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Beech Bark Disease in American Beech Trees (Fagus grandifolia)

Identification of an American beech tree (Fagus grandifolia):

Smooth bark of an American beech tree.

Smooth bark of an American beech tree.

Beech trees can be found in upland areas of a mature deciduous forest. The identification of a beech tree can be done year round with the use of five criteria appearing continually or seasonally:

Bark

Beech trees stand out by their thin, smooth, grey bark.

Leaf

The leaves persist late into the winter. The single, oval leaves alternate along the twig with straight, feather-like arranged venation, with toothed margins. They also have a plastic-like texture.

Bud

There is a minimum of three bud scales per bud, overlapping one over the next. The buds are hairless, glossy, and smooth. They are stalkless and are attached directly to the base.

The nut and leaf of the American beech tree.

The nut and leaf of the American beech tree.

Flowers

The flower opens typically in spring, along with leaf development.  The flowers are either male or female, with either single, inferior ovaries or a set of nine or more stamens. The flowers are arranged in a cluster, directly attached directly to the twig.

Fruit

The fruit of beech trees develops into a nut, which is then surrounded by a spiny series of modified leaves (Fagus”, 2013).

American Beech Tree: Reproduction and Range

The American Beech tree has a range that extends from Nova Scotia, across Maine, southern Quebec, Ontario, Northern Michigan, and to far south parts of Texas and Florida. The American Beech is often a dominant or co-dominant tree species in its habitat.  Trees typically grow to between 20-25 metres and can live up to 300 years.  Beech trees reproduce both sexually and asexually.  In sexual reproduction, trees produce seeds when they are between 40-60 years old every 2 to 8. Fruiting occurs in September to October and seeds are released in October to November after frost.  Dispersal is limited and most seeds simply fall to the ground and are unviable if they have not germinated (in early spring to early summer) within a year (Coladonato, 1991).  In vegetative reproduction, new trees can sprout from stumps or suckers sent up from roots (Smallidge, 2009).

North American range of the Beech tree. (Image from http://en.wikipedia.org/wiki/File:Fagus_grandifolia_map.png)

North American range of the Beech tree. (Image from http://en.wikipedia.org/wiki/File:Fagus_grandifolia_map.png)

American Beech Tree: Beech Bark Disease

Beech Bark Disease (BBD) is a fast-spreading illness afflicting countless populations of beech trees (Randall, 2007). BBD is readily observable in the Morgan Aboretum.  BBD is the result of an insect-fungi complex that involves the Beech scale insect (Cryptococcus fagisuga), an invasive species introduced to eastern North America from Europe in the 19th century, as well as the Neonectria fungi (Neonectria faginata or N. galligena) (Houston and O’Brien, 1983). The scale pierces the bark in order to access the tree’s sap, enabling the fungi to infect the tree through these openings in the bark, leading to the creation of lesions and potential disruption of the tree’s nutrient and water transport process (Wieferich, 2011).  Consequently, these effects of infection can lead to leaf and bark loss, and eventually, to the death of the tree.  The scale reproduces rapidly in late summer and fall and is spread among Beech tree populations by wind mainly, but also by wildlife and human activities (Houston, 1994).

Left: Beech tree with Neonectria fungal colonization. Right: Beech tree with severe bark loss.

Left: Beech tree with Neonectria fungal colonization. Right: Beech tree with severe bark loss.

American Beech Tree: Uses & Importance

The American beech tree serves both ecological and economic significance. The flowering structures of this tree eventually develop into beechnuts, or beechmasts, which are a source of food for birds and various mammals, such as mice, squirrels, black bear, deer, etc (Coladonato, 1991). The wood of the beech tree is also exploited through the forestry industry, due to its sturdiness and resistance to decay (Gilman and Watson, 1993). Increasing mortality of the American beech tree due to Beech Bark Disease is an ecological concern since numerous species depend on these trees for food and shelter. A loss of American beeches would thus lead to a decline in wildlife habitat and food supply for a variety of species (“Wildlife”, 2013).

Beech Bark Disease: Research question

BBD team assessing the severity of disease in a younger beech tree.

BBD team assessing the severity of disease in a younger beech tree.

Our research has two main components: size and density of the beech tree.

Which factor, size or density, has a higher correlation with beech bark disease severity in the individual tree?

If we see a greater correlation between Beech Bark Disease and tree size, we can speculate that the disease is related to the age or development stage of the beech trees. By determining the density of the beech trees in our plots, we can then further investigate the spatial and tree-to-tree interactions of the disease.

Research methods:

To measure the density and tree size in relation to beech bark disease severity, we first chose four areas of study: two with majority beech populations and two with mixed beech and maple population. Within each of these areas, three random points were selected using GPS software. From each of these points, a 12m x 12m square plot was measured and the diameter at breast height was measured.

Measuring the diameter of the beech trees using diameter tapes.

Measuring the diameter of the beech trees using diameter tapes.

After each tree was measured, it was assessed for severity of beech bark disease. The severity was based on five characteristics: presence of scale, presence of cankers, presence of fungus, amount of bark loss, and amount of leaf loss. Each of these characters was then given a rating from 0-2, with zero being absent, 1 being low presence (<50%), and 2 being high presence (>=50%). These five ratings were then added together to give an overall disease scale from 0-10. By measuring the diameter and disease severity of every beech tree in a standard plot size, we were able to not only compare the severity of individual trees to their individual sizes, but also compare the average disease severity in each plot to the density as determined by the number of trees in the plot.

Beech Bark Disease: Severity Scale

References:

Coladonato, Milo. “Index of Species Information: Fagus grandifolia.” Fire Effects Information System. USDA Forest Service, 1991. Web.

“Fagus grandifolia.” GoBotany. New England Wild Flower Society, n.d. Web. 19 Oct. 2013. <https://gobotany.newenglandwild.org/species/fagus/grandifolia/&gt;.

Gillman, Edward F. and Dennis G. Watson. “Fagus grandifolia: American Beech.” Fact Sheet ST-423. Florida: Insitute of Food and Agricultural Sciences, University of Florida, 1993. Web.

Houston, David R. and James T. O’Brien. “Beech Bark Disease.” Forest Insect and Disease Leaflet.  Washington: U.S. Department of Agriculture Forest Service, 1983. Web.

Houston, David R. “Major New Tree Disease Epidemics: Beech Bark Disease.” Annual Review of Phytopathology 32 (1994): 75-87. Web.

Randall, Morin S., Andrew M. Liebhold, Patrick C. Tobin, Kurt W. Gottschalk, and Eugene Luzader. “Spread of beech bark disease in the Eastern United States and its relationship to regional forest composition.” Canadian Journal of Forest Research 37.4 (2007): 726-736. Web.

Smallidge, Peter J. “Woodland Guidelines for the Control and Management of American Beech.” Forest Connect: Fact Sheet Series. ForestConnect.info. Department of Natural Resources, Cornell University Cooperative Extension, 2009. Web.

Wieferich, Daniel J., Deborah G. McCullough, Daniel B. Hayes, and Hancy J. Schwalm.  “Distribution of American Beech (Fagus grandifolia) and Beech Scale (Cryptococcus fagisuga Lind.) in Michigan from 2005 to 2009.” Northern Journal of Applied Forestry 28.4 (2011): 173-179. ProQuest. Web.

“Wildlife habitat.” Backyard Conservation Tip Sheet. Washington: U.S. Department of Agriculture, Natural Resources Conservation Service. Web. 19 Oct. 2013.

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About Crystal Ernst

Hakai Institute postdoctoral scholar at Simon Fraser University (B.C.)

2 comments on “Beech Bark Disease in American Beech Trees (Fagus grandifolia)

  1. Thanks for this post! Very interesting… i have a question: I know some research is being done to assess whether or not vegetative propagation might work to help save the beech trees -did you come across any information about this? What’s the potential of this approach to helping our beloved beech trees?

  2. Hi there!
    We’re currently reading up on the vegetative propagation idea (ex. tissue cultures, grafting), and it really seems interesting. The ability to create successful grafts of resistant beech trees would be awesome in establishing a more vigorous gene pool of beech trees… However, it seems like there are various challenges to first select disease-trees whose resistance is genetically-based, and to achieve a higher rate of successful and consistent grafts that can be propagated on a mass scale.

    Hmm, further research has to be done on scale colonization and genetically-based resistance, but let’s hope that it does hold some potential for helping our beech friends!

    Thanks a lot for the comment!

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