Chestnut Blight Life Cycle – Tips On Treating Chestnut Blight
By: Jackie Carroll
In the late nineteenth century, American chestnuts made up more than 50 percent of the trees in Eastern hardwood forests. Today there are none. Find out about the culprit– chestnut blight– and what’s being done to combat this devastating disease.
Chestnut Blight Facts
There is no effective method of treating chestnut blight. Once a tree contracts the disease (as they all eventually do), there is nothing we can do but watch it decline and die. The prognosis is so bleak that when experts are asked how to prevent chestnut blight, their only advice is to avoid planting chestnut trees altogether.
Caused by the fungus Cryphonectria parasitica, chestnut blight tore through Eastern and Midwestern hardwood forests, wiping out three and a half billion trees by 1940. Today, you can find root sprouts that grow from old stumps of dead trees, but the sprouts die before they are mature enough to produce nuts.
Chestnut blight found its way into the U.S. in the late nineteenth century on imported Asian chestnut trees. Japanese and Chinese chestnuts are resistant to the disease. While they can contract the disease, they don’t show the serious symptoms seen in American chestnuts. You might not even notice the infection unless you strip the bark from an Asian tree.
You might wonder why we don’t replace our American chestnuts with the resistant Asian varieties. The problem is that the Asian trees are not of the same quality. American chestnut trees were extremely important commercially because these fast-growing, tall, straight trees produced superior lumber and a bountiful harvest of nutritious nuts that were an important food for both livestock and humans. Asian trees can’t come close to matching the value of American chestnut trees.
Chestnut Blight Life Cycle
Infection occurs when spores land on a tree and penetrate the bark through insect wounds or other breaks in the bark. After the spores germinate, they form fruiting bodies which create more spores. The spores move to other parts of the tree and nearby trees with the help of water, wind, and animals. Spore germination and spread continue throughout spring and summer and into early autumn. The disease overwinters as mycelium threads in cracks and breaks in the bark. In spring, the entire process begins again.
Cankers develop at the site of infection and spread around the tree. The cankers prevent water from moving up the trunk and across the branches. This results in dieback from lack of moisture and the tree eventually dies. A stump with roots may survive and new sprouts may emerge, but they never survive to maturity.
Researchers are working to develop resistance to chestnut blight in trees. One approach is to create a hybrid with the superior characteristics of the American chestnut and the disease resistance of the Chinese chestnut. Another possibility is to create a genetically modified tree by inserting disease resistance into the DNA. We’ll never again have chestnut trees as strong and plentiful as they were in the early 1900s, but these two research plans give us reason to hope for a limited recovery.
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Read more about Chestnut Trees
Blight Resistant American Chestnut Trees
The American chestnut tree once dominated the landscape of the eastern U.S., from Mississippi to Maine. The tree grew straight and tall – over 100 feet – and was valued for its hardwood as well as its tasty nut. These forests were decimated by an Asian chestnut blight that struck the U.S. in 1904, but now scientists are getting close to producing healthy, fungus-resistant American chestnut trees through genetic engineering and careful cross-breeding. Growers in the American West, where stands of chestnuts were spared from the blight, are also working to establish blight-resistant chestnuts.
Written by: D. J. Moorhead, G. K. Douce, C. Evans, and D. Kennard for Forest Encyclopedia Network
Chestnut blight (Cryphonectria parasitica) has probably had the most pervasive influence on forest structure and composition in the southern Appalachians of any disease or insect. Prior to the introduction of this disease, the American chestnut (Castanea dentata) was the tallest and most dominant hardwood species in the eastern United States (Fig. 2). It grew in vast stands from Maine to Florida, with the largest trees occurring in the southern Appalachians (Schlarbaum et al. 1997). After the introduction of the fungus, which probably arrived on nursery stock from Asia around 1900, native chestnut trees, which had no resistance, quickly succumbed. The fungus enters a host through cracks or wounds in the bark and multiplies rapidly. It produces sunken cankers which expand and girdle the stem, killing everything above the canker, usually in one growing season (Fig. 1). Fungus spores can be transported by wind or on the feet of migrating birds and insects. The disease can spread rapidly — about 24 miles per year (Schlarbaum et al. 1997). By 1929, nearly all counties in the southern Appalachians were infested by about 1940, most of the standing chestnut trees were dead (SAMAB 1996).
The chestnut blight fungus kills the aboveground portion of trees but does not affect root systems which can resprout. Therefore, American chestnut persists throughout its former range as young sprouts growing in the understory. These sprouts generally live for five to 10 years before being reinfested and killed back by the blight. Often chestnut sprouts reach heights of 25 feet or more, but they rarely flower and bear fruit before dieback. Despite the persistence of sprouts, there is a gradual loss of this species and its genetic resource. Areas with extensive chestnut rootstocks can be identified, and silvicultural practices that favor its shade-intolerant regeneration should be employed to protect or enhance sprout survival.
Restoration of Chestnut
There have been two primary research approaches to restore chestnuts to American forests: the use of hypovirulent strains and breeding.
Hypovirulence is a virus disease that weakens and slows the chestnut blight virus. Hypovirulence allows a chestnut tree with no resistance to the blight to form slow-growing swollen cankers normally produced only on resistant trees. Scientists have been trying to manipulate hypovirulence to develop an economical biocontrol for blight. However, several obstacles to this approach exist, including: (1) the blight spreads very rapidly in nature, while hypovirulence spreads very slowly and (2) there are many types of virulent strains in the forest which resist transfer of the virus responsible for hypovirulence. Despite these limitations, hypovirulent strains have been used to bring about recovery from chestnut blight in certain situations (Scibilia and Shain 1989, Anagnostakis 1990, MacDonald and Fulbright 1991, Brewer 1995). For example, some positive results have been achieved by using molecular biology to transfer the debilitating genes of the virus into the fungus (Choi and Nuss 1992, Schlarbaum et al. 1997).
Two strategies have been pursued to breed a blight-resistant American chestnut: (1) breeding within the American chestnut gene pool and (2) hybridization with Asian chestnut species.
Breeding within American chestnut populations was begun with the occasional surviving trees that were thought to possess some resistance. Enzymatic studies of inner bark tissue revealed small resistance differences among trees (Samman and Barnett 1973, McCarroll and Thor 1985). Cross pollinations were made among putatively resistant trees, but resistance could not be increased to an acceptable level and the approach was abandoned (Thor 1978, Schlarbaum et al. 1997)
Resistance in Asian chestnut species, particularly Chinese chestnut (C. mollissima) and Japanese chestnut (C. crenata), was evident to scientists in the early 1900s (Fig. 3). Early breeding programs were initiated by state and federal agencies in the 1930s. However, the initial hybrids generated by these programs were not as blight resistant as the oriental chestnut parent. To increase resistance, these first hybrids were crossed back to a resistant oriental parent. Unfortunately, this strategy produced trees that were short and branching and not competitive in eastern forests (Schlarbaum et al. 1997). A number of breeding programs were more successful with the backcross method, which aimed to transfer blight resistance from Chinese chestnut to American chestnut while retaining the desirable growth, form, and adaptability of the American chestnut (Burnham et al. 1986, Burnham 1990). These trials produced two partially blight-resistant first backcrosses (BC1), the “Graves” tree and the “Clapper” tree, which were first-generation hybrids (Schlarbaum et al. 1997).
Although these early breeding programs did not produce a blight-resistant American chestnut, they left a valuable legacy of knowledge and germplasm. There is now evidence that only a few genes control blight resistance in Chinese chestnut, specifically two or three incompletely dominant genes. A genetic map of chestnut with regions associated with blight resistance was identified and could be used to screen newly germinated nuts for blight resistance. This process may enable several generations of backcrossing to be bypassed. The American Chestnut Foundation estimates that by 2012, nuts will be produced from the most blight-resistant breeding lines that can be used in reforestation (Schlarbaum et al. 1997).
Promising results have also been seen with an integrated management approach for American chestnut revival. This approach combines hypovirulence (by inoculation) with blight resistance (grafted). In Virginia’s Lesesne State Forest, trees grafted with blight-resistant strains and inoculated with hypovirulence have been thriving for 20 years, but they are surrounded by nonresistant chestnuts, which are continuously killed back by the blight.
Other Exotic Pests of Chestnut
Chestnut blight was actually preceded by another exotic fungal disease, Phytophthora cinnamomi, which infested southern populations of American chestnut and the related Allegheny chinkapin as early as 1824 (Crandall et al. 1945). This root rot disease constricted the natural range of chestnut to upland areas. On these upland sites, chestnuts are challenged by yet another exotic pest, the chestnut gall wasp (Dryocosmus kuriphilus) (Fig. 4). Chestnut gall wasp larvae feed upon bud and flower tissues, forming a characteristic gall and producing a toxin that can kill the infested branch. Infestations by this insect, which can cause tree mortality, were first reported in 1974 (Payne et al. 1975) and now have spread north into Tennessee and North Carolina (Schlarbaum et al. 1997).
Facts about Blight Resistance
American chestnut seedlings are usually highly susceptible to the blight. In older trees (more than 1.5 inches in diameter at breast height), a resistant individual can slow down progress of the disease and may survive in spite of blight, but it is not immune. Many kinds of environmental stress may break down a tree’s resistance to blight. Indeed, at high elevations in areas exposed to severe climate, normally resistant oriental chestnuts have been killed by blight.
Even where all the American chestnuts have been killed, the blight fungus is still present. Planting of so-called “blight-free” chestnuts has been widely publicized, but this practice is ineffective. “Blight free” merely means a tree is uninfected when grown in an area where no blight is present such as outside the natural range or inside a greenhouse. This is no guarantee that the tree will not contract blight in the future. Furthermore, this practice raises false hopes among the public and may discourage research funding (SAMAB 1996).
For more information on this disease, see Revitalization of the Majestic Chestnut: Chestnut Blight Disease at the American Pathological Society’s website.
Adapted for eXtension by Thomas DeGomez, University of Arizona
Identifying and Treating Chestnut Tree Diseases
Chestnuts are sturdy, pest-resistant trees and very few chestnut diseases can cause large-scale damage. Chestnut trees, part of the Castanea family, require little maintenance, pruning or fertilization. However, some weather conditions can make chestnuts vulnerable to fungal infections. These diseases are easy to detect, but can be hard to contain. You should know how to identify such diseases in their initial stage and prevent them from spreading.
Disease 1 - Chestnut Blight Disease
This is the most destructive of all known, chestnut diseases. There are no easy methods to cure a chestnut blight infection and most affected chestnuts eventually die. Also called the Bark Disease, it is caused by the Cryphonectria fungus. The fungus enters the tree’s bark through wounded sites on the bark’s surface.
Chestnut Blight Symptoms
The fungus causes quick deterioration in the overall health of the bark. Due to widespread tissue infection, small canker-like sores develop on the bark. The younger stems start thinning and branching, excessively. Small sprout-like bodies can be seen around the cankers. Within weeks of infection, the bark appears shrunk. The tree may even appear bent due to rapid loss of tissue from one side of the bark. Cankers caused by fungal infection often become the nesting ground for the Bark Miner. This insect usually doesn't attack healthy chestnuts but in diseased trees, it multiplies quickly. The presence of miner means intensive feeding and creation of more bruised sites on the bark. This further helps the spread of fungal infection among the upper branches of the tree.
Chestnut Blight Control
No effective form of organic or chemical control is known that can completely cure blight-affected chestnut trees. Most advocated treatments are very expensive and include the use of complex, scientific techniques. Therefore, making your chestnuts immune against blight infestation through the following two-fold strategy is recommended:
Before planting a chestnut, make some enquiries in your area. If the surrounding landscape has a history of chestnut blight infections, you should grow the Asiatic varieties, like Chinese chestnut. This chestnut is more resistant against fungal infections. When procuring a chestnut plant, ensure that you ask for a certificate from the seller stating that the plant is free of blight-causing pathogens. Most reputed garden supply stores issue such certificates.
You should guard against bruising the main bark. Never use heavy pruning shears for pruning chestnuts. Before pruning, dip your cutting equipment in an anti-fungal preparation. While pruning, ensure that you keep away from the main bark area. After pruning, check for wounded sites. Any kind of cut marks on the bark should be immediately sprayed with an all-purpose fungicide.
Oak mildew is the more serious form of powdery mildew that is commonly found in household gardens. It is also called the Chestnut Powdery Mildew. It is caused by the Sphaerotheca fungus.
Oak Mildew Symptoms
This disease is more common among the younger chestnuts. The shoots develop a dwarfed appearance. The tree becomes more sensitive to colder temperatures. The fungus is more developed along the upper half of leaves. The leaves develop a typical, white-colored, coated appearance. However, this coating can be seen during the summer season only.
Oak Mildew Control
Any part of the tree showing symptoms of mildew should be pruned-off. Chemical control is best suited for treating this disease. You can use any retailed fungicide that has sulphur and benomyl in the listed formulation. Repeated fungicide spraying is both curative and preventive. You should prune-off, curled-up branches to create entry points for air. Increased ventilation in the foliage helps to limit the spread of mildew.
Chestnut Blight Facts And Information: How To Prevent Chestnut Blight In Trees - garden
By Dr. Sandra L. Anagnostakis
Department of Plant Pathology and Ecology
The Connecticut Agricultural Experiment Station
123 Huntington Street
P. O. Box 1106
New Haven, CT 06504-1106
Telephone: (203) 974-8498 Fax: (203) 974-8502
Email: [email protected]
American chestnut trees (Castanea dentata) were once so common in the Eastern United States that everyone who could get to the woods in the fall could count on nuts for roasting and for stuffing their Thanksgiving turkey. The wood was highly resistant to rot, and used extensively for poles, fencing, and building materials. An "imported" fungus disease was discovered in New York City in 1904, and within 50 years it had changed the appearance of our Eastern forests. The fungus, Cryphonectria (formerly Endothia) parasitica, enters wounds, grows in and under the bark, and eventually kills the cambium all the way around the twig, branch, or trunk. Everything distal to this "canker" then dies, sprouts are formed, and the process starts all over again. The fungus does not enter the "root collar" at the base of the tree, so sprout clumps survive today that are the remnants of the original trees. From the earliest discovery of the disease attempts were made to control it, but nothing worked. A major forest tree was reduced to a multiple-stemmed shrub (1). In 1912 the Plant Quarantine Act was passed to reduce the chances of such a catastrophe happening again (12).
Where did the chestnut blight fungus come from, and when did it come to the United States?
After the blight fungus was discovered here, plant explorer Frank Meyer found that it was present in both China and Japan, and that Asian trees were often very resistant to the disease and showed few symptoms when infected (10,11). This was taken as proof that Asian trees imported into the United States had brought the blight with them.
G. H. Powell wrote in 1900 (9) that Japanese chestnut trees (Castanea crenata) were first imported in 1876 by nurseryman S. B. Parsons of Flushing, New York (in the New York City borough of Queens, at the western end of Long Island). These were widely distributed, and two of them were planted and still survive in southern Connecticut. In 1882, William Parry in New Jersey imported 1,000 grafted Japanese chestnut trees. In the West, Luther Burbank planted a box of seeds sent by his collector from Japan in 1886. He subsequently had over 10,000 bearing trees growing in his Santa Rosa, California, nursery. Three of Burbank's selections were sold to Judge Coe in Connecticut, and then to J. H. Hale who propagated and sold them from his South Glastonbury, Connecticut, nursery.
Powell also reported that (by 1899) there were over 300 acres of chestnut trees near Philadelphia grafted with European and Japanese varieties, and that the Lovett Co. in Little Silver, New Jersey, (near the coast, about 15 miles south of Long Island) had also imported Japanese chestnut trees and were selling them by mail-order.
The 1899 and 1900 catalogues of the Mt. Hope Nursery (also known as Ellwanger and Barry, Rochester, New York) advertised Japanese, European, and American chestnut trees for sale (Table 1). In 1930, when Arthur Graves was looking for resistant trees for breeding, he found large Japanese chestnut trees on several estates on Long Island (New York) and in northern New Jersey. He said that many of them had been purchased around the turn of the century as "Japanese Giant" from a nursery near Rochester (3).
Any, or many of these importations of Japanese chestnut trees could have been the source of chestnut blight. In addition, the mail-order sales could have spread imported blight to all of the places were the trees were shipped.
Chinese chestnut trees (Castanea mollissima) were imported later. G. D. Brill went to China in 1900 and sent back chestnuts from Hankow and Ichang, and Lathrop and Fairchild sent seed back from Canton in 1902. Most of these were planted in the seed nursery in Bell, Maryland, but may have been another source of blight for the South.
The discovery of chestnut blight in the Bronx Zoo was described by Merkel (4) as follows: ". a few scattered cases which occurred [on American chestnut trees] during the summer of 1904. Early last June  this disease was noticed on so many widely scattered trees of all sizes that specimen branches and an appeal for information were sent to the USDA".
W. A. Murrill reported in 1906 that: ". the disease is known to occur also in New Jersey, Maryland, the District of Columbia, and Virginia."
Then, in 1908 Murrill said: "The disease is abundant in and about New York City, on Long Island, and in New Jersey, and is known to occur along the Hudson as far north as Poughkeepsie. Specimens have been sent in from Connecticut, Massachusetts and Maryland.
The disease was at first supposed to be confined to our native chestnut, but in the autumn of 1906 an affected branch was found upon one of the Japanese chestnut trees (Castanea crenata) growing in the open near the eastern boundary of the [New York Botanical] Garden."
Later in 1908 Murrill wrote: "The origin of the disease and the center of its distribution are still entirely unknown, while the area of its distribution is known very imperfectly as yet and can be determined accurately only by careful field explorations conducted by competent persons."
A Pennsylvania Department of Forestry report by John Mickleborough (6) listed distribution in 1909: "Its presence is known by the writer from personal examinations to extend from near the northern boundary of Maryland, through south eastern Pennsylvania, across New Jersey and New York. . On Long Island the disease has spread for fifty or sixty miles with great rapidity, and is most prevalent and its ravages the most deadly. "
Since there was no blight in one area examined in Pennsylvania: "It was decided at once to make an Experiment Station at the Gap and to plant twenty-five Japanese chestnut trees and to start with one hundred grafts of the same species. . Through the generosity of Mr. Isaac Hicks, a nurseryman at Westbury, Long Island, twenty-five Japanese chestnut trees were donated for the experiment and all the Japanese scions that could be used," probably bringing the blight with them.
Finally, when Haven Metcalf and J. Franklin Collins wrote their 1909 Bulletin they stated: "Even [in 1904] it is certain that [chestnut blight] had spread over Nassau County and Greater New York, and had found lodgment in the adjacent counties of Connecticut and New Jersey. No earlier observation than this is recorded, but it is evident that the disease, which would of necessity have made slow advance at first, must have been in this general locality for a number of years in order to have gained such a foothold by 1904. Conspicuous as it is, it is strange that the fungus causing this disease was not observed or collected by any mycologist until May,1905, when specimens were received from New Jersey by Mrs. F. W. Patterson, the Mycologist of the Bureau of Plant Industry. . By August, 1907, specimens received by this Bureau showed that the disease had reached at least as far south as Trenton, N. J., and as far north as Poughkeepsie, N. Y., and was spread generally over Westchester and Nassau Counties, N. Y., Bergen County, N. J., and Fairfield County, Conn. . reports have been received from points as remote as Cape Cod, Wellesley and Pittsfield, Mass. Rochester and Shelter Island, N. Y., and Akron, Ohio. . It can be quite confidently stated that the bark disease does not yet occur south of Virginia.
The theory. that the Japanese chestnuts were the original source of infection, has been strengthened by many facts.
While the disease has spread principally from the vicinity of New York City] there is much to indicate that it occurred at other points at an early date. Chester's Cytospora on a Japanese chestnut noted at Newark, Del., in 1902, may have been the bark disease. Observations by the junior writer indicate that this disease may have been present in an orchard in Bedford County, Va. as early as 1903, and that in Lancaster County, Pa., it probably was present as early as 1905..
It becomes more and more evident as this disease is studied that diseased nursery stock is the most important factor in its spread to distant points."
Can we tell now where the chestnut blight fungus first came in?
Any or all of those early Japanese imports could have carried it. Certainly, the Bronx Zoo was not responsible for bringing it in, even though their sharp-eyed grounds people first recognized the problem. People anxious to plant something new and different do not always notice problems on old and common plants. The catastrophe crept up on us, and left us a lesson that we continue to try to cope with today.
A biological control imported from Europe in 1972 allows us to keep American chestnut trees alive for breeding, and may be improved for better spread in the forest (1). Breeding projects are underway to combine the nut quality and timber form of American chestnuts with blight resistance of Asian chestnuts to produce trees for orchards and forests. We cannot undo the mistake of bringing chestnut blight into the United States, but perhaps understanding the history of this catastrophe will make us more cautious in the future.
Table 1. Chestnut Trees by Mail Order Showing Catalog, Date, Species Sold and Cost.
Reading Nursery, Jacob W. Manning, MA 1900: American .50-1.00
J. T. Lovett Co. Little Silver, NJ 1888 : 'Japan Giant' .75 Spanish .30 American .10-0.25 'Numbo' .75
Storrs and Harrison, Painesville, OH 1888: American .50 'Japan Giant' .50-0.75 Spanish .50
Shady Hill Nursery F.L. Temple, Cambridge (Somerville), MA 1888/1889: American .10-0.35
Highlands Nursery, H. P. Kelsey, Boston, MA 1899/1900: American .25
Biltmore Nursery, Biltmore, NC 1900/1901: American .15-0.50
Mt. Hope Nursery, Ellwanger and Barry, Rochester, NY 1897: C. Americana .50 C. Japonica $1.00 C. vesca .50
Elm City Nursery, New Haven, CT 1901: American .50-1.00 Spanish .25-1.00 'Numbo' $1.50 Japanese .50-1.00
Fruitland Nurseries, P.J. Berckmans, Augusta, GA 1900: American .25-1.00 Spanish .25
Hale's Fruits, J.H. Hale, South Glastonbury, CT 1903: Japanese hybrids (from Luther Burbank) 'Coe', 'Hale', 'McFarland'
C.B. Hornor and Son, Mt. Holly, NJ 1897: American 0.$25-0.35 'Numbo' .75 'Paragon' $1.00-2.50
1. Anagnostakis, S. L. and B. Hillman. 1992. Evolution of the chestnut tree and its blight. Arnoldia 52:3-10.
2. Crane, H. L., C. A. Reed, and M. N. Wood. 1937. Nut Breeding (chestnut on pp. 827-835), Yearbook of Agriculture for 1937, pp. 827-889.
3. Graves, Arthur H. 1930. Progress toward the development of disease resistant strains of chestnut. Brooklyn Botanic Garden Record, 19:62-67.
4. Merkel, Hermann W. 1905. A deadly fungus on the American chestnut. N.Y. Zoological Society, 10th Annual Report, pp. 97-103.
5. Metcalf, Haven and J. Franklin Collins. 1909 The present status of the chestnut bark disease. USDA Bureau of Plant Industry Bulletin #141, part V.
6. Mickleborough, John. 1909. A report on the chestnut tree blight, the fungus Diaporthe parasitica, Murrill. Department of Forestry, The Commonwealth of Pennsylvania, Harrisburg.
7. Murrill, W. A. 1908a. The spread of the chestnut disease. Journal of the New York Botanical Garden 9:23-30.
8. Murrill, W. A. 1908b. The chestnut canker. Torreya 8:111-112.
9. Powell, G. H. 1900. The European and Japanese chestnuts in the Eastern United States. 11th Annual Report of the Delaware College Agricultural Experiment Station, pp. 101-135.
10. Shear, C. L. and N. E. Stevens 1913. The chestnut-blight parasite (Endothia parasitica) from China. Science 38:295-297.
11. Shear, C. L. and N. E. Stevens 1916. The discovery of the chestnut-blight parasite (Endothia parasitica) and other chestnut fungi in Japan. Science 43:173-176.
12. Waterworth, H. E. and G. A. White 1982. Plant introductions and quarantine: the need for both. Plant Disease 66:87-90.
The chestnut blight fungus was accidentally introduced into the U.S. on Japanese chestnut trees imported at the end of the 1800s. It was spread all over the range of our native chestnut trees by "mail order" as people bought chestnut trees from nurseries, and was spread locally by every creature that walked over the cankers. This led to the enactment of Plant Quarantine laws in the United States.
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What it Takes to Bring Back the Near Mythical American Chestnut Trees
Sometimes reaching a height of more than 100 feet tall with trunk diameters often well over 10 feet, the American chestnut was the giant of the eastern U.S. forests. There were once billions of them and their range stretched from Georgia and Alabama to Michigan, but the majestic tree was gone before forest science existed to document its role in the ecosystem.
Notes left by early foresters including Gifford Pinchot, the founder and first chief of the USDA Forest Service, suggest that its ecological role was as impressive as the tree’s size (PDF, 1.3 MB).
Mature American chestnuts have been virtually extinct for decades. The tree’s demise started with something called ink disease in the early 1800s, which steadily killed chestnut in the southern portion of its range. The final blow happened at the turn of the 20th century when a disease called chestnut blight swept through Eastern forests.
The disappearance of the chestnut launched a profound change in the structure and composition of eastern forests.
But, after decades of work breeding trees, The American Chestnut Foundation, a partner in the Forest Service’s effort to restore the tree, is close to being able to make a blight-resistant American chestnut available. However, the opportunity to restore the tree to its native range creates a question for scientists and foresters: What conditions are necessary for the American chestnut to grow and regenerate on a landscape scale?
Forest Service Research and Development scientists in the Southern Research Station and the Northern Research Station are partnering with national forests in the Southern and Eastern regions of the National Forest System to answer that question. Several studies are under way that are aimed at developing management protocols foresters can use to reintroduce the species to forests.
And hope is literally growing.
Several national forests in both regions have hosted experimental American chestnut plantings to assist in the development of reintroduction strategies. Managers on the Allegheny National Forest have demonstrated a deep commitment to chestnut restoration by explicitly including it as a goal in the forest’s Land and Resource Management Plan and establishing numerous chestnut plantations over the past 25 years.
In order to build on their goals, Allegheny National Forest managers and Northern Research Station scientists are collaborating in four new studies on the forest and surrounding forestlands to evaluate first the importance of site quality to chestnut competitive ability and blight resistance second the impact of deer browsing on chestnut survival and growth third the planted chestnut response to prescribed fire and fourth the application of the three-stage shelterwood system for chestnut establishment.
The end goal of this collaboration among scientists and foresters is that the integration of their research will yield a holistic set of tools for reintroducing an iconic and long-absent tree species to the region and once again restore the lost giant of the eastern forests.
History of chestnut blight in Victoria
Chestnut blight disease was first detected in the Ovens Valley in Victoria’s north-east in September 2010. Since this time, Agriculture Victoria has worked with affected growers and the national chestnut industry to eradicate the disease. Over 740,000 trees were inspected and over 5,000 diseased and at-risk chestnut trees have been removed.
Three new detections in 2017 triggered a review of the national chestnut blight response. Further surveillance conducted in 2018 and 2019 indicated that there were low levels of chestnut blight still present.
In October 2019, the National Management Group determined that chestnut blight was no longer feasible to eradicate from Australia because it can remain dormant for many years before symptoms become visible, making it very difficult to detect and eradicate. This shifted the response into a Transition to Management program.
The Transition to Management program (19 December 2019 — 18 December 2020) aims to transition the response to an effective and sustainable long-term management program with industry leadership, supported by Agriculture Victoria and the community.