptera: Adelgidae), has spread throughout most of the range of eastern hemlocks, Tsuga canadensis (L.) and the entire range of Carolina hemlocks, Tsuga caroliniana (Engelman) in eastern North America. Forest managers often implement an integrated pest management (IPM) strategy that combines chemical, silvicultural, and biological control tactics to create a more sustainable and effective approach for managing HWA. Laricobius spp. (Coleoptera: Derodontidae) are the primary biological control agents within IPM scenarios for HWA. Imidacloprid (IMI), the most widely used insecticide for HWA management, is typically applied to the soil below HWA infested trees and breaks down into several metabolites, including two with insecticidal properties; 5-hydroxy imidacloprid (5H-IMI) and imidacloprid-olefin (IMI-OLE). Imidacloprid-olefin is known to be up to 14 times as lethal to HWA as IMI and is produced as imidacloprid is first hydroxylated into 5H-IMI and further metabolized into IMI-OLE. Because Laricobius spp. spends half of its life in aestival diapause in soil below HWA infested trees, there is the potential for these biological control agents to encounter toxic residues within an IPM setting. Imidacloprid and its metabolites are known to cause mortality in Laricobius spp. feeding on HWA from previously treated trees, but the impact of soil applied imidacloprid on their subterranean survivorship has not been studied. Furthermore, there is limited knowledge on the subterranean portion of Laricobius spp. life cycle. The first study determined the depth to which Laricobius spp. burrowed during their subterranean life phase using 3D X-ray microscopy. When held in containers with two differing soil compaction intensities, 0.2 kg/cm2 and 0.5 kg/cm2, Laricobius spp. were found to burrow an average (± SE) of 2.7 ± 1.5 cm and 1.4 ± 1.3 cm deep, respectively. The second study assessed the effect of three different imidacloprid soil treatments; soil injection, soil drench and CoreTect tablets, on the subterranean survivorshiop of Laricobius spp. The soil drench application technique applied in fall 2020 consistently resulted in significantly higher IMI, 5H-IMI, and IMI-OLE residues than the other two treatments over both years of this study (2021 and 2022). The soil injection treatments from both 2020 and 2017 resulted in above average field emergence of beetles in 2021 and 2022, with relatively insignificant residue quantities present. This study suggests that the soil injection treatment method provides a lower level risk of metabolite exposure to Laricobius spp. compared to soil drench and CoreTect tablet imidacloprid application methods. / Master of Science in Life Sciences / In eastern North America, there are two species of hemlock trees whose longevity and unique shade tolerant adaptations are important to the ecosystems within which they are found. Eastern hemlocks range from southeastern Canada to the southern Appalachian Mountains, while Carolina hemlocks are restricted to the southern Appalachians from northern Georgia to Virginia. Since its first formal identification in Richmond, VA in 1951, the hemlock woolly adelgid (HWA) has caused widespread damage and mortality throughout much of the range of eastern hemlocks and the entire range of Carolina hemlocks. HWA consumes nutrients and restricts water flow within the tree, eventually leading to tree mortality. Forest managers typically rely on an integrated approach, that combines chemical applications with the simultaneous release of insects that naturally attack HWA on untreated trees within the same forest setting. Imidacloprid is the most widely used insecticide for HWA management and is typically applied to the soil below HWA infested trees. This insecticide is absorbed through the roots and travels through the tree where HWA feed and die as a result. Laricobius spp., the primary insect consuming HWA on infested trees, spends part of their life in a below ground summer dormancy. Imidacloprid and its secondary compounds are known to cause mortality in Laricobius spp. feeding on HWA from treated trees, but the impact of soil applied imidacloprid on their below ground survivorship has not been studied to date. Furthermore, while extensive studies have taken place to understand the biology of Laricobius spp., there is limited knowledge about their dormant state. In one study, the depth to which Laricobius spp. burrowed during their below ground life phase was determined using 3D X-ray microscopy. In a second study, the effect of three common imidacloprid treatments; soil injection, soil drench, and CoreTect tablets, on below ground survivorship was examined. Laricobius spp. were found to burrow an average (± S.E.) of 2.7 ± 1.5 cm and 1.4 ± 1.3 cm deep in soil compacted at 0.2 kg/cm2 and 0.5 kg/cm2, respectively. Chemical residue quantities were greatest in soil treated with soil drench in fall 2020, and were found to significantly impact Laricobius spp. survival. Overall, survival was the lowest from the soil treated with CoreTect tablets in 2020. Surival was the greatest from soil that received soil injection treatments in both 2020 and 2017 and had relatively insignificant imidacloprid residues present where the insects typically occur in the soil. Findings from this study suggest that imidacloprid application using the soil injection method is a less risky technique for chemical control in an IPM setting when compared to soil drench and CoreTect methods.

The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae) is a small, non-native insect that feeds on hemlock (Tsuga spp.) species native to the eastern United States. One biological control agent, Laricobius osakensis, shows promise due to its voracious feeding on and synchronous life cycle with HWA. This beetle species is originally from Japan and has undergone all the necessary testing while in quarantine, gaining permission for field release in 2010. Field releases began in the fall of 2012 and continued the following fall. Reproduction occurred at the first year's field sites with beetles recovered at both sites the following fall. During the second year of field work, beetle recovery was low due to winter temperatures that caused high HWA mortality. All of the L. osakensis beetles released in the field are first reared in an Insectary on Virginia Tech's campus. To improve health of these beetles during rearing, a series of chemical amendments were added to the water baths where HWA infested cut hemlock branches were placed. HWA samples were taken from each treatment and analyzed for carbon, nitrogen and total carbohydrates and beetles emergence was recorded in relation to prescribed treatment. None of the treatments appeared as the best for improving HWA health, but there were differences between the sampling months within the two years. These differences in month correlate with the biological processes occurring within HWA at these times such as reproduction and preparation for aestivation. No treatment helped increase beetle emergence. / Master of Science in Life Sciences

Thesis (M.S.)--University of Tennessee, Knoxville, 2008. / Title from title page screen (viewed on Mar. 13, 2009). Thesis advisor: Jerome F. Grant. Vita. Includes bibliographical references.

Thesis (M.S.)--University of Tennessee, Knoxville, 2007. / Title from title page screen (viewed on June 4, 2008). Thesis advisor: Paris L. Lambdin. Vita. Includes bibliographical references.