@misc{venette_ambourn_aukema_jetton_petrice_2024, title={Hosts and impacts of elongate hemlock scale (Hemiptera: Diaspididae): A critical review}, volume={4}, ISSN={["2673-8600"]}, DOI={10.3389/finsc.2024.1356036}, abstractNote={Fiorinia externa Ferris, elongate hemlock scale, was inadvertently introduced to North America from Japan. This insect is particularly problematic on hemlock, Tsuga spp., though it has been reported in association with several other conifers. The evidence that other conifers might be hosts, capable of supporting growing populations of the insect, has not been previously reviewed. Our review confirms that F. externa is an oligophagous pest of members of Pinaceae. Although species of Cupressaceae and Taxaceae have been reported as hosts of F. externa, they seem unable to support population growth of this pest. Evidence of the tree-killing potential of the insect, even on suitable hosts, is remarkably scant. The degree of pest risk posed by F. externa with respect to tree mortality in areas beyond the geographic range of hemlock seems modest, but uncertain.}, journal={FRONTIERS IN INSECT SCIENCE}, author={Venette, Robert C. and Ambourn, Angie and Aukema, Brian H. and Jetton, Robert M. and Petrice, Toby R.}, year={2024}, month={Feb} }
 @article{oten_jetton_coyle_2023, title={Ecology, Impacts, and Management of Common Late-season Defoliators of Southern Hardwoods}, volume={14}, ISSN={["2155-7470"]}, DOI={10.1093/jipm/pmad002}, abstractNote={
 Late-season lepidopteran defoliators in the genera Anisota, Dryocampa, Datana, and Lochmaeus are usually considered minor pests which primarily cause aesthetic damage on hardwood trees in managed and natural areas. While foliage loss late in the season does not typically impact tree health, severe defoliation can occur on individual branches or entire trees, causing great concern to homeowners and land managers. We review the distribution, biology, damage, and management of several native late-season hardwood defoliators in the southeastern United States, including oakworms, mapleworms, yellownecked caterpillars, and variable oakleaf caterpillars. Affected hardwood trees typically leaf out the following spring even after severe defoliation. While management is seldom recommended due to timing or amount of damage, it may be warranted in certain situations. We provide management recommendations for these late-season defoliators, including chemical and nonchemical options for homeowners and land managers.}, number={1}, journal={JOURNAL OF INTEGRATED PEST MANAGEMENT}, author={Oten, Kelly L. F. and Jetton, Robert M. and Coyle, David R.}, year={2023}, month={Jan} }
 @article{mayfield iii_jetton_mudder_whittier_keyser_rhea_2023, title={Silvicultural canopy gaps improve health and growth of eastern hemlocks infested with & nbsp;Adelges tsugae & nbsp;in the southern Appalachian Mountains}, volume={546}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2023.121374}, abstractNote={The hemlock woolly adelgid (HWA, Adelges tsugae Annand) is an invasive forest insect threatening the sustainability of eastern hemlock (Tsuga canadensis (L.) Carrière) in eastern North America. In this study, cutting small gaps in the forest canopy above understory eastern hemlocks was evaluated as a potential tool for use in the integrated pest management of HWA. Two gap sizes and two gap creation methods (felling vs. girdling trees) were assessed for effects on HWA density, hemlock crown health, hemlock growth, and regeneration of competing tree species, at three different latitude groups in the southern Appalachian Mountains. In all three latitude groups, the treatment that removed the most canopy competition (Large Fell) increased the production of new hemlock shoots, reduced the percentage of dead shoots, and increased basal area increment of target hemlocks relative to unreleased trees. Smaller gaps and those that removed fewer competing live trees (Girdle treatments) also improved hemlock health in the southernmost latitude group. Positive effects of canopy gaps on hemlock crown condition and growth occurred despite similar or higher HWA densities on gap-released vs. unreleased trees. In regression analysis, more than half the variability in crown transparency change and basal area growth post-treatment was explained by the competition index of live trees remaining, average HWA density index, and tree size (dominant tree height and hemlock dbh). In the southernmost latitude group, the regeneration density of deciduous species increased significantly in the three years following gap creation and were highest in the Large Fell treatment. Results support the hypothesis that the increased availability of sunlight (and possibly other limited resources) resulting from canopy gaps (radius approximately ¼ to ½ dominant tree height) improves the physiological tolerance of eastern hemlock to HWA infestation and could complement biological control by providing a more stable source of new shoots with adelgid prey for predatory insects.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Mayfield III, Albert E. and Jetton, Robert M. and Mudder, Bryan T. and Whittier, William A. and Keyser, Tara L. and Rhea, James R.}, year={2023}, month={Oct} }
 @article{darr_coyle_jetton_2022, title={Arthropod and Disease Management in Fraser Fir (Pinales: Pinaceae) Christmas Trees in the Southeastern United States}, volume={13}, ISSN={["2155-7470"]}, DOI={10.1093/jipm/pmac001}, abstractNote={Abstract Fraser fir, Abies fraseri [Pursh] Poir., is one of the most desired Christmas tree species owing to its fragrance, physical appearance, and durability. This species represents a major component of the Christmas tree industry in the southeastern United States, with production occurring in North Carolina, Tennessee, and Virginia. Fraser fir production is a multi-million dollar annual industry despite growing in a limited elevational and latitudinal range. Pest management for Christmas trees is notoriously difficult owing to the near zero-tolerance of most pests, even those causing aesthetic damage. Christmas trees are produced in monocultural environments which make them highly susceptible to several arthropod and fungal pests. We review the major pests affecting Fraser fir Christmas tree production, including their biology, symptoms, and scouting procedures, and current management strategies. In general, pest management in Christmas tree production systems has not changed significantly in the last several decades, and still relies heavily on pesticide usage. We propose several areas in need of research that could help Fraser fir Christmas tree producers mitigate the impacts of climate change and potential new pest species, as well as suggest changes to current or potentially novel integrated pest management strategies which have a chance to provide economic and ecological benefits for this industry.}, number={1}, journal={JOURNAL OF INTEGRATED PEST MANAGEMENT}, author={Darr, Molly N. and Coyle, David R. and Jetton, Robert M.}, year={2022}, month={Jan} }
 @article{bohannon_johnson_jetton_oten_2022, title={Phenology and Voltinism of Emerald Ash Borer (Coleoptera: Buprestidae) in Central North Carolina}, ISSN={["1938-2936"]}, DOI={10.1093/ee/nvac088}, abstractNote={Abstract The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), has killed millions of ash (Fraxinus spp.) trees across North America. Classical biological control using introductions of parasitoid wasps may provide a sustainable approach to managing this invasive insect. However, the establishment of parasitoids in the southern United States has been difficult. The phenology of emerald ash borer was studied in central North Carolina to inform biological control efforts that better align with the seasonal availability of susceptible emerald ash borer life stages in the warm climate of this region. Biweekly emerald ash borer life stage assessments were conducted in stands of infested green ash (Fraxinus pennsylvanica Marshall, Lamiales: Oleaceae) over 26 consecutive months (June 2019 through August 2021). Adult trapping was also conducted in these stands in the spring and summer of 2019, 2020, and 2021. Based on these collections, emerald ash borer exhibits a univoltine (1-yr) life cycle. Parasitoid-susceptible larvae (third and fourth instars in galleries) are present from late June through October (∼1,100–3,000 degree days base 10°C) and are mostly absent during the remainder of the year. Parasitoid release timings and the life history of selected parasitoid species should be aligned with this window of host availability to be effective. This characterization of emerald ash borer phenology and voltinism will help improve the timing and effectiveness of management efforts as this forest pest continues to spread in southern North America.}, journal={ENVIRONMENTAL ENTOMOLOGY}, author={Bohannon, G. Ryan and Johnson, Courtney L. and Jetton, Robert M. and Oten, Kelly L. F.}, year={2022}, month={Nov} }
 @article{thomas_tilotta_frampton_jetton_2022, title={Sesquiterpene Induction by the Balsam Woolly Adelgid (Adelges piceae) in Putatively Resistant Fraser Fir (Abies fraseri)}, volume={13}, ISSN={["1999-4907"]}, DOI={10.3390/f13050716}, abstractNote={Fraser fir, Abies fraseri (Pursh) Poir., is a tree endemic to the Southern Appalachians and is found only in a few isolated populations at high elevations. Fraser firs are also cultivated on a commercial scale as Christmas trees. The species is imperiled by an introduced insect, the balsam woolly adelgid, Adelges piceae Ratzeburg (BWA). The insect severely damages Christmas tree crops and has caused substantial Fraser fir mortality in natural stands. Foliar terpenoids are one mechanism of host plant defense against invading insects and may be one focus of future Christmas tree breeding efforts. This study examines the correlation of foliar terpenoids with Fraser fir performance when infested with BWA. GC-MS and GC-FID analysis of artificially infested Fraser fir foliage reveals that increased concentrations of four terpenoid compounds are associated with BWA infestations. Foliar concentrations of two sesquiterpenes, camphene and humulene, are significantly higher in putatively resistant Fraser fir clones than in more susceptible clones after sustained adelgid feeding for a period of 20 weeks. Although it is unclear if the induction of these sesquiterpenes in the host fir is directly contributing to adelgid resistance, these compounds could serve as effective indicators while screening for BWA resistance in future Christmas tree breeding programs.}, number={5}, journal={FORESTS}, author={Thomas, Austin and Tilotta, David C. and Frampton, John and Jetton, Robert M.}, year={2022}, month={May} }
 @article{potter_jetton_whittier_crane_hipkins_echt_hodge_2022, title={Table Mountain Pine (Pinus pungens): Genetic Diversity and Conservation of an Imperiled Conifer}, volume={12}, ISSN={["1938-3738"]}, url={https://doi.org/10.1093/forsci/fxac043}, DOI={10.1093/forsci/fxac043}, abstractNote={
 Table Mountain pine (Pinus pungens Lamb.) is an imperiled tree species endemic to the southern and central Appalachian Mountains. Generally reliant on fire for regeneration, its fragmented but widespread distribution has declined in recent decades. We quantified the genetic diversity of 26 populations across the range of the species using data from seven highly polymorphic simple sequence repeat (SSR) loci. The species was relatively inbred whereas differentiation among populations was relatively low. Differentiation was significantly but weakly associated with geographic distance among populations. We detected minor genetic differences between northern and southern seed collection zones established based on climate similarity. We conducted a series of simulations using SSR data from 498 seedlings, grown from seed collected from five natural stands of Table Mountain pine, to assess the genetic consequences of different strategies for deploying collected seed in ex situ conservation plantings. Results indicated that reducing the number of families in a planting would not substantially affect the conservation of common alleles but would affect the representation of rare alleles and overall allelic richness. These findings add to our limited knowledge of genetic variation across the distribution of this rare conifer and offer some guidance for its effective genetic conservation.
 Study Implications: Most of the results of this study point to an overall lack of genetic structure and geographic differences in genetic variation within Table Mountain pine, most likely the consequence of prolific interpopulation gene flow. The weak genetic differences between northern and southern seed zones indicate that they are not particularly useful for guiding future gene conservation efforts. The results of seedling sampling simulations demonstrated that it may be possible to meet the goals of conservation plantings by including fewer families per population and/or including families without regard to population.}, journal={FOREST SCIENCE}, author={Potter, Kevin M. and Jetton, Robert M. and Whittier, W. Andrew and Crane, Barbara S. and Hipkins, Valerie D. and Echt, Craig S. and Hodge, Gary R.}, year={2022}, month={Dec} }
 @article{bakken_forrester_mladenoff_leggett_juzwik_jetton_2021, title={Mortality patterns following a hickory decline event - Is density reduction key to maintaining bitternut hickory?}, volume={485}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2021.118956}, abstractNote={Bitternut hickory (Carya cordiformis (Wangenh.) K. Koch) is an important component of many hardwood forest systems in the northern hardwood forests of the Lake States. Extensive mortality of the species was observed in a long-term field experimental site in a second growth northern hardwood forest of Wisconsin between 2010 and 2016. We quantified and documented the characteristics of the mortality, investigated the relationship between bitternut hickory density and mortality patterns, and assessed the persistence of hickory regeneration. The presence of a pathogenic fungus (Ceratocystis smalleyi Johnson and Harrington) and hickory bark beetle (Scolytus quadrispinosus Say) were identified as the main cause of mortality in other instances of hickory decline during a similar time period in the Midwest and Northeast. We investigated the role of these agents through post hoc analysis. Tree surveys of mapped stems ≥10 cm dbh conducted periodically from 2005 to 2016 indicated mortality of hickory rose sharply to 35% year−1 from 2010 to 2016. This is a substantial increase in mortality relative to the dominant species at the site (Acer saccharum Marshall, Tilia americana L., and Fraxinus spp.) which was 1.11% year−1 in the same time period. Mortality rates were higher in larger stems (≥20 cm dbh) than smaller stems (10 < 20 cm dbh). Additional analyses evaluated whether mortality rates were affected by localized species composition, using the proportion of hickory stems among neighboring trees. Proportion of hickory stems, diameter, and crown class proved to be statistically important in predicting mortality in individual hickory stems. The density of hickory regeneration in the <30 cm tall height class decreased from 2010 to 2016. Overall the bitternut hickory population significantly declined, especially the larger sized trees, and this decline will have lasting consequences on the persistence of the species in the area. Potential management actions for mitigating impacts of such rapid hickory decline events, mainly selective thinning, are discussed. Methods for maintaining this co-occurring species is increasingly important as several other codominant species in northern hardwood forests are also decreasing.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Bakken, K. A. and Forrester, J. A. and Mladenoff, D. J. and Leggett, Z. and Juzwik, J. and Jetton, R. M.}, year={2021}, month={Apr} }
 @article{matallana-ramirez_goode_bertone_jansta_burks_jetton_frampton_2020, title={AssessingMegastigmus specularis(Hymenoptera: Megastigmidae) infestations in a Fraser fir (Abies fraseri(Pursh) Poir.) clonal seed orchard of the southern Appalachians}, volume={35}, ISSN={["1651-1891"]}, url={http://dx.doi.org/10.1080/02827581.2020.1789733}, DOI={10.1080/02827581.2020.1789733}, abstractNote={ABSTRACT The Christmas tree industry is mainly supplied with seeds from natural stands and genetically improved germplasm from clonal seed orchards (CSOs). Chalcid wasps (Megastigmus spp.) have a negative effect on the value of seedlots by reducing the quantity of viable seeds and represent a risk for national and international seed trade. Seed radiographies, field observations and seed-dissections from 25 Fraser fir (Abies fraseri (Pursh) Poir.) clones were used to determine chalcid infestation in a CSO of the southern Appalachians. We provided direct evidence that Mesopolobus cf. pinus is an ectoparasitoid of M. specularis, proposed a model that linked different aspects of the biology of these species and discussed host–insect phenological relationships. Infestation of seeds in some clones across surveys, suggested a potential genetic component to chalcid wasp's prevalence. Cold and dark rearing regimens were used to identify changes in adult insect emergence after variation of overwinter conditions. Both the frequency and the time of emerging M. specularis adults from seeds were affected by the duration of the treatments but not statistical differences were found for Mesopolobus cf. pinus. We present evidence for the efficiency of a gravity-seed cleaning method eliminating upwards of 95% of chalcid-infested seeds.}, number={8}, journal={SCANDINAVIAN JOURNAL OF FOREST RESEARCH}, publisher={Informa UK Limited}, author={Matallana-Ramirez, Lilian P. and Goode, Kelly and Bertone, Matthew and Jansta, Petr and Burks, Roger and Jetton, Robert and Frampton, John}, year={2020}, month={Nov}, pages={445–455} }
 @article{mayfield_jetton_2020, title={Differential sunlight exposure affects settling behaviour of hemlock woolly adelgid crawlers}, volume={22}, ISSN={["1461-9563"]}, DOI={10.1111/afe.12382}, abstractNote={Abstract}, number={4}, journal={AGRICULTURAL AND FOREST ENTOMOLOGY}, author={Mayfield, Albert E. and Jetton, Robert M.}, year={2020}, month={Nov}, pages={309–318} }
 @article{miniat_zietlow_brantley_brown_mayfield_jetton_rhea_arnold_2020, title={Physiological responses of eastern hemlock (Tsuga canadensis) to light, adelgid infestation, and biological control: Implications for hemlock restoration}, volume={460}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2020.117903}, abstractNote={The rapid loss of eastern hemlock (Tsuga canadensis) in the southern Appalachian Mountains due to hemlock woolly adelgid (Adelges tsugae, HWA) infestation has resulted in substantial changes to ecosystem structure and function. Several restoration strategies have been proposed, including silvicultural treatments that increase incident light in forest understories. We conducted a four-year manipulative field experiment on surviving mid-story hemlock trees to investigate the effects of release from light limitation on HWA infestation and physiological parameters, expecting that higher light levels would improve tree carbon balance. Mixed hardwood forest sites were either previously uninfested with HWA (UN), infested with HWA (I), or infested with HWA and had a history of predatory beetle releases for biological control (I+P). At each site, we identified ten eastern hemlock trees in the mid-story and cut ~15 m radius canopy gaps around half of them while leaving the canopy intact over the other half. We compared short- and long-term indices of carbon gain and stress: leaf net photosynthesis (Anet); leaf fluorescence (Fv/Fm); leaf total non-structural carbohydrate concentration ([TNC]); new shoot growth; HWA density; and basal area growth. We found that trees experienced greater leaf-level stress in gaps and when HWA was actively feeding. Despite being more stressed, trees in gaps fixed 2x more carbon than those in reference conditions. High Anet in the spring translated into high leaf [TNC] in the spring, coinciding with when HWA was actively feeding. Although infested and uninfested trees had similar leaf [TNC] maxima, infestation prevented trees from allocating this carbon to shoot and basal area growth; this was particularly true for reference trees. Greater shoot growth in gap trees translated to greater annual basal area growth—by the end of the study, trees in gaps were growing 9x more than trees in reference conditions, and this was generally regardless of infestation status. In terms of growth and carbon balance, eastern hemlock consistently benefited from the increased light and soil moisture found in gaps; there was inconsistent and rather weak evidence that predator beetles conferred an additional advantage. Our results indicate that silvicultural treatments may improve long-term health and survival of infested trees and that integration of such treatments with existing strategies is worthy of continued exploration.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Miniat, Chelcy Ford and Zietlow, David R. and Brantley, Steven T. and Brown, Cindi L. and Mayfield, Albert E., III and Jetton, Robert M. and Rhea, James R. and Arnold, Paul}, year={2020}, month={Mar} }
 @article{lapham_miniat_mayfield_jetton_brantley_zietlow_brown_rhea_2018, title={Shade and Hemlock Woolly Adelgid Infestation Increase Eastern Hemlock Foliar Nutrient Concentration}, volume={64}, ISSN={["1938-3738"]}, DOI={10.1093/forsci/fxy025}, abstractNote={Tsuga canadensis (L.) Carr. (eastern hemlock) is dying across much of eastern North America from the invasive hemlock woolly adelgid (HWA, Adelges tsugae Annand). Survey studies show that eastern hemlock populations with high foliar nutrient concentrations are associated with low infestation rates, and also suggest that deeply shaded trees may be more susceptible to infestation. Here we examined (1) how foliar nutrient concentration of eastern hemlock changes with varying shade levels; and (2) how nutrient concentration might further change with sustained shade and subsequent HWA infestation. Foliar samples from three years—pretreatment, post-shade, and post-shade and infestation—were collected and analyzed for [N], [P], and [K]. Pretreatment, all seedlings had similar foliar nutrient concentrations. After nine months in the shade tents, seedlings under higher levels of shade exhibited increased foliar [N]. For each 10% increase in shade, foliar [N] increased 35.09 μg/mg over baseline levels. The combined effects of prolonged shade with HWA infestation increased foliar [N], [P], and [K]. The mechanism for increasing foliar nutrients is unknown, but may be due to reduced growth causing a concentration effect, or nutrients mobilized by the plant in response to infestation.}, number={6}, journal={FOREST SCIENCE}, author={Lapham, Marika and Miniat, Chelcy Ford and Mayfield, Albert E., III and Jetton, Robert M. and Brantley, Steven T. and Zietlow, David R. and Brown, Cindi and Rhea, James R.}, year={2018}, month={Dec}, pages={577–582} }
 @article{potter_jetton_bower_jacobs_man_hipkins_westwood_2017, title={Banking on the future: progress, challenges and opportunities for the genetic conservation of forest trees}, volume={48}, ISSN={0169-4286 1573-5095}, url={http://dx.doi.org/10.1007/s11056-017-9582-8}, DOI={10.1007/s11056-017-9582-8}, number={2}, journal={New Forests}, publisher={Springer Nature}, author={Potter, Kevin M. and Jetton, Robert M. and Bower, Andrew and Jacobs, Douglass F. and Man, Gary and Hipkins, Valerie D. and Westwood, Murphy}, year={2017}, month={Mar}, pages={153–180} }
 @article{bucholz_frampton_jetton_tilotta_lucia_2017, title={Effect of different headspace concentrations of bornyl acetate on fecundity ofgreen peach aphid and balsam woolly adelgid}, volume={32}, ISSN={["1651-1891"]}, DOI={10.1080/02827581.2016.1275769}, abstractNote={ABSTRACT Balsam woolly adelgid (Adelges piceae) (Hemiptera: Adelgidae) (BWA) is an exotic pest introduced from Europe to North America in the early 1900s. Subsequent introductions and spread have enabled this pest to infest native Fraser fir stands in the Southern Appalachians and become a troublesome pest for the region’s Christmas tree industry. Means to study its fecundity and control it are consequently of high importance. Headspace solid phase micro-extraction coupled with gas chromatography and mass spectrometry were used to compare chemical differences in stem tissue between a resistant species, Veitch fir (Abies veitchii) and the susceptible Fraser fir (Abies fraseri). Comparisons demonstrated that bornyl acetate (BA), a terpenoid, was qualitatively more abundant in resistant Veitch fir than Fraser fir. Varying headspace concentrations of BA were tested to ascertain any biological impacts on egg eclosion of BWA, as well as fecundity of green peach aphid (Myzus persicae) (GPA), an insect serving as a proxy. Varying concentrations of BA and a known number of adelgid eggs did not indicate any impact of concentration on egg eclosion success. However, defoliated Veitch fir branches in treatment jars produced a significant negative impact on BWA eclosion success. Implications of these findings are discussed.}, number={5}, journal={SCANDINAVIAN JOURNAL OF FOREST RESEARCH}, author={Bucholz, Ethan and Frampton, John and Jetton, Robert and Tilotta, David and Lucia, Lucian}, year={2017}, pages={397–405} }
 @article{brantley_mayfield_jetton_miniat_zietlow_brown_rhea_2017, title={Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings}, volume={385}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2016.11.028}, abstractNote={The rapid loss of eastern hemlock (Tsuga canadensis) due to infestation with hemlock woolly adelgid (Adelges tsugae, HWA) has greatly altered structure and function of eastern forests. Numerous control strategies including local pesticide use and biocontrol with predator beetles have been implemented with considerable cost and varying success. Silviculture treatments that increase incident light on surviving hemlock trees to reduce infestation and ameliorate carbon starvation have been proposed as another possible conservation strategy, yet no controlled studies have evaluated the coupled plant-insect responses to increased light. We conducted a nursery experiment on artificially infested eastern hemlock seedlings under varying levels of ambient light, ranging from 0 to 90% shade. We measured HWA infestation (ovisac density), short- and long-term indicators of carbon balance (leaf chlorophyll fluorescence, net photosynthesis, total nonstructural carbohydrate content, and shoot growth), and nutrition (leaf N content). We hypothesized that higher light would result in reduced HWA densities, higher C assimilation rates, and improved tissue non-structural carbohydrate balance; and these effects would ameliorate the effects of infestation on C balance and lead to improved seedling growth. HWA density decreased with increasing light, and was highest in the 90% shade treatments. However, photosystem II efficiency and net assimilation were also lower under the higher light treatment. Despite tradeoffs between reduced infestation and reduced leaf function from higher light, and little variation in sugar content among treatments, both leaf and root starch content and seedling growth were higher under the higher light treatment. Increasing light levels improves long-term carbon balance for hemlock seedlings in the presence of HWA. Although hemlock typically occurs in deeply shaded forests, our results suggest that silvicultural treatments such as forest thinning that increase light exposure may reduce HWA abundance and lead to better tree C balance, and may be an effective component of large-scale conservation and restoration strategies.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Brantley, Steven T. and Mayfield, Albert E., III and Jetton, Robert M. and Miniat, Chelcy F. and Zietlow, David R. and Brown, Cindi L. and Rhea, James R.}, year={2017}, month={Feb}, pages={150–160} }
 @article{potter_campbell_josserand_nelson_jetton_2017, title={Population isolation results in unexpectedly high differentiation in Carolina hemlock (Tsuga caroliniana), an imperiled southern Appalachian endemic conifer}, volume={13}, ISSN={1614-2942 1614-2950}, url={http://dx.doi.org/10.1007/s11295-017-1189-x}, DOI={10.1007/s11295-017-1189-x}, number={5}, journal={Tree Genetics & Genomes}, publisher={Springer Nature}, author={Potter, Kevin M. and Campbell, Angelia Rose and Josserand, Sedley A. and Nelson, C. Dana and Jetton, Robert M.}, year={2017}, month={Sep} }
 @article{hastings_potter_koch_megalos_jetton_2017, title={Prioritizing conservation seed banking locations for imperiled hemlock species using multi-attribute frontier mapping}, volume={48}, ISSN={0169-4286 1573-5095}, url={http://dx.doi.org/10.1007/s11056-017-9575-7}, DOI={10.1007/s11056-017-9575-7}, number={2}, journal={New Forests}, publisher={Springer Nature}, author={Hastings, John M. and Potter, Kevin M. and Koch, Frank H. and Megalos, Mark and Jetton, Robert M.}, year={2017}, month={Mar}, pages={301–316} }
 @article{powers_mayfield_frampton_jetton_2015, title={Comparison of Suspended Branch and Direct Infestation Techniques for Artificially Infesting Hemlock Seedlings with the Hemlock Woolly Adelgid for Resistance Screening}, volume={6}, ISSN={["1999-4907"]}, DOI={10.3390/f6062066}, abstractNote={The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive forest pest in eastern North America that has caused significant decline and mortality in populations of eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (T. caroliniana Engelm.). The breeding of adelgid-resistant genotypes for reforestation activities is still in the early development phases, and most resistance screening programs have depended on labor-intensive direct artificial infestation techniques for introducing adelgids to target seedlings. We investigated the timing and effectiveness of a potentially less labor-intense suspended branch infestation technique compared to two levels of a direct infestation method. Results indicated that peak crawler emergence from adelgid infested hemlock branches occurred within a 10 to 14 day period and that crawler emergence was higher from non-hydrated compared to hydrated branches. Greater infestation pressure was achieved when using progrediens crawlers compared to sistens crawlers. In 2013, when the infestation attempts were most successful, the suspended branch technique induced the same or higher adelgid densities on target seedlings as the direct infestation techniques. Assuming an initial investment in infrastructure, the suspended branch approach could be a more time and cost effective method for inducing adelgid infestations for resistance screening of large numbers of candidate trees.}, number={6}, journal={FORESTS}, author={Powers, Zaidee L. and Mayfield, Albert E., III and Frampton, John and Jetton, Robert M.}, year={2015}, month={Jun}, pages={2066–2081} }
 @article{jetton_mayfield_powers_2014, title={Development of a rain down technique to artificially infest hemlocks with the hemlock woolly adelgid, Adelges tsugae}, volume={14}, DOI={10.1673/031.014.106}, abstractNote={Abstract The hemlock woolly adelgid Adelges tsugae Annand (Hemiptera: Adelgidae), is a non-native invasive pest that has caused widespread decline and mortality of eastern hemlock (Tsuga canadensis (L.) Carr. (Pinales: Pinaceae)) and Carolina hemlock (T. caroliniana Engelm.) in the eastern United States. Our preliminary experiments evaluated the utility of a rain-down technique to induce artificial infestations of A. tsugae on hemlock seedlings en masse. Experiments were conducted in PVC (1 m3) cages topped with poultry wire for placement of A. tsugae-infested branches, and with 1 m2 gridded glue sheets and/or hemlock seedlings placed below to capture adelgid abundance, distribution, and infestation rate data. In the March 2011 experiment, the density of progrediens crawlers (adelgid nymphs, first instars) that rained down inside the PVC cages was significantly higher in the high ovisac treatment compared to the low ovisac treatment, with an estimated 513,000 and 289,000 crawlers per m2 falling beneath each treatment, respectively. Resulting A. tsugae infestation rates on Carolina hemlock seedlings placed inside the cages did not differ between the treatments but were at or above established damage threshold densities for the adelgid. Infestation rates on eastern hemlock seedlings that were placed in cages nine days after the experiment started were below damage threshold levels and did not differ between the treatments. In the May 2011 experiment, the density of sistens crawlers raining down was substantially lower, with 17,000 and 33,000 falling per m2 in the low and high ovisac treatments, respectively. Resulting infestation rates on Carolina hemlock seedlings were extremely low and well below damage threshold levels. Although A. tsugae crawlers were well distributed across the 1 m2 gridded glue sheets placed at the bottom of each cage, hot spots of unusually high crawler density did occur in both experiments. This rain-down technique shows potential for use in an operational tree-breeding program where screening large numbers of hemlock seedlings for resistance to A. tsugae is required.}, journal={Journal of Insect Science (Tucson, AZ)}, author={Jetton, R. M. and Mayfield, A. E. and Powers, Z. L.}, year={2014} }
 @article{jetton_robison_2014, title={Effects of artificial defoliation on growth and biomass accumulation in short-rotation sweetgum (Liquidambar styraciflua) in North Carolina}, volume={14}, DOI={10.1673/031.014.107}, abstractNote={Abstract Sweetgum, Liquidambar styraciflua L. (Hamamelidales: Hamamelidaceae), is a species of interest for short-rotation plantation forestry in the southeastern United States. Despite its high levels of resistance to many native insects and pathogens, the species is susceptible to generalist defoliators during outbreak epidemics. The objective of this field study was to evaluate the potential impact of defoliation on sweetgum growth and productivity within the context of an operational plantation. Over three growing seasons, trees were subjected to artificial defoliation treatments of various intensity (control = 0% defoliation; low intensity = 33% defoliation; moderate intensity = 67% defoliation; high intensity = 99% defoliation) and frequency (not defoliated; defoliated once in April of the first growing season; defoliated twice, once in April of the first growing season and again in April of the second growing season). The responses of stem height, stem diameter, stem volume, crown volume, total biomass accumulation, and branch growth were measured in November of each growing season. At the end of the first growing season, when trees had received single defoliations, significant reductions in all growth traits followed the most severe (99%) defoliation treatment only. After the second and third growing seasons, when trees had received one or two defoliations of varying intensity, stem diameter and volume and total tree biomass were reduced significantly by 67 and 99% defoliation, while reductions in stem height and crown volume followed the 99% treatment only. All growth traits other than crown volume were reduced significantly by two defoliations but not one defoliation. Results indicate that sweetgum is highly resilient to single defoliations of low, moderate, and high intensity. However, during the three-year period of the study, repeated high-intensity defoliation caused significant reductions in growth and productivity that could have lasting impacts on yield throughout a harvest rotation.}, journal={Journal of Insect Science (Tucson, AZ)}, author={Jetton, R. M. and Robison, D. J.}, year={2014} }
 @inproceedings{jetton_dvorak_potter_whittier_rhea_2011, title={Genetics and conservation of hemlock species threatened by the hemlock woolly adelgid}, booktitle={Proceedings of the 30th Southern Tree Improvement Conference}, author={Jetton, R. M. and Dvorak, W.S. and Potter, K. M. and Whittier, W. A. and Rhea, J.}, year={2011}, pages={81–87} }
 @article{jetton_monahan_hain_2011, title={Laboratory studies of feeding and oviposition preference, developmental performance, and survival of the predatory beetle, Sasajiscymnus tsugae on diets of the woolly adelgids, Adelges tsugae and Adelges piceae}, volume={11}, journal={Journal of Insect Science (Tucson, AZ)}, author={Jetton, R. M. and Monahan, J. F. and Hain, F. P.}, year={2011} }
 @article{potter_jetton_dvorak_hipkins_rhea_whittier_2011, title={Widespread inbreeding and unexpected geographic patterns of genetic variation in eastern hemlock (Tsuga canadensis), an imperiled North American conifer}, volume={13}, ISSN={1566-0621 1572-9737}, url={http://dx.doi.org/10.1007/s10592-011-0301-2}, DOI={10.1007/s10592-011-0301-2}, abstractNote={Eastern hemlock (Tsuga canadensis [L.] Carr.) is an ecologically important tree species experiencing severe mortality across much of its eastern North American distribution, caused by infestation of the exotic hemlock woolly adelgid (Adelges tsugae Annand). To guide gene conservation strategies for this imperiled conifer, we conducted a range-wide genetic variation study for eastern hemlock, amplifying 13 highly polymorphic nuclear microsatellite loci in 1,180 trees across 60 populations. The results demonstrate that eastern hemlock exhibits moderate inbreeding, possibly a signature of a prehistoric decline associated with a widespread insect outbreak. Contrary to expectations, populations in formerly glaciated regions are not less genetically diverse than in the putative southern refugial region. As expected, peripheral disjunct populations are less genetically diverse than main-range populations, but some are highly genetically differentiated or contain unique alleles. Spatially explicit Bayesian clustering analyses suggest that three or four Pleistocene glacial refuges may have existed in the Southeastern United States, with a main post-glacial movement into the Northeast and the Great Lakes region. Efforts to conserve eastern hemlock genetic material should emphasize the capture of broad adaptability that occurs across the geographic range of the species, as well as genetic variability within regions with the highest allelic richness and heterozygosity, such as the Southern Appalachians and New England, and within disjunct populations that are genetically distinct. Much genetic variation exists in areas both infested and uninfested by the adelgid.}, number={2}, journal={Conservation Genetics}, publisher={Springer Nature}, author={Potter, Kevin M. and Jetton, Robert M. and Dvorak, William S. and Hipkins, Valerie D. and Rhea, Rusty and Whittier, W. Andrew}, year={2011}, month={Dec}, pages={475–498} }
 @inproceedings{potter_jetton_dvorak_frampton_rhea_2010, title={Ex situ seed collection represents genetic variation present in natural stands of Carolina hemlock}, booktitle={Proceedings of the Fifth Symposium on Hemlock Woolly Adelgid in the Eastern United States}, author={Potter, K.M. and Jetton, R.M. and Dvorak, W.S. and Frampton, J. and Rhea, J.}, year={2010}, pages={181–190} }
 @inproceedings{jetton_dvorak_whittier_potter_2009, title={Genetics and conservation of hemlock species threatened by the hemlock woolly adelgid}, booktitle={Proceedings of the 20th U.S. Department of Agriculture Interagency Research Forum on Invasive Species}, author={Jetton, R.M. and Dvorak, W.S. and Whittier, W.A. and Potter, K.M.}, year={2009}, pages={39–40} }
 @misc{jetton_dvorak_whittier_2008, title={Ecological and genetic factors that define the natural distribution of Carolina hemlock in the southeastern United States and their role in ex situ conservation}, volume={255}, ISSN={["0378-1127"]}, DOI={10.1016/j.foreco.2008.01.032}, abstractNote={Carolina hemlock (Tsuga caroliniana Engelm.) is a rare endemic found in the Appalachian Mountains and Upper Piedmont of the southeastern United States. It is being decimated by the hemlock woolly adelgid (Adelges tsugae Annand), an exotic pest introduced into the region from Japan several decades ago. We examine ecological, genetic and climatic factors in natural stands that characterize the species’ occurrence to better determine where ex situ conservation plantings should be established. To facilitate species/site matching, we use FloraMap™ software that quantifies climatic variables at provenance collection sites to predict other areas where Carolina hemlock could be planted in the U.S. and Latin America. Results indicate that based on analysis of 15 populations, Carolina hemlock is found on predominantly sandy-clay loam soils but occurs on a wider range of soil textural groups than previously thought. Its natural occurrence represents two different climatic groups, with the Cradle of Forestry, NC site most different than the rest. FloraMap™ predicts with high probability that Carolina hemlock populations can be successfully moved to central Chile, and with lower probability to the Ozark region of Arkansas and southern Brazil. Camcore, North Carolina State University, has now collected seeds from 12 provenances and 77 mother trees in natural populations of Carolina hemlock and distributed these to the three regions listed above. Our goal is to sample 150 trees from the 15 provenances which will sample most of the species’ genetic diversity for ex situ conservation. The ex situ approach offers an alternate means of protecting the species if efforts to control the adelgid fail in the southeastern US.}, number={8-9}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Jetton, Robert M. and Dvorak, William S. and Whittier, W. Andrew}, year={2008}, month={May}, pages={3212–3221} }
 @article{jetton_hain_dvorak_frampton_2008, title={Infestation Rate of Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Among Three North American Hemlock (Tsuga) Species Following Artificial Inoculation}, volume={43}, ISSN={["0749-8004"]}, DOI={10.18474/0749-8004-43.4.438}, number={4}, journal={JOURNAL OF ENTOMOLOGICAL SCIENCE}, author={Jetton, Robert M. and Hain, Fred P. and Dvorak, William S. and Frampton, John}, year={2008}, month={Oct}, pages={438–442} }
 @inproceedings{jetton_whittier_dvorak_potter_2008, title={Status of ex situ conservation efforts for eastern and Carolina hemlock in the southeastern United States}, booktitle={Proceedings of the 4th Symposium on Hemlock Woolly Adelgid}, author={Jetton, R.M. and Whittier, W.A. and Dvorak, W.S. and Potter, K.M.}, year={2008}, pages={81–89} }
 @article{potter_dvorak_crane_hipkins_jetton_whittier_rhea_2007, title={Allozyme variation and recent evolutionary history of eastern hemlock (Tsuga canadensis) in the southeastern United States}, volume={35}, ISSN={0169-4286 1573-5095}, url={http://dx.doi.org/10.1007/s11056-007-9067-2}, DOI={10.1007/s11056-007-9067-2}, abstractNote={Eastern hemlock (Tsuga canadensis [L.] Carr.) is a widespread and ecologically important conifer species of eastern North America that is threatened by the hemlock woolly adelgid (Adelges tsugae Annand), a pest introduced into the United States from Asia in the 1920s. Information about the genetic composition of eastern hemlock is necessary to guide ex situ conservation efforts in the southeastern United States, where the species is expected to harbor relatively high amounts of genetic variation in areas of Pleistocene glacial refuge. Nineteen allozyme markers were used to quantify the genetic variation present in 20 eastern hemlock populations in the southeastern United States. Results indicate that the species has low levels of genetic diversity in the region compared to most other conifers, but greater population differentiation (F ST = 0.126). Populations along the eastern periphery and in the Appalachian interior exhibited higher levels of diversity than those along the western periphery of its geographic range. The results suggest that the glacial refuge area for eastern hemlock was likely located east of the southern Appalachian Mountains, and indicate that ex situ conservation seed collections should be concentrated in these areas of higher diversity.}, number={2}, journal={New Forests}, publisher={Springer Nature}, author={Potter, K. M. and Dvorak, W. S. and Crane, B. S. and Hipkins, V. D. and Jetton, R. M. and Whittier, W. A. and Rhea, R.}, year={2007}, month={Oct}, pages={131–145} }
 @article{jetton_frampton_hain_2005, title={Vegetative propagation of mature eastern and Carolina hemlocks by rooted softwood cuttings}, volume={40}, number={5}, journal={HortScience}, author={Jetton, R. M. and Frampton, J. and Hain, F. P.}, year={2005}, pages={1469–1473} }