Hypoxylon canker of shade trees

Last updated
Hypoxylon mammatum signs on aspen Hypoxylon mammatum signs on aspen.jpg
Hypoxylon mammatum signs on aspen

Hypoxylon canker of shade trees is a weak ascomycete fungus that negatively affects growth and can eventually lead to the death of weak or diseased host trees. [1] There are many different species that affect different trees. For example, Hypoxylon atropunctatum , a common species, is found on oak trees, Hypoxylon tinctor affects sycamore trees, and Hypoxylon mammatum infests aspen trees. [1] [2] [3]

Contents

Although the fungus is found on the majority of tree bark in an infested area, it only harms the tree when the tree becomes stressed or injured because it is easier to infect. [2] Thus, Hypoxylon had an endophytic stage. An endophyte is an organism such as a bacterium or fungus that spends some of its life not causing disease to the host while being on it. When a stress or injury occurs, the fungus will infect and begin living off the nutrients of the tree. Hypoxylon infects trees throughout the United States, but a few notable wide-scale problems have occurred in Arkansas, North Texas, Oklahoma, and the Mountain West. [1] [2] [3] [4]

Hypoxylon canker of shade trees is a secondary disease: a primary factor, such as drought or physical damage, usually causes the dying and decaying of the tree first before the Hypoxylon canker pathogen infects. [5] This will cause the tree to be in stress and potentially start to decay. The pathogen infects the living tree while it is in stress; it will not infect a tree that is healthy or already dead. [1] In order for a tree to become infected, the tree must be already dying or at least must have branches that are dying. The pathogen will therefore kill the tree if the tree is unhealthy.

Hosts and symptoms

Hypoxylon mammatum symptoms on aspen Hypoxylon mammatum symptoms on aspen.jpg
Hypoxylon mammatum symptoms on aspen

Hypoxylon canker of shade trees has three primary species, through which the pathogen can infect a variety of hardwood shade trees. Hypoxylon atropunctatum is most commonly found on oak, Hypoxylon mammatum is a significant pathogen on aspen trees, and Hypoxylon tinctor infects sycamore trees. [1] [2] [3] In order to tell if the pathogen is affecting the tree, the bark must be closely examined, but the symptoms are distinct.

Early stages of the disease show a light brown and tan color that looks dry and dusty. Later on, as the pathogen goes through the sexual stage, the bark will turn to a dark grey color. The bark becomes brittle and flakes off, [2] and black and grey cankers will appear. [1] These changes are symptoms, indications of a disease. They demonstrate that the pathogen is present and infecting or has already infested the host.

Hypoxylon also produces characteristic signs, which are either going to be direct products of the pathogen or the appearance of the pathogen itself. The visible signs from Hypoxylon are conidia and ascospores. Conidia are produced during the asexual stage, while ascospores are produced during the sexual stage. [5] [6] One can sometimes see the conidia with the naked eye if they are structuralized, but it is much easier to see them under a dissecting microscope. When looking through a compound microscope, it is possible to see the ascospores. They will be located on perithecia. The microscopic signs of the perithecium are the flask-shaped sexual fruiting body that contains ascospores.

Lastly, the pathogen is going to be found primarily just beneath the bark of the trees, located throughout the tree and if the pathogen spreads. The pathogen can also spread to the bark of surrounding trees. [1] If one sees symptoms on the main trunk, the tree is likely too diseased to save, since the trunk is the spot where the nutrients and water are transported. Once Hypoxylon is active on the main trunk, there is no other way for the water and nutrients to get to the rest of the tree and thus it dies. Fortunately, if Hypoxylon is found on the branches or limbs there is a good chance the tree will live if the fungus does not spread. Pruning out the limbs and branches that look like they have the disease on it or are dying will solve the problem. [2]

Disease cycle

Factors that give rise to infection

Hypoxylon canker of shade trees is an ascomycete fungal disease. [7] [8] The fungal pathogen must take advantage of wounds in the host tree or unhealthy tree tissue to infect and colonize the host, as normal, robust trees are not very susceptible to infection. [7] However, many hosts of Hypoxylon canker, such as red and post oaks, are especially sensitive to external factors; thus, they are easily stressed and can become susceptible hosts. [2] It is often noted that Hypoxylon canker does not kill a tree—it merely capitalizes on trees that are already dying due to stress or other means, and may be a significant contributing factor to tree death. [1] It is important to note that the Hypoxylon can remain dormant in healthy trees for many years before becoming pathogenic due to plant stress from temperature, water loss, physical and chemical diseases, and other plant pathogens. [4]

Stages of infection

While the spores can colonize and slowly grow under the bark of trees in an endophytic stage, they do not demonstrate any pathogenic effects or grow in great numbers until the tree is water stressed, nutrient depleted, or physically damaged; for this reason, the year following a significant drought or other physical stress is often when Hypoxylon canker is seen in shade trees. [5] Thus, before stress, Hypoxylon only infects its host in a local, benign manner, with limited propagation. Once the stress occurs, however, the fungus colonizes the inner parts of the bark and vascular system; while the infection is not fully systemic, it is certainly less localized than before stress. [5] Hypoxylon canker of shade trees has both an asexual (anamorph) and sexual (teleomorph) life cycle. [2]

Asexual (anamorph) stage

The fungus can infect seedlings and typically colonizes under the bark of the trees. [1] Since the fungus infects under the bark, the signs of the pathogen aren't visible until the bark sheds off in response to the physical pressure imposed by the growthing pathogen; this typically happens in the transition between spring and summer. [1] This shedding reveals large brown fungal mats, called stroma, which are the asexual reproductive structures that house the asexual spores, conidia, on conidiophores. [5] At this point, the reproductive structures will release conidia. [1] These spores are distributed by wind or rain splash. [1] If these spores land on a susceptible host, successful infection will take place if there are humid and warm conditions for 48 hours. [7]

Sexual (teleomorph) stage

After the conidia have been dispersed by late summer and fall, the stroma turn very dark, often brown or black, and crusty. [1] At this point, the stroma produce sexual fruiting bodies. Within these perithecia fruiting bodies, the sexual spores—ascospores—are produced in and can also be distributed via rain splash and wind and infect in a manner similar to the conidia. [6] [9]

Environment

Hypoxylon canker greatly depends on dying tree matter, which is why it generally attacks only damaged and stressed trees. Normal, healthy trees are able to fend off infection with their natural defense mechanisms such as basal defense and hypersensitive response. [2] Furthermore, it is known that the Hypoxylon fungi already exist on the majority of trees and are only waiting for a possible infection route to be created. When damage or stress occurs, the fungi will further colonize, infect, and begin living off the nutrients of the tree, flourishing in the bark and vascular system. [2] Natural stresses such as defoliation by insects, animal damage, soil nutrient depletions, drought, overcrowding, and other disease can weaken trees, enabling Hypoxylon to infect. [10] Human-caused problems can also lead to infection; soil compaction and excavation, construction, and physical injuries are known stresses to trees. [10]

Drought is one of the major indicators that Hypoxylon will become a problem in the following months to years. Droughts account for a large majority of tree-related problems as the water deficit has a negative effect on the tree's natural developments. [10] Symptoms usually develop within a year after a drought, but with extreme conditions can develop in a matter of months. [5] A major factor in the survival of Hypoxylon canker is the moisture content within the tree wood. When the stresses mentioned above begin to weaken the tree, moisture content of the wood decreases. As the wood further dries, the Hypoxylon fungi will feed and further white rot and decay of the tree will occur, potentially causing death. [10]

Management

Although there is no known cure for Hypoxylon canker, proper management practices and care can significantly reduce problems that may occur. Generally, avoiding tree stress and maintaining an overall healthy tree is the most ideal way of avoiding the canker. Avoiding any physical injuries to the trunk, limbs, or roots is important as these injuries can disrupt growth processes and xylem/phloem transport. Disruptions to the soil surrounding the tree should also be minimized. Any major disruptions, such as landscaping or irrigation modifications, in the surrounding environment can develop significant problems for both young and mature trees. [2] Proper herbicides, pesticides, and fertilizers should be used in further tree protection. Additionally, adequate propagation along with good drainage is extremely important in sustaining a healthy tree.

Studies have found that Hypoxylon canker favors lower tree density stands in addition to only stressed trees. [11] This could be due to the mode of spore dispersal, the inability of spores to germinate on older bark, the fungal method of entry, and the specific tree age. [12] If possible, minimize forest thinning unless recommended by an arborist or qualified specialist.

When dead or dying tree branches do appear, selective pruning should be performed to remove these potential infection sources. The removal of dead or infected regions can prevent or considerably reduce advances of Hypoxylon. [1]

Importance

The most significant impact of Hypoxylon canker of shade trees is that the ascomycete fungal pathogen can contribute to the death of many species of tall, mature shade trees. [5] This can have an economic impact, since many of these types of trees are used for aesthetic landscaping in residential and commercial areas. [7]

There is also an ecological impact; specifically, Hypoxylon canker is most devastating to forest aspen trees. [7] Aspen distribution in Utah, in National Forest System lands, has decreased by 60%. [13] Though Hypoxylon is not the major cause of this decline, Hypoxylon mammatum is estimated to infect 30% of aspens each year across the Midwest. [3] In 1972, the damage was significant enough to cause losses of $4 million worth of aspen across Wisconsin, Minnesota, and Michigan. [3] Furthermore, severe drought conditions throughout the American West could exacerbate Hypoxylon damage to aspens since the fungus takes advantage of water stressed trees. [14]

Overall, the loss of aspen or any other species of tall, mature shade trees can have a large impact on the surrounding ecosystem; these trees can serve as habitat for a variety of animals. [4] Since Hypoxylon canker of shade trees is found throughout the United States, in regions such as the mountain West, coastal South, and Midwest/Great Lakes region, [4] [7] [13] the preservation and protection of the host trees is particularly significant.

Related Research Articles

<span class="mw-page-title-main">Chestnut blight</span> Fungus disease of chestnut trees

The pathogenic fungus Cryphonectria parasitica is a member of the Ascomycota. This necrotrophic fungus is native to East Asia and South East Asia and was introduced into Europe and North America in the early 1900s. The fungus spread rapidly and caused significant tree loss in both regions.

<i>Aspergillus flavus</i> Species of fungus

Aspergillus flavus is a saprotrophic and pathogenic fungus with a cosmopolitan distribution. It is best known for its colonization of cereal grains, legumes, and tree nuts. Postharvest rot typically develops during harvest, storage, and/or transit. Its specific name flavus derives from the Latin meaning yellow, a reference to the frequently observed colour of the spores. A. flavus infections can occur while hosts are still in the field (preharvest), but often show no symptoms (dormancy) until postharvest storage or transport.

<span class="mw-page-title-main">Oak wilt</span> Plant disease

Oak wilt is a fungal disease caused by the organism Bretziella fagacearum that threatens Quercus spp. The disease is limited to the eastern half of the United States; first described in the 1940s in the Upper Mississippi River Valley. The pathogen penetrates xylem tissue, preventing water transport and causing disease symptoms. Symptoms generally consist of leaf discoloration, wilt, defoliation, and death. The disease is dispersed by insect vectors and to adjacent trees through underground root networks. However, human spread is the most consequential dispersal method. Moving firewood long distances can potentially transport diseases and invasive species.

<span class="mw-page-title-main">Diplodia tip blight</span> Fungal disease of conifers

Diplodia tip blight, also known as Sphaeropsis blight, is a widespread disease affecting conifers caused by an opportunistic fungal pathogen, Diplodia sapinea. It is found in “both hemispheres between the latitudes 30° and 50° north and south". The diseases symptoms include: damping off and collar rot of seedlings, stem canker, root disease, and, most commonly, shoot blight. These symptoms have caused significant economic loss to nurseries and pine plantations. In a nursery in the north-central United States, losses of 35% have been reported. Shoot blight and eventual die back can cause a reduction of marketable volume in timber by 63%. Infection of terminal shoots can result in dead-top which significantly limits the usable length of the tree trunk. The presence of the pathogen in concert with severe weather conditions can lead to extreme loss. Following a severe hailstorm in South Africa, nearly 5,000 acres of pine plantation were infected with Diplodia tip blight. It was necessary to prematurely harvest large swaths of the plantations resulting in a loss of 45%. Areas that were not harvested prematurely still suffered an average timber loss of 11%.

<i>Ophiostoma ulmi</i> Species of fungus

Ophiostoma ulmi is a species of fungus in the family Ophiostomataceae. It is one of the causative agents of Dutch elm disease. It was first described under the name Graphium ulmi, and later transferred to the genus Ophiostoma.

<i>Monilinia fructicola</i> Species of fungus

Monilinia fructicola is a species of fungus in the order Helotiales. A plant pathogen, it is the causal agent of brown rot of stone fruits.

<i>Botryosphaeria dothidea</i> Species of fungus

Botryosphaeria dothidea is a plant pathogen that causes the formation of cankers on a wide variety of tree and shrub species. It has been reported on several hundred plant hosts and on all continents except Antarctica. B. dothidea was redefined in 2004, and some reports of its host range from prior to that time likely include species that have since been placed in another genus. Even so, B. dothidea has since been identified on a number of woody plants—including grape, mango, olive, eucalyptus, maple, and oak, among others—and is still expected to have a broad geographical distribution. While it is best known as a pathogen, the species has also been identified as an endophyte, existing in association with plant tissues on which disease symptoms were not observed. It can colonize some fruits, in addition to woody tissues.

Leptosphaeria coniothyrium is a plant pathogen. It can be found around the world.

<i>Nectria cinnabarina</i> Fungal plant pathogen

Nectria cinnabarina, also known as coral spot, is a plant pathogen that causes cankers on broadleaf trees. This disease is polycyclic and infects trees in the cool temperate regions of the Northern Hemisphere. N. cinnabarina is typically saprophytic, but will act as a weak parasite if presented with an opportunity via wounds in the tree or other stressors that weaken the tree's defense to the disease. A study published in 2011 showed that this complex consists of at least 4 distinct species. There are only a few ways to manage this disease with techniques such as sanitation and pruning away branches that have the cankers. N. cinnabarina is not as significant a problem as other Nectria spp., some of which are the most important pathogens to infect hardwood trees.

<i>Botryosphaeria ribis</i> Species of fungus

Botryosphaeria ribis is a fungal plant pathogen that infects many trees causing cankers, dieback and death.

<i>Diaporthe helianthi</i> Species of fungus

Diaporthe helianthi is a fungal pathogen that causes Phomopsis stem canker of sunflowers. In sunflowers, Phomopsis helianthi is the causative agent behind stem canker. Its primary symptom is the production of large canker lesions on the stems of sunflower plants. These lesions can eventually lead to lodging and plant death. This disease has been shown to be particularly devastating in southern and eastern regions of Europe, although it can also be found in the United States and Australia. While cultural control practices are the primary method of controlling for Stem Canker, there have been a few resistant cultivars developed in regions of Europe where the disease is most severe.

The plant pathogenic fungus Leucostoma kunzei is the causal agent of Leucostoma canker, a disease of spruce trees found in the Northern Hemisphere, predominantly on Norway spruce and Colorado blue spruce. This disease is one of the most common and detrimental stem diseases of Picea species in the northeastern United States, yet it also affects other coniferous species. Rarely does it kill its host tree; however, the disease does disfigure by killing host branches and causing resin exudation from perennial lesions on branches or trunks.

Eutypella canker is a plant disease caused by the fungal pathogen Eutypella parasitica. This disease is capable of infecting many species of maple trees and produces a large, distinguishable canker on the main trunk of the tree. Infection and spread of the disease is accomplished with the release of ascospores from perithecia. Therefore, the best way to manage the Eutypella canker is to remove trees that have been infected. If infected, it can decrease the quality of wood cut for lumber and can thus have a negative economic impact.

<i>Ceratocystis coerulescens</i> Species of fungus

Ceratocystis coerulescens is an ascomycete fungus and the causal agent of sapstreak disease in sugar maple trees. There is debate about whether it is one species or two; the second being Ceratocystis virescens. For simplicity, this page will refer to this pathogen as one species. It is also known by its anamorph name Endoconidiophora virescens.

<i>Dibotryon morbosum</i> Species of fungus

Dibotryon morbosum or Apiosporina morbosa is a plant pathogen, which is the causal agent of black knot. It affects members of the Prunus genus such as; cherry, plum, apricot, and chokecherry trees in North America. The disease produces rough, black growths that encircle and kill the infested parts, and provide habitat for insects.

<i>Armillaria</i> root rot Fungal tree disease

Armillaria root rot is a fungal root rot caused by several different members of the genus Armillaria. The symptoms are variable depending on the host infected, ranging from stunted leaves to chlorotic needles and dieback of twigs and branches. However, all infected hosts display symptoms characteristic of being infected by a white rotting fungus. The most effective ways of management focus on limiting the spread of the fungus, planting resistant species, and removing infected material. This disease poses a threat to the lumber industry as well as affecting recreational areas.

<i>Fusarium circinatum</i> Species of fungus

Fusarium circinatum is a fungal plant pathogen that causes the serious disease pitch canker on pine trees and Douglas firs. The most common hosts of the pathogen include slash pine, loblolly pine, Monterey pine, Mexican weeping pine, and Douglas fir. Like other Fusarium species in the phylum Ascomycota, it is the asexual reproductive state of the fungus and has a teleomorph, Gibberella circinata.

<span class="mw-page-title-main">Leucostoma canker</span> Plant fungal disease

Leucostoma canker is a fungal disease that can kill stone fruit. The disease is caused by the plant pathogens Leucostoma persoonii and Leucostoma cinctum (teleomorph) and Cytospora leucostoma and Cytospora cincta (anamorphs). The disease can have a variety of signs and symptoms depending on the part of the tree infected. One of the most lethal symptoms of the disease are the Leucostoma cankers. The severity of the Leucostoma cankers is dependent on the part of the plant infected. The fungus infects through injured, dying or dead tissues of the trees. Disease management can consist of cultural management practices such as pruning, late season fertilizers or chemical management through measures such as insect control. Leucostoma canker of stone fruit can cause significant economic losses due to reduced fruit production or disease management practices. It is one of the most important diseases of stone fruit trees all over the world.

Gummy stem blight is a cucurbit-rot disease caused by the fungal plant pathogen Didymella bryoniae. Gummy stem blight can affect a host at any stage of growth in its development and affects all parts of the host including leaves, stems and fruits. Symptoms generally consist of circular dark tan lesions that blight the leaf, water soaked leaves, stem cankers, and gummy brown ooze that exudes from cankers, giving it the name gummy stem blight. Gummy stem blight reduces yields of edible cucurbits by devastating the vines and leaves and rotting the fruits. There are various methods to control gummy stem blight, including use of treated seed, crop rotation, using preventative fungicides, eradication of diseased material, and deep plowing previous debris.

The foamy bark canker is a disease affecting oak trees in California caused by the fungus Geosmithia sp. #41 and spread by the Western oak bark beetle. This disease is only seen through the symbiosis of the bark beetles and the fungal pathogen. The bark beetles target oak trees and bore holes through the peridermal tissues, making tunnels within the phloem. The fungal spores are brought into these tunnels by the beetles and begin to colonize the damaged cells inside the tunnels. Symptoms of the developing fungus include wet discoloration seeping from the beetle entry holes as the fungus begins to consume phloem and likely other tissues. If bark is removed, necrosis of the phloem can be observed surrounding the entry hole(s). As the disease progresses, a reddish sap and foamy liquid oozes from entry holes, thus giving the disease the name foamy bark canker. Eventually, after the disease has progressed, the tree dies. This disease is important because of its detrimental effects on oak trees and its ability to spread to several new Californian counties in just a couple of years.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Vann, Stephen (2013). "Hypoxylon canker of hardwood shade trees" (PDF). www.uaex.uada.edu. University of Arkansas Cooperative Extension Service.
  2. 1 2 3 4 5 6 7 8 9 10 11 "Hypoxylon canker in shade trees". www.arborilogical.com. Arborilogical Services, Inc. Archived from the original on 26 June 2011.
  3. 1 2 3 4 5 Anderson, Ralph L.; Anderson, Gerald W.; Schipper, Jr., Arthur L. (October 1979). "Hypoxylon canker of aspen (Forest insect & disease leaflet 6)" (PDF). www.fs.usda.gov. USDA Forest Service.
  4. 1 2 3 4 Olson, Jennifer (May 2020). "Biscogniauxia (Hypoxylon) canker and dieback of trees". extension.okstate.edu. Oklahoma Cooperative Extension Service.
  5. 1 2 3 4 5 6 7 Blaedow, Ryan A. (August 2013). "The North Carolina Forest Service Forest Health Handbook, 3rd Edition" (PDF). www.ncforestservice.gov. North Carolina Forest Service.
  6. 1 2 Wood, Francis A.; French, D. W. (September 1965). "Microorganisms associated with Hypoxylon pruinatum". Mycologia . 57 (5): 766–775. doi:10.1080/00275514.1965.12018264. JSTOR   3757013.
  7. 1 2 3 4 5 6 Koetter, Rebecca; Grabowski, Michelle (2014). "Hypoxylon canker". extension.umn.edu.
  8. ↑ Bagga, Davinderjit K.; Smalley, Eugene B. (1974). "The development of Hypoxylon canker of Populus tremuloides: role of interacting environmental factors" (PDF). Phytopathology . 64 (5): 658–662. doi:10.1094/Phyto-64-658.
  9. ↑ "Hypoxylon canker and oaks". easttexasgardening.tamu.edu. Texas A&M AgriLife Extension Service. Archived from the original on 21 February 2015.
  10. 1 2 3 4 "Hypoxylon canker". texasforestservice.tamu.edu. Texas A&M Forest Service. Archived from the original on 21 August 2008.
  11. ↑ Anderson, Gerald W.; Anderson, Ralph L. (March 1968). "Relationship between density of quaking aspen and incidence of Hypoxylon canker". Forest Science . 14 (1): 107–112. doi:10.1093/forestscience/14.1.107 (inactive 2024-09-19).{{cite journal}}: CS1 maint: DOI inactive as of September 2024 (link)
  12. ↑ Schreiner, E. J. (September 1925). "Preliminary survey of Hypoxylon poplar canker in Oxford County, Maine". Mycologia . 17 (5): 218–220. doi:10.2307/3753778. JSTOR   3753778.
  13. 1 2 Bartos, Dale L.; Campbell, Robert B. (1998). "Decline of quaking aspen in the interior West—examples from Utah". Rangelands. 20 (1): 17–24.
  14. ↑ "Severe drought is causing the Western U.S. to rise". scripps.ucsd.edu. Scripps Institution of Oceanography. 21 August 2014.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.