Beech Bark Disease

[See also pages on beech leaf disease (BLD) and beech leaf-mining weevil (BLMW)]

 

Beech Bark Disease (BBD)

Although beech trees are utilized by a wide variety of insects and fungi, at least until discovery of beech leaf disease at the beginning of the 21st Century, only one disease was considered to pose a significant threat – beech bark disease (Beckman et al. 2021). Reed et al. (2022) consider beech leaf disease to be the primary threat for beech seedlings and saplings while beech leaf disease and European beech scale combined are the primary concern for overstory beech trees.

The Disease

Beech bark disease (BBD) is a disease complex arising from the interaction of the non-native beech scale insect, Cryptococcus fagisuga, and several associated fungi, e.g., Neonectria faginata, Neonectria ditissima, and Bionectria ochroleuca (Beckman et al. 2021; see several discussions of disease progression, e.g., Houston, in USFS GTR NE-331). The scale insect penetrates the bark during feeding, enabling associated fungus to enter the tree. The multiple cankers girdle the tree (Houston and Valentine, 1988). Of the fungi, N. galligena is native; N. coccinea var. faginata is widely thought to be introduced (Lovett et al. 2006). Since N. galligena is established in northern hardwood forests, where it inhabits other species of trees, it is usually first to take advantage of damage caused by the scale. This infestation can cause “full blown” disease. Later, N. coccinea var. faginata usually displaces N. galligena (Houston in USFS GTR NE-331; Witter in USFS GTR NE-331).

Beech scale was introduced into Halifax, Nova Scotia, in the late 1800’s. It probably entered on imported nursery stock of European beech (Hawbolt, 1944). The disease took years to become apparent but was commonplace in Nova Scotia by 1930. The cause was not understood until it was studied intensively by John Ehrlich, a Canadian graduate student at Harvard. Houston (in USFS GTR NE-331) reports that Ehrlich’s 1934 publication named the disease, described the causal insect/fungus complex, and laid the groundwork for later studies. In the 1920s, 90% of beech trees > 3 inches dbh in the affected Canadian Maritime forests he studied were infected by the fungus. In some cases, tree mortality quickly followed infection. In other cases, mortality extended over decades.

The first report of BBD in the United States occurred at the Arnold Arboretum in Massachusetts in 1929 (Houston and Valentine, 1988; Rumble et al. 2020). The disease was thought to have been established for ten years at the time of its detection (Rumble et al. 2020). BBD had established near New York City by 1934 (Houston in USFS GTR NE-331, citing Ehrlich). Houston suggest that these detections might document several separate introductions.

Spread and Extent

In the 90+ years since detection in the US, beech scale has continued to spread, followed – sometimes decades later – by beech bark disease. By the late 1950’s, BBD had been detected throughout New England and into eastern Pennsylvania (Rumble et al. 2020). For example, BBD had infected nearly 90% of beech trees in the Bartlett Experimental Forest in the White Mountains of New Hampshire by 1950 (Ducey et al. 2023). As it did so, the structure and function of affected forests also changed. By the 21st Century, the aftermath zone (see below) was well developed in most of the beech forests of the Maritime Provinces and Maine, in some forests of Vermont, New Hampshire, and in New York. It was developing in a few of the longest-affected forests of Pennsylvania and West Virginia as well (Houston in USFS GTR NE-331).

Transport of the scale and associated fungus over long distances – probably by people – resulted in isolated outbreaks being detected in the 1980’s. These outbreaks were in West Virginia (1981), Virginia (1983), Ohio (by 1984), and south to the North Carolina-Tennessee border (by 1986) (Houston and Valentine, 1988); Michigan followed in 2000 (Rumble et al. 2020). Scientists believe the disease was probably present in Michigan at least 15 to 20 years earlier (Witter et al. 2004).

Spread of BBD in the western portions of the range of American beech has occurred more slowly in the Great Lakes region than in areas to the east (Reed et al. 2022). The scale is much more widespread than the full disease. The scale was detected in Ontario in 1960, and in western New York, Pennsylvania, and Ohio in 1984; by 2022, the scale was present on 60% of beech trees in southwestern Ontario and 38% of trees in these American states. However, only 4% of trees in the Great Lakes region of both countries were infected with Neonectria cankers (Reed et al. 2022).

BBD is now well established in all beech-dominated forests in the U.S., though it occurs on less than 30% of American beech’s full distribution (Beckman et al. 2021). Beech makes a good firewood (Heyd, 2004; Witter et al. 2004); firewood movement may be associated with anthropogenic spread.

Impacts of BBD

This insect-disease complex has caused extensive mortality in an ever-larger proportion of the range of American beech. The disease progresses through three stages:

• “Advancing front” – beech scale invading, building up populations. This stage precedes actual disease and can be much more widely distributed. Reed et al. (2022) found that while by 2022 the scale was present on 60% of beech trees in southwestern Ontario and 38% of trees in western New York, Pennsylvania, and Ohio, only 4% of trees in the same region were infected with Neonectria cankers.
• “Killing phase” – during this phase, various Neonectria fungi begin penetrating the bark and infecting trees. Mortality of the mature beech stems is sometimes rapid, sometimes protracted over decades (Lovett et al. 2006). Up to 90% of American beech trees eventually succumb (Lovett et al. 2006; Beckman et al. 2021).
• “Aftermath phase” – stand dynamics reflect the reduced vigor and premature mortality of beech trees chronically infected with the disease. Tree decline is usually gradual; vacated canopy space is filled by either lateral expansion of neighboring trees or growth of saplings in the understory. Multiple young beech stems sprout from the roots, but the disease also infects these stems as they mature (Lovett et al. 2006).

The disease first attacks large, old trees in unmanaged forests (Houston, 2004; Latty, 2004; Witter et al. 2004). Scientists suggest several reasons:

• Contiguous forest stands might facilitate spread of the scale (Witter et al. 2004) – although Liebhold et al. (2004) could find no evidence that BBD spreads faster in regions with higher concentrations of beech trees.
• The dense shade and moist conditions in forests with a major hemlock component might favor high scale fecundity (Latty, 2004).
• The older trees’ bark has several characteristics that facilitate scale establishment such as rough surface (Witter et al. 2004) and higher nitrogen content (Houston, 2004). Although this bark is sometimes thicker, that has not protected those trees from disease (Van Leaven et al. 2004).
• Older trees often have significant tree wounds, broken crowns or extensive areas of decay; all provide sites that the scale can utilize (Witter et al. 2004).

Latty (2004) raised several other possible factors. First, did the chronic elevated nitrogen deposited in Eastern forests by air pollution favor spread of the scale, since nitrogen is important in the diet of sucking insects? Second, did the larger canopy gaps formed by spongy moth defoliation favor regeneration by beech or sugar maple? Finally, she asks whether the milder winters and drier falls expected as the climate changes might promote greater fecundity of the scale?

At high elevations in the Great Smoky Mountains, beech form a globally rare plant community. This community is now threatened by BBD (present for more than 30 years) as well as rooting by non-native hogs (Rumble et al. 2020).

In parts of eastern Canada, New England, and New York, more than 100 years after its introduction, BBD is still causing changes in forest stand structure and composition (Evans et al. 2004). The disease can apparently trigger a state of change from diverse, productive forests to nearly monotypic, self-perpetuating, stands of scrub beech – sometimes called “beech hell”. However, in some stands the process seems to have stabilized in a less-affected condition, with retention of most size classes of multiple tree species. These continue to support much of the native biodiversity.

In these aftermath forests, remaining beech are prone to damage by windthrow and ice. Breakage by these forces promotes root sprouting. It is likely that as these sprouts mature, they will succumb to BBD (Latty, 2004; Canham, 2004) or beech leaf disease.

Loss of large beech trees has been expected to result in reduced production of beechnuts with follow-on impacts through the food chain (e.g., Storer et al. 2004). However, field studies have not always supported this expectation. A study in an unmanaged, 250-year-old northern hardwood stand in the central Adirondacks found that, despite BBD-caused loss of large beech trees, more beechnuts were produced in the stand during the period 1994-2003 than in 1988-1993 (McNulty and Masters, 2004). However, another study, using stand data from 1948, found that by 1989, beechnut production had decreased by 37% (Houston, 2004). Storer et al. (2004) said that, as of 2004, the evidence suggested that mast production does not differ significantly between healthy and infected forests. At the same time, small mammal species diversity was higher in healthy beech forests than either BBD-infected forests or forests without beech.

It is unclear whether widespread mortality of beech and increasing abundance of sugar maple always results in a change in beech foliar biomass or overall lignin content of leaf litter. Griffin et al. (2004) found that increasing dominance of sugar maple was correlated with increases in: 1) litter decomposition rates, 2) nitrification fraction, 3) *15N in soils, and 4) nitrate leaching in soil solution. These, in turn, caused increasing rates of carbon turnover and nitrogen cycling in soils, especially production of nitrate. This change would alter the ability of these forests to retain atmospherically deposited nitrogen. Latty (2004) found the opposite: that the high mortality of large beech was countered by advance regeneration of beech. However, the widespread mortality of beech saplings caused by beech leaf disease is likely to undermine this balancing, possibly strengthening the results of changes documented by Griffin et al. (2004).

Latty (2004) also expected more coarse woody debris on the forest floor, although she noted the paucity of baseline data. In some stands in the Adirondacks she found 64% of downed woody beech debris in old-growth stands and 75% in maturing stands, which was attributable to BBD-induced death. McNulty and Masters (2004) also found that down woody material increased in abundance, but it was of smaller size. They thought that the size difference might affect small mammal and salamander populations that rely on dead woody material for feeding sites and cover.

Interactions with other Non-native Pests

Beech bark disease is invading forests in which other non-native pests have had severe impacts. One question is which tree species are most likely to replace beech. Several studies have documented the importance of hemlock in both facilitating BBD (above) and in the aftermath forest (Latty, 2004; Lovett et al. 2006; Beckman et al. 2021). However, hemlocks in these forests have suffered widespread mortality caused by the hemlock woolly adelgid. To date, no studies have estimated how the severe decline of hemlocks might affect future evolution of the aftermath forests.

A smaller impact will probably result from similar levels of mortality of white ash, due to the emerald ash borer, because ash are much less abundant than hemlock. Ash is, however, mentioned by several authors as a forest component in, for example, Ontario (Reed et al. 2020) and Michigan (Kearney, McCullough, and Walters, 2004).

The maples – sugar maple (Acer saccharum) and red maple (A. rubrum) – are not currently under pressure by non-native pests. However, Latty (2004) noted that sugar maple, while able to respond to gap openings, also experienced very high mortality when in subcanopy sizes. In some parts of the Northeast, red oak (Quercus rubra) is affected by oak wilt. Two conifers that in some places might replace beech, red spruce (Picea rubens) and balsam fir (Abies balsamea), also face non-native pests. The brown spruce longhorned beetle (Tetropium fuscum) is established in Nova Scotia one part of New Brunswick (more info. here) so not yet near New England. The balsam woolly adelgid (Adelges piceae) kills some balsam fir in the Northeastern U.S. and eastern Canada.

The recently detected pest beech leaf disease presents the greatest quandary. This disease attacks principally the very seedlings and saplings that now constitute a growing proportion of American beech presence in the forest. Despite its much more recent detection (2012 compared to early 20th Century), BLD has already become pervasive in forests surrounding Lake Erie in the U.S. and Ontario. BLD symptoms are already more widely distributed than BBD – although not the scale. Reed et al. (2022) consider beech leaf disease to be the primary threat for beech seedlings and saplings while beech leaf disease and European beech scale combined are the primary concern for overstory beech trees. Scientists are just beginning to explore how this new invader will affect forests in the “aftermath” stage following principal mortality phase of beech bark disease.

Place of American Beech in the Forest

American beech, Fagus grandifolia, is one of the most widely distributed hardwoods in North America. Its range reaches from Nova Scotia to Texas, and in the north, west to the Mississippi River (Houston in USFS GTR NE-331; Beckman et al. 2021). Beech averages 2.3% of the total forest basal area within its range. Population densities are highest in a broad band of maximum abundance following the Appalachian Mountains from Kentucky to Maine. Beech constitutes 11.1% or more of basal area in this band, and up to 51% in parts of the Adirondack Mountains. While data from the Canadian range is spottier, in 2004 beech made up 17% of the forest in Quebec (Cogbill in USFS GTR NE-331). In 2019, American beech comprised more than 50% of basal area in 17 plots and between 20-50% basal area in 16 additional plots in southwestern Ontario (Reed et al. 2022). In much of the southern and Midwestern portion of the range, beech constitute less than one percent of basal area (Cogbill in USFS GTR NE-331). Human actions even before the advent of non-native pests and pathogens had exacerbated a centuries-old reduction in beech. Population densities in the Northeast at the beginning of the 21st Century was only 30% of that at the beginning of the 19th Century. Still, despite overall reduction and regardless of past history, as of the beginning of the 21st Century, northern hardwood landscapes tended to have beech in 70 – 100% of stands; beech formed 5 – 25% of basal area (Cogbill in USFS GTR NE-331). Even in Michigan, on the western edge of the species’ range, there were an estimated 138 million beech trees on 7.16 million acres of forest. About half of these forest areas had a beech basal area greater than 20% before arrival of beech bark disease (Heyd in USFS GTR NE-331).

Fagus grandifolia is the only native member of the genus in North America (Beckman et al. 2021). There is a disjunct population in eastern Mexico (Beckman et al. 2021) – sometimes considered a separate subspecies, Fagus grandifolia var. mexicana (Cogbill in USFS GTR NE-331).

Throughout its range, beech is found on most mesic sites which have escaped fire. Trees grow from sea level along the Atlantic and Gulf coasts up to 2000 m elevation in gaps of the southern Appalachian Mountains. At the northern edge of the range, beech occurs under locally moderated temperature and moisture conditions up to ~ 800 meters on mountain slopes. It is especially abundant on well drained soils in valley sides or on hardwood ridges. The western limit of the range appears to be tied to moisture availability (Cogbill, USFS GTR NE-331). Due to its extensive distribution, the species has not been considered at risk by the International Union for the Conservation of Nature or The Nature Conservancy (Beckman et al. 2021).

Beech’s modern geographic pattern reflects the interaction of three major factors: the species’ background regional abundance, alterations due to land use changes (e.g., land clearance, regeneration of agricultural lands, forest management), and – since the mid-20th Century – the effects of beech bark disease. Past land use affects light levels. Canopy beech promote soil and forest floor conditions that favor regeneration by beech seedlings over competitors, e.g., sugar maple and hemlock (Beckman et al. 2021; Lovett et al. 2006). In some of these forests, white ash also comprised significant proportions of the forest (e.g., 5% of saplings, 16% of seedlings in plots in southwestern Ontario [Reed et al. 2023] and also present in Michigan forests [Kearney et al. 2004]) until succumbing to emerald ash borer. Still, beech seeds and sprouts are not dispersed far from the parent tree, which to some extent limits its ability to exclude other tree species availability of soil nutrients (especially nitrogen and calcium) (Canham, in USFS GTR NE-331). Soil moisture is important because beech is highly sensitive to drought stress. On moist, acidic soils, beech competes overwhelmingly in late-successional stands. Beech uninfected by beech bark disease are highly resistant to wind damage. American beech is often said to be long-lived, although Cogbill (USFS GTR NE-331) said field studies have found few trees over 250 years old. Beech foliar litter is high in lignin so it decomposes more slowly than that of its principal hardwood co-dominants, yellow birch and sugar maple. Litter quality influences the development of the forest floor and affects nutrient retention and cycling in the stands (Lovett et al. 2006).

Despite the decline of American beech historically (see above) and 100 years of impacts from beech bark disease, the species is expanding in regenerating forests across many parts of the Eastern Deciduous Forest (Ducey et al. 2023; Miller et al. 2023; Payne and Peet, 2023). One factor might be that deer browse beech leaves and twigs only when other food sources are scarce [see National Deer Association article here]. Deer are documented as playing a significant, if not always dominant, role in regeneration of forest tree species (Miller et al. 2023; Blossey et al. 2024). Deer do feed on the nuts, apparently heavily (Storer et al. 2004).

American beech has limited value as timber, but it is recognized as very important to wildlife. The tree’s large nuts are high in both protein (20% dry matter) and fat (50% dry matter) [see National Deer Association article here ], making them an important food source for at least 20 wildlife species, (perhaps as many as 40) including rodents, certain passerine birds, turkey, and bear among others (McNulty and Masters, 2004). The nuts’ importance is greatest in those parts of the northern hardwood forest where oaks are rare; there, beeches are the only species producing hard mast (Lovett et al. 2006). However, mast resources are apparently not as “reliable” as has often been said. In Maine and New York – after arrival of beech bark disease – large mast crops are produced on alternate years (Jakubas et al. 2004; McNulty and Masters, 2004). In Michigan, before arrival of beech bark disease, less than 10% of beech nuts examined were sound (Storer et al. 2004).

In addition to challenges from three non-native pests – beech bark disease, beech leaf disease, and European beech leaf weevil, beech might be struggling to adapt to elevated nitrogen deposited in eastern forests by air pollution (Latty, 2004).

Future of Beech

The most direct impact of beech bark disease on American beech has been to shift the tree from a large, canopy-forming, old tree to dense tangles of root sprouts. Sometimes, as in the Catskill Mountains at the beginning of the 21st Century, the overall abundance of beech and sugar maple did not change, but their distribution across elevations did (Griffin et al. 2004).

Lovett et al. (2006) expected longer-term, centuries-long changes in forest composition, even if it was delayed. They expected that these changes would have important consequences for carbon and nitrogen cycling and food web dynamics in northern hardwood forests where dying beech are replaced by growing numbers of sugar maple (Acer saccharum), yellow birch (Betula alleghaniensis), and eastern hemlock (although – see above information on hemlock woolly adelgid). In some areas, other tree species might be restored. In fully stocked (unthinned) stands on the Monongahela National Forest, MacKenzie (2004) expected beech stands to revert to red spruce – the species which dominated the forest before being logged out at the beginning of the 20th Century. MacKenzie (2004) raised one caveat: climate change. He did not mention brown spruce longhorned beetle, which is spreading slowly south from Nova Scotia. Beech leaf disease had not yet been detected so its impact was also not assessed.

Management

Managing the aftermath stands full of “defective” beech sprouts has proved difficult – even without consideration of beech leaf disease. The objective is often to increase the proportion of beech resistant to BBD. However, American beech’s ecological characteristics (e.g., extreme shade tolerance, longevity, prolific seed production and aggressive root sprouting) make it difficult to manipulate through silviculture. The undesired results of harvesting are described by Houston (2004), and expanded upon by McNulty and Masters (2004) as well as Ostrofsky (2004). Ostrofsky (2004) found that while clearcuts produced more vigorous and resistant American beech seedlings, these seedlings were highly susceptible to decline and death from exposure in the absence of protection by surrounding trees.

USFS scientists and managers developed a conservation priority-setting framework for forest tree species at risk from pest & pathogens and other threats. The Project CAPTURE (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation) uses FIA data and expert opinion to group tree species under threat by non-native pests into vulnerability classes and specify appropriate management and conservation strategies. The scientists prioritized 419 tree species native to the North American continent. The analysis identified 15 taxonomic groups requiring the most immediate conservation intervention because of the tree species’ exposure to an extrinsic threat, their sensitivity to the threat, and their ability to adapt to it. Each of these 15 most vulnerable species, and several additional species, should be the focus of both a comprehensive gene conservation program and a genetic resistance screening and development effort.  Exotic beech scale insect is not known to be a threat to any of these 15 most vulnerable species. 

Breeding

In the absence of disturbance, it is thought that sexual reproduction is the most common form of reproduction throughout most of its range, whereas asexual reproduction of beech occurs mainly in beech gaps of the Smoky Mountains and in more severe environments in the northern and western parts of its range (Petrillo and Witter, 2004). Beech sprouts generally occur when the roots are injured which is more abundant on exposed south-facing slopes where freeze-thaw activity can damage any shallow roots (Petrillo and Witter, 2004). In MI, significantly more beech regeneration occurs in stands dominated by sugar maple and American beech than in stands with a strong northern red oak (Quercus rubra) component (oak-beech).

Beckman et al. (2021) report that one to three percent of beech trees have some resistance to beech scale insect attacks. The presence of apparent resistance – even at this low level – was recognized decades ago (Houston, 2004). Scientists have sought methods to identify, breed, and propagate American beech trees resistant to beech scale (the prime dispersal agent). Koch and Carey (2004) and Loo et al. (2004) describe these efforts and the difficulties they had to overcome. Beckman et al. (2021) report that USFS researchers have succeeded in developing methods to identify, breed, and propagate American beech trees resistant to beech scale and had established seed orchards.

Beech leaf disease has upended all of this progress. The USFS is now trying to develop methods to screen trees for resistance to BLD, specifically to the nematode (J. Koch, USFS, pers. comm.).

The breeding effort is supported by The Nature Conservancy thanks to a grant from a private foundation which includes breeding efforts for several other species including white, black, and green ash as well as eastern hemlock. Strategies to protect existing genetic diversity of imminently imperiled tree species, and advocacy for long-lasting funding, research, proactive research & development programs. Much of this work will be through convening stakeholders to carry out these strategies.

Efforts to mitigate the widespread, significant, and lasting impacts of beech bark disease have received little attention from governmental and industrial forestry stakeholders (Twery, 2004; Evans et al. 2004; Gardner, 2004). These authorities suggest several reasons:

• the species is not valued for timber production;
• the species is not declining in abundance, but, rather, regenerating prolifically; and
• the species has less value as an ornamental than do some other species under threat from non-native pests, e.g., hemlock.

Sources

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., and Westwood, M. 2021. Conservation Gap Analysis of Am beech. Lisle, IL: The Morton Arboretum. August 2021

Blossey, B., Hare, D., and Waller, D.M. 2024. Where have all the flowers gone? A call for federal leadership in deer management in the US. Front. Conserv. Sci., 5:1382132. doi: 10.3389/fcosc.2024.1382132

Cammermeyer, J. 1993. Life’s a beech – and then you die. Am. Forests, July/August 1993, Pp. 20-21, 46.

Cogbill, C.V. 2004. Historical Biogeography of American Beech. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Ducey, M.J, Fraser, O.L., Yamasaki, M., Belair, E.P., and Leak, W.B. 2023. Eight decades of compositional change in a managed northern hardwood landscape. Forest Ecosystems, 10(3) 100121. https://doi.org/10.1016/j.fecs.2023.10012

Evans, C.A., Lucas, J.A., Twery, M.J., and Twardus, D.B. 2004. Summary and Conclusions. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Griffin, J.M., Lovett, G.M., Robinson, G.R., Arthur, M.A., Weathers, K.C., and Kudish, M. 2004. Sugar Maple and Beech Dynamics in Beech Bark Disease Aftermath Forests of the Catskill Mountains, New York. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Hawbolt, L. S. 1944. History of spread of beech scale, Cryptococcus fagi (Baerensprung), an insect intro to the Maritime provinces. Acadian Nat., 1: 137-146.

Heyd, R.L. 2004. Managing Beech Bark Disease in Michigan. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Houston, D.R. 2004. Beech Bark Disease: 1934 to 2004: What’s New Since Ehrlich? In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Houston, D. R., and Houston, D. B. 2000. Allozyme genetic diversity among Fagus grandifolia trees resistant or susceptible to BBD in natural pops. Can. J. For. Res., 30: 779-789.

Houston, D. R. and Valentine, H. T. 1988. BBD: the temporal patterns of cankering in aftermath forests of Maine. Can. J. For. Res., 18: 38-42.

Jakubas, W.J., McLaughlin, C.R., Jensen, P.G., and McNulty, S.A. 2004. Alternate Year Beechnut Production and Its Influence on Bear and Marten Populations. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Kearney, A., McCullough, D.G., and Walters, M. 2004. Impacts of Beech Bark Disease on Understory Composition in Michigan. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Koch, J.L. and Carey, D.W. 2004. The Genetics of Resistance of American Beech to Beech Bark Disease: Knowledge Through 2004. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Latty, E.F. 2004. Stand-Level Patterns and Ecosystem Consequences of Beach (sic) Bark Disease. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Liebhold, A., Morin, R., Gottschalk, K., and Twardus, D. 2004. The Biogeography of Beech Bark Invasion of North America. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Loo, J., Ramirez, M., and Krasowski, M. 2004. American Beech Vegetative Propagation and Genetic Diversity. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Lovett, G.M., Canham, C.D., Arthur, M.A., Weathers, K.C., and Fitzhugh, R.D. 2006. Forest Ecosystem Responses to Exotic Pests and Pathogens in Eastern North America. www.biosciencemag.org might 2006 / Vol. 56 No. 5 • BioScience 395

MacKenzie, M. 2004. Survival of the Fittest: Beech Bark Disease-Resistant Beech Will Leave More Offspring. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Mahony, E. M., Milgroom, M. G., and Sinclair, W. A. 1999. Origin, genetic diversity and pop structure of Nectria coccinea var. faginata in North America. Mycologia, 91: 583-592.

McNulty, S.A. and Masters, R.D. 2004. Changes to the Adirondack Forest: Implications of Beech Bark Disease on Forest Structure and Seed Production. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Miller, K.M., Perles, S.J., Schmit, J.P., Matthews, E.R., Marshall, M.R. 2023. Overabundant deer and invasive plants drive widespread regeneration debt in eastern United States national parks. Ecological Applications, 2023;33:e2837. https://onlinelibrary.wiley.com/r/eap Open Access

Payne, C.J. and Peet, R.K. 2023. Revisiting the model system for forest succession: Eighty years of resampling Piedmont forests reveals need for an improved suite of indicators of successional change. Ecological Indicators, 154 (2023) 110679

Petrillo, H.A., and Witter, J.A. 2004. Regneration of American beech (Fagus grandifolia ehrh.) in Michigan: Interactions of beech bark disease and management practices, (pp142-145). IN Beech bark disease: proceedings of the Beech Bark Disease Symposium: Saranac Lake, New York, June 16-18. USDA, Forest Service, Gen. Tech. Report NE 331.

Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., and Crane, B.S. 2019. Prioritizing the conservation needs of US tree spp: Evaluating vulnerability to forest insect and disease threats, Global Ecology and Conservation, doi: https://doi.org/10.1016/

Reed, S.F., Volk, D., Martin, D.K.H., Hausman, C.E., Macy, T., Tomon, T., S. Cousins. 2022. The distribution of beech leaf disease and the causal agents of beech bark disease (Cryptoccocus fagisuga, Neonectria faginata, N. ditissima) in forests surrounding Lake Erie and future implications. Forest Ecology and Management, 503 (2022) 119753

Rumble, L., G. Taylor, J.B. Grinath, A.B. Morris. 2020. Measuring spatial and temporal shifts in forest structure and composition in high elevation beech forests in response to beech bark disease in Great Smoky Mountains National Park. Forest Ecology & Management, 461 (2020) 117954

Schlarbaum, S. E. September 2002. Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN., personal communication.

Shigo, A. L. 1964. Organism interactions in the beech bark disease. Phytopathology, 54: 263-269.

Storer, A.J., J.N. Rosemier, B.L. Beachy, and D.J. Flaspohler. 2004 Potential Effects of Beech Bark Disease and Decline in Beech Abundance on Birds and Small Mammals. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Sweeney J.D., Hughes, C., Zhang, H., Hillier, N.K., Morrison, A. and Johns R. (2020) Impact of the Invasive Beech Leaf-Mining Weevil, Orchestes fagi, on American Beech in Nova Scotia, Canada. Frontiers in Forests and Global Change, | www.frontiersin.org 1 April 2020 | Volume 3 | Article 46

Twery, M.J. 2004. Foreward In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Van Leaven, K. and C.A. Evans. 2004. A Preliminary Examination of Beech Bark Disease and the Influence of Soil Moisture on Bark Thickness and Disease Status in the Northern Adirondack Uplands. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004

Witter, J.A., Stoyenoff, J.L., Petrillo, H.A. , Yocum, J.L. , and Cohen, J.I.. 2004. Effects of Beech Bark Disease on Trees and Ecosystems. In USDA USFS NE Research Station General Technical Report NE-331 BBD: Proceedings of the BBD Symposium Saranac Lake, NY June 16 – 18, 2004