Beech bark disease
   HOME

TheInfoList



OR:

Beech bark disease is a
disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
that causes mortality and defects in
beech Beech (''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to temperate Europe, Asia, and North America. Recent classifications recognize 10 to 13 species in two distinct subgenera, ''Engleriana'' and ''Fagus''. The ''Engle ...
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
s in the eastern
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
,
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
and
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
.Houston, David R., and James T. O'Brien. "Beech Bark Disease." Forest Insect and Disease Leaflet 75(1998) 1-7. 17 Mar 2008 . Tainter, Frank H., and Fred A. Baker . Principles of Forest Pathology. New York, NY: John Wiley & Sons, Inc., 1996.Sinclair, Wayne A., and Howard H. Lyon. Diseases of Trees and Shrubs. 2nd ed. Ithaca, NY: Cornell University Press, 2005. In
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, the disease occurs after extensive bark invasion by '' Xylococculus betulae'' and the beech
scale insect Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the ...
, '' Cryptococcus fagisuga''. Through a presently unknown mechanism, excessive feeding by this insect causes two different
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
(''Neonectria faginata'' (previously ''Nectria coccinea var. faginata'') and ''
Neonectria ditissima ''Neonectria ditissima'' (syn. ''Neonectria galligena'') is a fungal plant pathogen. It causes cankers that can kill branches of trees by choking them off. Apple and beech trees are two susceptible species. Host range ''Neonectria ditissima'' ...
'' (previously ''Nectria galligena'')) to produce annual
canker A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticultur ...
s on the bark of the tree. The continuous formation of lesions around the tree eventually
girdles A belt, especially if a cord or rope, is called a girdle if it is worn as part of Christian liturgical vestments, or in certain historical, literary or sports contexts. Girdles are used to close a cassock in Christian denominations, including ...
it, resulting in canopy death. In Europe, ''N. coccinea'' is the primary fungus causing the infection. Infection in European trees occurs in the same manner as it does in North American trees. Though the disease still appears in Europe, it is less serious today than it once was.


History and distribution

In Europe, beech bark disease was first documented in 1849, while the first North American observation of ''Cryptococcus fagisuga'' occurred in 1890 and the first North American observation of ''Neonectria'' dates to approximately 1900. At first, it was believed that the scale insect was the main cause of the disease. It was not until 1914 that the ''Neonectria'' fungus was associated with the disease. The first outbreak of beech bark disease in North America appeared in
American Beech ''Fagus grandifolia'', the American beech or North American beech, is a species of beech tree native to the eastern United States and extreme southeast of Canada. Description ''Fagus grandifolia'' is a large deciduous tree growing to tall, w ...
(''
Fagus grandifolia ''Fagus grandifolia'', the American beech or North American beech, is a species of beech tree native to the eastern United States and extreme southeast of Canada. Description ''Fagus grandifolia'' is a large deciduous tree growing to tall, w ...
'') in
Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...
around 1920. The disease then started to spread to the south and west. The first case of beech bark disease in the United States was reported in 1929 in
Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət'' English: , ), officially the Commonwealth of Massachusetts, is the most populous U.S. state, state in the New England ...
. By 2004, the disease had spread as far west as Michigan and as far south as western
North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...
.


Mechanism of infection

For beech bark disease to occur, two components are required, an insect and a fungus.


Beech scale insect

The beech scale insect, ''Cryptococcus fagisuga'', is invasive to North America and is host-specific, feeding exclusively on beech trees. It can be observed on the trunk and limbs of the tree as woolly, white tufts that will later develop into broad strips. The woolly, white tufts and broad strips are the colonies of the beech scale insect that are formed in tiny crevices along the bark. An adult beech scale insect has a soft body, is yellow in color, ranges from 0.5 to 1.0 millimeter long, and has an elliptical shape.{{Cite web, title = Beech Bark Disease - FIDL, url = http://www.na.fs.fed.us/spfo/pubs/fidls/beechbark/fidl-beech.htm, website = www.na.fs.fed.us, access-date = 2015-11-23 The beech scale insect also has a stylet that it uses to penetrate the bark of the tree for feeding purposes. There are no male beech scale insects and the female insects reproduce
parthenogenetic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...
ally. In mid to late summer, the beech scale insect lays its eggs and dies. The eggs are pale yellow and are laid on the bark in strings of four to eight eggs. The first-stage
nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...
begin to hatch in late summer and eggs will continue until early winter. They have short antennae and legs, and move around until they find a suitable and safe place to settle down and force their stylet into the bark to begin feeding. At this point, they begin to secrete the woolly wax cover that they use for protection. This is the second stage of their life cycle and when the spring season arrives they
molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
again and become adult females. A second type of scale insect, ''Xylococcus betulae'', which is non-host-specific, is native to North America and causes beech bark disease to a lesser degree than ''Cryptococcus fagisuga''.


Fungi

There are two fungi common to North America that are important to the beech bark disease process. They are ''Neonectria faginata'' and ''Neonectria ditissima''. The primary fungus is ''N. faginata'', though ''N. ditissima'' is very important in some areas. These fungi infect the tree through the wounds caused by the beech scale insect and then begin to produce
spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
. Spores are contained in perithecia, which are red, lemon-shaped fruiting bodies that form in clusters on the bark. These perithecia mature in the fall, and once they have become sufficiently moist, they each release eight spores that are carried by the wind to other beech trees. Even though the perithecia occur on dead bark, they still have the ability to produce viable spores the next year.


Signs and symptoms

The first visible sign of a beech scale insect infestation is a woolly, white, waxy covering that the insect secretes. This sign can be observed covering small areas or most of the tree. The amount of waxy material observed depends on the
population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...
of the beech scale insect on that tree. The ''Neonectria'' fungi also show signs of its presence. An early sign is what looks like a bleeding spot on the tree. A reddish-brown fluid will ooze from the wound site, giving it this appearance. Later, perithecia will form around the dead spot, which is another sign of the disease.
Symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an disease, illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormali ...
of beech bark disease can be observed in the
foliage A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...
and on the bole of the tree. Foliage may become small, sparse and yellowed. Trees that display a thin, weak
crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
may persist for several years but may also die without displaying any symptoms. Noticeable symptoms on the bole are the cracking of the bark, the formation of cankers, and beech snap, in which the trunk snaps above head height, under stress from wind as a result of the fungi weakening the wood.


Management strategies

There are a few controls for beech bark disease. One important management strategy is prohibiting the movement of nursery stock, firewood, or other materials that may harbor the beech scale insect.
Insecticides Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...
, generally not applied under
forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
conditions, are primarily used on high-value
ornamental tree Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that i ...
s. The use of other
organisms In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fungi; ...
as controls is also a possibility. The
ladybird beetle Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as they ...
is a beetle that preys on the beech scale insect. A fungus that
parasitize Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...
s the ''Neonectria'' fungus could also be employed. The problem with using these organisms to control beech bark disease is that their impact on the disease has not been evaluated extensively. In a forest setting, controlling the beech bark disease is too costly. Timely salvage cutting can reduce economic losses of beech in a forest, however it is preferable to avoid cutting disease-resistant trees. In stands where beech bark disease is established, silvicultural best practice is to retain large overstory trees which show visual resistance (no scale, cankers or fungus), remove heavily infested/dying trees and then treat sprouts from infested trees with herbicides. The residual, resistant parent trees are future sources of resistant seed/sprouts. If herbicides are not a viable option, cut all suckers within 1.5 m of a BBD-killed beech tree. Resistance to beech bark disease in a stand may be 1–5% of trees or more, with significant regional variation. A study of 35 sites in three Canadian provinces found resistance rates ranging from 2.2 to 5.7%.Incidence of beech bark disease resistance in the eastern Acadian forest of North America
/ref> Image:BBDtreecover.jpg, Thin, weak crown with yellow foliage. Image:Beech_snap.jpg, Beech snap. Image:Beech_scale.jpg, White, waxy secretions. Image:Bleeding_spot.jpg, Bleeding Spot.


References


External links




U.S. Forest Service: Northeastern Area-Beech Bark Disease



Beech bark disease resistance project on iNaturalist

Species Profile - Beech Bark Disease (''Neonectria'' spp.)
National Invasive Species Information Center,
United States National Agricultural Library The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Located ...
. Fungal tree pathogens and diseases