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m Added that the disease was spotted in Southern Ontario (https://www.ontario.ca/page/oak-wilt#:~:text=Oak%20wilt%20is%20an%20introduced,Falls%20area%20of%20Southern%20Ontario.)
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{{short description|Plant disease}}
{{short description|Plant disease}}
{{Use dmy dates|date=June 2021}}
{{Infobox plant disease
{{Infobox plant disease
| name = Oak wilt
| name = Oak wilt
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| causal_agents = ''Bretziella fagacearum''
| causal_agents = ''Bretziella fagacearum''
| hosts = [[Oak|''Quercus'' spp.]]
| hosts = [[Oak|''Quercus'' spp.]]
| vectors = [[Nitidulidae|''Nitidulidae'']]
| vectors = ''[[Nitidulidae]]''
| EPPO_code = CERAFA
| EPPO_code = CERAFA
| second_EPPO_code =
| second_EPPO_code =
| distribution = USA
| distribution = US
| symptoms = leaf discoloration, wilt, defoliation and death
| symptoms = leaf discoloration, wilt, defoliation and death
| treatment =
| treatment =
}}
}}
{{speciesbox
{{taxobox
| name = ''Bretziella fagacearum''
| name = ''Bretziella fagacearum''
| image = Ceratocystis fagacearum endoconidia.jpg
| image = Ceratocystis fagacearum endoconidia.jpg
| image_caption = Spores produced by the oak wilt fungus (a) Endoconidia (b) Conidiophore
| image_caption = Spores produced by the oak wilt fungus (a) Endoconidia (b) Conidiophore
| regnum = [[Fungi]]
| taxon = Bretziella fagacearum
⚫
| authority = (Bretz) Z.W. de Beer, Marincowitz, T.A. Duong & M.J. Wingfield<ref name = EPPO1 />
| divisio = [[Ascomycota]]
| subdivisio = [[Pezizomycotina]]
| classis = [[Sordariomycetes]]
| subclassis = [[Hypocreomycetidae]]
| ordo = [[Microascales]]
| familia = [[Ceratocystidaceae]]
| genus = [[Bretziella]]
| species = '''''B. fagacearum'''''
| binomial = ''Bretziella fagacearum''<ref name = Myco1 />
⚫
| binomial_authority = (Bretz) Z.W. de Beer, Marincowitz, T.A. Duong & M.J. Wingfield <ref name = EPPO1 />
| range_map = OakWilt2017Counties.pdf
| range_map = OakWilt2017Counties.pdf
| range_map_caption = USA counties with oak wilt (2017)
| range_map_caption = USA counties with oak wilt (2017)
|synonyms =
| synonyms =
* ''Chalara quercina''<ref name = Myco1/>
* ''Chalara quercina''<ref name = Myco1/>
* ''Endoconidiophora fagacearum''
* ''Endoconidiophora fagacearum''
*''Thielaviopsis quercina''
*''Thielaviopsis quercina''
*''Ceratocystis fagacearum''<ref name = Com1/>
*''Ceratocystis fagacearum''<ref name = Com1/><ref name="Species Fungorum"/>
}}
}}
⚫
'''Oak wilt''' is a [[fungal]] [[disease]] caused by the [[organism]] ''Bretziella fagacearum'' that threatens [[oak|''Quercus'' spp.]]<ref name = Com1 /> The disease is limited to the [[Midwestern United States| Midwestern]] and [[Eastern United States]]; first described in the 1940's in the [[Upper Mississippi River| Upper Mississippi River Valley]]. The [[Plant pathology| pathogen]] penetrates [[xylem]] tissue, preventing water transport and causing disease symptoms.<ref name = mort1 /> Symptoms generally consist of leaf [[Chlorosis| discoloration]], [[Wilting |wilt]], [[Defoliant| 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.<ref name = SAF2/> Moving [https://www.dontmovefirewood.org/ firewood] long distances can potentially transport diseases and [https://www.playcleango.org/help-stop-invasive-species-with-playcleango invasive species].


⚫
'''Oak wilt''' is a [[fungal]] disease caused by the [[organism]] '''''Bretziella fagacearum''''' that threatens [[oak|''Quercus'' spp.]]<ref name = Com1 /> The disease is limited to the eastern half of the United States, and Southern Ontario. First described in the 1940s in the [[Upper Mississippi River| Upper Mississippi River Valley]]. The [[Plant pathology|pathogen]] penetrates [[xylem]] tissue, preventing water transport and causing disease symptoms.<ref name = mort1 /> Symptoms generally consist of leaf [[Chlorosis|discoloration]], [[Wilting|wilt]], [[Defoliant|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.<ref name = SAF2/> Moving firewood long distances can potentially transport diseases and invasive species.
⚫
=Disease=

⚫
== Disease ==
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Oak wilt is a devastating exotic disease, killing some trees rapidly in a single [[season]].<ref name = YT1/> Oak wilt is an important disease in [[urban areas]] where trees are highly valued. The disease reduces [[Real estate appraisal| property value]]s because of the loss of trees and is economically costly to the [[Title (property)|property owner]] since they or the local government must pay for [[Arboriculture| tree removal]]. Additionally, preventing the spread of the disease to [[Tree care| healthy trees]] is costly and requires vigilance. Oak wilt is also an important disease in a [[forest]] setting, as entire [[forest stand| forest stands]] can die within a few years.<ref name = PNAS2/> There is a narrow window to [[Salvage logging| salvage]] diseased trees for [[hardwood]] [[lumber]] and often the disease is not discovered within that [[logging]] window.<ref name = Eco2/> The [[Forest ecology| ecological]] impacts to forests is also a concern. The disease is currently restricted to North America, but is potentially a serious threat to oaks worldwide.<ref name = UK1/>
Oak wilt is a devastating exotic disease, killing some trees rapidly in a single season.<ref name = YT1/> Oak wilt is an important disease in [[urban areas]] where trees are highly valued. The disease reduces [[Real estate appraisal|property value]]s because of the loss of trees and is economically costly to the [[Title (property)|property owner]] since they or the local government must pay for [[Arboriculture|tree removal]]. Additionally, preventing the spread of the disease to [[Tree care|healthy trees]] is costly and requires vigilance. Oak wilt is also an important disease in a forest setting, as entire [[forest stand]]s can die within a few years.<ref name = PNAS2/> There is a narrow window to [[Salvage logging|salvage]] diseased trees for [[hardwood]] [[lumber]] and often the disease is not discovered within that logging window.<ref name = Eco2/> The [[Forest ecology|ecological]] impacts to forests is also a concern. The disease is currently restricted to North America, but is potentially a serious threat to oaks worldwide.<ref name = UK1/>


All [[oak|''Quercus'' spp.]] appear susceptible to the disease, with 33 oak species confirmed to be susceptible; including three species of ''[[Chestnut| Castanea]]'', one species of ''[[Castanopsis]]'', one species of ''[[Lithocarpus]]'', and some oaks native to Europe ([[Quercus petraea|''Q. petraea'']], [[Quercus pubescens|''Q. pubescens'']], & [[Quercus robur|''Q. robur'']]).<ref name = urban2/><ref name = IOS1/> Generally, red oaks ([[List_of_Quercus_species#Section_Lobatae|subsection ''Lobatae'']]) display more severe symptoms with rapid and frequent [[Mortality rate|mortality]] (particularily [[Quercus velutina|''Q. velutina'']], [[Quercus rubra|''Q. rubra'']], [[Quercus ellipsoidalis|''Q. ellipsoidalis'']] & [[Quercus coccinea|''Q. coccinea'']]). White oaks ([[List_of_Quercus_species#Section_Quercus|subsection ''Quercus'']]) develop symptoms more slowly, rarely die, and can recover from the pathogen with damage limited to a few branches (particularily [[Quercus alba|''Q. alba'']], & [[Quercus macrocarpa|''Q. macrocarpa'']]). [[Live oaks]] ([[Quercus fusiformis|''Q. fusiformis'']] & [[Quercus virginiana|''Q. virginiana'']]) display intermediate symptoms compared to red or white oaks. However, live oaks are semi-evergreen, can propagate vegetatively by root [[Basal shoot|suckering]], and cohabitate with other live oaks in dense [[forest stand|stands]] enabling interconnected root systems. These traits are favorable for local spread of the disease in an [[Central forest–grasslands transition| oak-grassland savanna]].<ref name = path2/>
All [[oak|''Quercus'' spp.]] appear susceptible to the disease, with 33 oak species confirmed to be susceptible; including three species of '' [[Chestnut|Castanea]]'', one species of ''[[Castanopsis]]'', one species of ''[[Lithocarpus]]'', and some oaks native to Europe ([[Quercus petraea|''Q. petraea'']], [[Quercus pubescens|''Q. pubescens'']], & [[Quercus robur|''Q. robur'']]).<ref name = urban2/><ref name = IOS1/> Generally, red oaks ([[List of Quercus species#Section Lobatae|subsection ''Lobatae'']]) display more severe symptoms with rapid and frequent [[Mortality rate|mortality]] (particularly [[Quercus velutina|''Q. velutina'']], [[Quercus rubra|''Q. rubra'']], [[Quercus ellipsoidalis|''Q. ellipsoidalis'']] & [[Quercus coccinea|''Q. coccinea'']]). White oaks ([[List of Quercus species#Section Quercus|subsection ''Quercus'']]) develop symptoms more slowly, rarely die, and can recover from the pathogen with damage limited to a few branches (particularly [[Quercus alba|''Q. alba'']], & [[Quercus macrocarpa|''Q. macrocarpa'']]). [[Live oaks]] ([[Quercus fusiformis|''Q. fusiformis'']] & [[Quercus virginiana|''Q. virginiana'']]) display intermediate symptoms compared to red or white oaks. However, live oaks are semi-evergreen, can propagate vegetatively by root [[Basal shoot|suckering]], and cohabitate with other live oaks in dense [[forest stand|stands]] enabling interconnected root systems. These traits are favorable for local spread of the disease in an [[Central forest–grasslands transition|oak-grassland savanna]].<ref name = path2/>


==History==
=== History ===
Oak wilt is one of [[Forest disturbance by invasive insects and diseases in the United States|three devastating North American]] vascular [[Wilt disease| wilt diseases]] that appeared in the early [[20th century]]. The other two vascular wilts are [[chestnut blight]] (1900-1950) and [[Dutch elm disease]] (1928 - 1980). Each of these non-native diseases have depopulated their respective host tree populations. [[Chestnut]] trees were the dominant [[Canopy (biology)|overstory]] tree species before chestnut blight and [[elms]] were an iconic [[Urban forestry| landscape]] tree that bordered streets before Dutch elm disease. Oak wilt and the newly emerging [[emerald ash borer]] have the potential to devastate other important North American tree species with large geographical and cultural significance. Range expansion of oak wilt to the [[Western United States]] (or to other [[continents]]) is a major concern.
Oak wilt is one of [[Forest disturbance by invasive insects and diseases in the United States|three devastating North American]] vascular [[wilt disease]]s that appeared in the early 20th century. The other two vascular wilts are [[chestnut blight]] (1900–1950) and [[Dutch elm disease]] (1928–1980). Each of these diseases have depopulated their respective host tree populations. [[Chestnut]] trees were the dominant [[Canopy (biology)|overstory]] tree species before chestnut blight and [[elm]]s were an iconic [[Urban forestry|landscape]] tree that bordered streets before Dutch elm disease. Oak wilt and the newly emerging [[emerald ash borer]] have the potential to devastate other important North American tree species with large geographical and cultural significance. Range expansion of oak wilt to the Western United States (or to other [[continents]]) is a major concern.


The asexual stage of oak wilt was first described in 1942 in Wisconsin.<ref name = henry/><ref name = bretz/> Soon thereafter the disease was reported throughout the [[Upper Midwest forest–savanna transition|Upper Midwest]] and [[Central forest–grasslands transition|Central]] forests. The early [[History_of_the_lumber_industry_in_the_United_States#Twentieth_century|20th Century]] coincided with oak regeneration after significant [[logging]] in the [[Mid-Atlantic (United States)|Mid-Atlantic]] and [[Great Lakes region]]. [[Deforestation in the United States|Deforestation]] and fire suppression in this region altered the ecology to favor [[oak–hickory forest]]s, instead of coniferous forests and [[grasslands]].<ref name = NRS1/><ref name = GTR234/><ref name = NRS2/> Subsequently, the host for the disease became more prevalent and promoted oak wilt infections. Moving [[timber]] during the late [[19th Century]] and early [[20th Century]], in the [[Rail_transportation_in_the_United_States#1851–1900|period of railroad expansion]], coincides with the discovery of the oak wilt disease in the United States.
The asexual stage of oak wilt was first described in 1942 in Wisconsin.<ref name = henry/><ref name = bretz/> Soon thereafter the disease was reported throughout the [[Upper Midwest forest–savanna transition|Upper Midwest]] and [[Central forest–grasslands transition|Central]] forests. The early [[History of the lumber industry in the United States#Twentieth century|20th Century]] coincided with oak regeneration after significant logging in the [[Mid-Atlantic (United States)|Mid-Atlantic]] and [[Great Lakes region]]. [[Deforestation in the United States|Deforestation]] and fire suppression in this region altered the ecology to favor [[oak–hickory forest]]s, instead of coniferous forests and [[grasslands]].<ref name = NRS1/><ref name = GTR234/><ref name = NRS2/> Subsequently, the host for the disease became more prevalent and promoted oak wilt infections. Moving timber during the late 19th Century and early 20th Century, in the [[Rail transportation in the United States#1851–1900|period of railroad expansion]], coincides with the discovery of the oak wilt disease in the United States.


The origin of the disease is unknown, but probably emerged from [[Mexico]], [[Central America]], or [[South America]].<ref name = AnnRev1/> Mexico is the global center of oak diversity, supporting it as the [[Endemism|endemic range]] of oak wilt.<ref name = NewPHY1/><ref name = TreePHY2/> Any [[Biological pest control|biocontrol]] or [[Plant disease resistance|disease resistance]] for this pathogen will likely come from Mexico. The disease currently affects much of the eastern and central US, from northern [[New York (state)|New York]] to [[Central Texas]].<ref name = NYS1 /> It is particularly common in the [[Midwestern United States|Midwest]] where conditions are usually favorable for spore production and beetle activity during spring and early summer. Oak wilt is a major problem in [[Illinois]], [[Iowa]], [[Michigan]], [[Minnesota]], [[Texas]], and [[Wisconsin]].<ref name = Minn1 /><ref name = WIDNR2/><ref name = WIDNR1/>
The origin of the disease is unknown, but probably emerged from Mexico, Central America, or South America.<ref name = AnnRev1/> Mexico is the global center of oak diversity, supporting it as the [[Endemism|endemic range]] of oak wilt.<ref name = NewPHY1/><ref name = TreePHY2/> Any [[Biological pest control|biocontrol]] or [[Plant disease resistance|disease resistance]] for this pathogen will likely come from Mexico. The disease currently affects much of the eastern and central US, from northern New York to [[Central Texas]].<ref name = NYS1 /> It is particularly common in the [[Midwestern United States|Midwest]] where conditions are usually favorable for spore production and beetle activity during spring and early summer. Oak wilt is a major problem in [[Illinois]], [[Iowa]], [[Michigan]], [[Minnesota]], [[Texas]], and [[Wisconsin]].<ref name = Minn1 /><ref name = WIDNR2/><ref name = WIDNR1/>


==Disease Cycle==
=== Disease cycle ===
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| title = Oak wilt disease cycle
| title = Oak wilt disease cycle
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[[File:OakWiltLineDrawings2.png|thumb|right|upright=1.3|Illustration of ''Bretziella fagacearum'']]
[[File:OakWiltLineDrawings2.png|thumb|right|upright=1.3|Illustration of ''Bretziella fagacearum'']]
[[File:OakWiltHerbarium2.png|thumb|right|upright=1.3|Photograph of ''Bretziella fagacearum'']]
[[File:OakWiltHerbarium2.png|thumb|right|upright=1.3|Photograph of ''Bretziella fagacearum'']]
The fungus overwinters on dead tissue from diseased trees. Symptoms first appear in spring and summer. Highly susceptible species typically die within one year (often within six weeks) after symptoms appear. Symptoms begin in the tops of trees and can be difficult to notice. The disease progresses inward and downward from the [[Canopy (biology)|tree top]]. Leaves become [[Chlorosis| chlorotic]] beginning at the [[Leaf#Apex_(tip)|leaf tip]] and [[Leaf#Edge_(margin)| leaf edges]]. An abrupt demarcation of chlorotic [[Leaf#Veins| veins]] and green tissue is often a distinguishing characteristic in live oak infections.<ref name = TXOW1 /> The foliage may droop, curl lengthwise, wilt, and begin to [[Abscission| fall]]. Leaves drop from the tree in the middle of [[summer]], however less susceptible trees may retain leaves longer and resemble seasonal [[Leaf#Seasonal_leaf_loss| autumn foliage]]. Highly susceptible species will exhibit rapid [[Crown (botany)|crown]] dieback, while less susceptible species may only lose a few scattered branches. Live oaks may survive several years with progressive dieback, but often die within six months. Following [[Defoliant| defoliation]], fungal [[Sporocarp (fungi)|fruiting bodies]] develop from [[mycelium]] under the [[Bark (botany)|bark]] of the tree. The mats grow to 10 - 20 cm in size, elliptical in shape, and grey in color with white margins that darken with age. These mats are not found on live oaks and rarely on white oaks. Trees capable of producing mats are called potential spore-producing trees (PSPT). Brown streaks in the [[Wood#Heartwood_and_sapwood| sapwood]] is also observed in the oak wilt disease. However, this symptom is not always associated with the disease.
The fungus overwinters on dead tissue from diseased trees. Symptoms first appear in spring and summer. Highly susceptible species typically die within one year (often within six weeks) after symptoms appear. Symptoms begin in the tops of trees and can be difficult to notice. The disease progresses inward and downward from the [[Canopy (biology)|tree top]]. Leaves become [[Chlorosis|chlorotic]] beginning at the [[Leaf#Apex (tip)|leaf tip]] and [[Leaf#Edge (margin)|leaf edges]]. An abrupt demarcation of chlorotic [[Leaf#Veins|veins]] and green tissue is often a distinguishing characteristic in live oak infections.<ref name = TXOW1 /> The foliage may droop, curl lengthwise, wilt, and begin to [[Abscission|fall]]. Leaves drop from the tree in the middle of summer, however less susceptible trees may retain leaves longer and resemble seasonal [[Leaf#Seasonal leaf loss|autumn foliage]]. Highly susceptible species will exhibit rapid [[Crown (botany)|crown]] dieback, while less susceptible species may only lose a few scattered branches. Live oaks may survive several years with progressive dieback, but often die within six months. Following [[Defoliant|defoliation]], fungal [[Sporocarp (fungi)|fruiting bodies]] develop from [[mycelium]] under the [[Bark (botany)|bark]] of the tree. The mats grow to 10 – 20&nbsp;cm in size, elliptical in shape, and grey in color with white margins that darken with age. These mats are not found on live oaks and rarely on white oaks. Trees capable of producing mats are called potential spore-producing trees (PSPT). Brown streaks in the [[Wood#Heartwood and sapwood|sapwood]] is also observed in the oak wilt disease. However, this symptom is not always associated with the disease.


The oak wilt fungus can spread from diseased trees to healthy trees in several ways. The disease can spread long distances (overland) by [[Airborne transmission |airborne]] spores in open [[Wound response in plants|wounds]] caused by [[Ecophysiology#Wind_damage|wind damage]], [[pruning]], or other mechanical damage. Alternatively, under ideal conditions (temperature, moisture content, wood pH) spore mats form under the bark of the dead tree. Spore mats develop in the spring or fall for 2 -3 weeks. The center of spore mats produce chains of barrel shaped spores, called endoconidia. [[Conidia]] are asexual spores dispersed by air, rain, and insects.<ref name = EU1 /> If compatible mating types are present, these mats will also produce sexual spores called ascospores in fruiting structures called [[perithecia]]. [[Ascospores]] are spread by water and insects.<ref name = EU1 /> These spore mats (or pressure pads) increase in size, eventually breaking through the bark and releasing a fruity odor that attracts wildlife, including [[Nitidulidae|sap beetles]], [[bark beetles]], other [[insects]], [[birds]] and [[animals]], such as [[squirrels]]. Insect [[Vector (epidemiology) |vectors]] transmit the disease in spring to early summer in the Mid-West and late Winter in Texas. Insect transmission is the primary way new [[Focus of infection| infection foci]] originate.
The oak wilt fungus can spread from diseased trees to healthy trees in several ways. The disease can spread long distances (overland) by [[Airborne transmission|airborne]] spores in open [[Wound response in plants|wounds]] caused by [[Ecophysiology#Wind damage|wind damage]], [[pruning]], or other mechanical damage. Alternatively, under ideal conditions (temperature, moisture content, wood pH) spore mats form under the bark of the dead tree. Spore mats develop in the spring or fall for 2–3 weeks. The center of spore mats produce chains of barrel shaped spores, called endoconidia. [[Conidia]] are asexual spores dispersed by air, rain, and insects.<ref name = EU1 /> If compatible mating types are present, these mats will also produce sexual spores called ascospores in fruiting structures called [[perithecia]]. [[Ascospores]] are spread by water and insects.<ref name = EU1 /> These spore mats (or pressure pads) increase in size, eventually breaking through the bark and releasing a fruity odor that attracts wildlife, including [[Nitidulidae|sap beetles]], [[bark beetles]], other insects, birds and animals, such as squirrels. Insect [[Vector (epidemiology)|vectors]] transmit the disease in spring to early summer in the Mid-West and late Winter in Texas. Insect transmission is the primary way new [[Focus of infection|infection foci]] originate.


The fungus can spread short distances through naturally occurring [[root]] grafts. Root [[grafting|grafts]] form when two or more underground roots merge together from adjacent trees. Typically, [[root]]s from the same, or similar species, can form root grafts as their [[Vascular cambium| cambia]] are pressed together and combine.<ref name = phys4/><ref name = SITN1/> Fungal spores in the [[xylem]] travel to nearby trees through these root grafts and can rapidly kill many trees simultaneously. This transmission method accounts for the vast majority of infections and is particularly devastating as groups of trees are killed. The disease can extend 10 - 20m per year (40m per year in Texas) from the [[Focus of infection| infection foci]] to surrounding trees. Diseased trees can continue to harbor and transmit the disease for several years through the root network.
The fungus can spread short distances through naturally occurring [[root]] grafts. Root [[grafting|grafts]] form when two or more underground roots merge from adjacent trees. Typically, [[root]]s from the same, or similar species, can form root grafts as their [[Vascular cambium|cambia]] are pressed together and combine.<ref name = phys4/><ref name = SITN1/> Fungal spores in the [[xylem]] travel to nearby trees through these root grafts and can rapidly kill many trees simultaneously. This transmission method accounts for the vast majority of infections and is particularly devastating as groups of trees are killed. The disease can extend 10 – 20m per year (40m per year in Texas) from the [[Focus of infection|infection foci]] to surrounding trees. Diseased trees can continue to harbor and transmit the disease for several years through the root network.


The disease results from fungal spores clogging [[xylem]] vessels and preventing water and nutrient flow. [[Mycelia]] growth between and through [[Vessel element| vessels]] end up blocking [[Pit (botany)|xylem pits]] in the vessel endwalls. [[Tylose]] protrusion and the accumulation of 'gums' will further obstruct vessels. Tylose is a outgrowth of [[Ground_tissue#Parenchyma| parenchyma]] cells created as a plant defense against pathogens, water deficiency, wounding, and [[Wood#Heartwood_and_sapwood| heartwood]] formation. Tylose formation signals senescence of adjacent parenchyma cells and secretion of [[secondary metabolites]] (called gums), which may include phenolics.<ref name = path3/> The interruption of the xylem vessels precedes tylose formation. Tylose and secreted gums act as a barrier to slow the colonization of the pathogen and play an important part in [[Plant use of endophytic fungi in defense|plant defenses]]. However, the action to [[Compartmentalization of decay in trees| compartmentalize]] the oak wilt fungus ultimately obstructs all water conductance, leading to death. The fungus can survive in the xylem for multiple years, if the tree is not killed.
The disease results from fungal spores clogging [[xylem]] vessels and preventing water and nutrient flow. [[Mycelia]] growth between and through [[Vessel element|vessels]] end up blocking [[Pit (botany)|xylem pits]] in the vessel endwalls. [[Tylose]] protrusion and the accumulation of 'gums' will further obstruct vessels. Tylose is an outgrowth of [[Ground tissue#Parenchyma|parenchyma]] cells created as a plant defense against pathogens, water deficiency, wounding, and [[Wood#Heartwood and sapwood|heartwood]] formation. Tylose formation signals senescence of adjacent parenchyma cells and secretion of [[secondary metabolites]] (called gums), which may include phenolics.<ref name = path3/> The interruption of the xylem vessels precedes tylose formation. Tylose and secreted gums act as a barrier to slow the colonization of the pathogen and play an important part in [[Plant use of endophytic fungi in defense|plant defenses]]. However, the action to [[Compartmentalization of decay in trees|compartmentalize]] the oak wilt fungus ultimately obstructs all water conductance, leading to death. The fungus can survive in the xylem for multiple years, if the tree is not killed.
{{Quote box
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|title= Oak Wilt Management Quick Guide
|title= Oak Wilt Management Quick Guide
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* '''Inject High-Value Oaks with Fungicide'''
* '''Inject High-Value Oaks with Fungicide'''
** Identify susceptible, high-value oak trees in proximity to expanding oak wilt infection centers.
** Identify susceptible, high-value oak trees in proximity to expanding oak wilt infection centers.
** Consult a trained and licensed arborist (with certified applicator’s license) for treatment of susceptible trees with injections of propiconazole.
** Consult a trained and licensed arborist (with certified applicator's license) for treatment of susceptible trees with injections of propiconazole.
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=Management=
== Management ==
{{multiple image|perrow = 2|total_width=400
{{multiple image|perrow = 2|total_width=400
| image1 = The Real Dr Spore Mat.jpg
| image1 = The Real Dr Spore Mat.jpg
| image2 = Spore_Mats_Stage_IV-V.jpg
| image2 = Spore_Mats_Stage_IV-V.jpg
| caption1 = Wood caramel colored, spore mats stage III is infectious
| caption1 = Wood caramel colored, spore mats stage III is infectious
| caption2 = Spore mats (dark patches) stage IV - V are no longer infectious
| caption2 = Spore mats (dark patches) stage IV – V are no longer infectious
| alt1 = Photograph of person pointing to spore mat
| alt1 = Photograph of person pointing to spore mat
| alt2 = Photograph of dead tree trunk
| alt2 = Photograph of dead tree trunk
| footer =
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Elimination of the disease is not possible; therefore, managing the disease is essential to prevent economic and ecological losses.<ref name = path1/> Management of the oak wilt disease includes [[forest integrated pest management]]; such as sanitation, chemical application, and cultural control. Ideally, several methods are used in conjunction to enhance disease control. Any chosen method relies on specific landowner objectives; such as protecting high value trees, treating individual trees, halting or slowing the spread of an infection center, and reducing the number of new infection foci. All methods depend on timely [[Crop scouting|detection]] and accurate diagnosis of the disease to be beneficial. [[Aerial photography| Aerial observation]] (or [[remote sensing]]) is able to identify infected forest stands by observing the dead [[Crown (botany) |crowns]] of trees in summer. The use of [[spectroscopy]] is being developed for large scale detection and monitoring of oak wilt.<ref name = TreePHY1 />
Elimination of the disease is not possible; therefore, managing the disease is essential to prevent economic and ecological losses.{{citation needed|date=December 2020}} Management of the oak wilt disease includes [[forest integrated pest management]]; such as sanitation, chemical application, and cultural control. Ideally, several methods are used in conjunction to enhance disease control. Any chosen method relies on specific landowner objectives; such as protecting high value trees, treating individual trees, halting or slowing the spread of an infection center, and reducing the number of new infection foci. All methods depend on timely [[Crop scouting|detection]] and accurate diagnosis of the disease to be beneficial. [[Aerial photography|Aerial observation]] (or [[remote sensing]]) is able to identify infected forest stands by observing the dead [[Crown (botany)|crowns]] of trees in summer. The use of [[spectroscopy]] is being developed for large scale detection and monitoring of oak wilt.<ref name = TreePHY1 />


==Chemical Control==
=== Chemical control ===
Chemical control can be preventative or [[therapeutic]], depending on risk and resources available. [[Propiconazole]] is the principle [[fungicide]] for treatment against oak wilt. Propiconazole is a [[Broad-spectrum antibiotic|broad-spectrum]] [[Pesticide|systemic fungicide]] that interferes with the [[biosynthesis]] of [[ergosterol]] in [[cell membranes]] by binding to [[Lanosterol 14 alpha-demethylase|14 alpha-demethylase]]. [[Tree injection]] is the preferred application method to deliver targeted control. Tree injections involve intravascular injections with [[positive pressure]] to force the chemical throughout the vascular system of the tree. This method is relatively expensive and requires a trained [[arborist]] to perform .<ref name = YT2/><ref name = YT3/> Propiconazole injection does not offer protection to neighboring trees and must be applied to all target trees.
Chemical control can be preventative or therapeutic, depending on risk and resources available. [[Propiconazole]] is the principle [[fungicide]] for treatment against oak wilt. Propiconazole is a [[Broad-spectrum antibiotic|broad-spectrum]] [[Pesticide|systemic fungicide]] that interferes with the [[biosynthesis]] of [[ergosterol]] in [[cell membranes]] by binding to [[Lanosterol 14 alpha-demethylase|14 alpha-demethylase]]. [[Tree injection]] is the preferred application method to deliver targeted control. Tree injections involve intravascular injections with [[positive pressure]] to force the chemical throughout the vascular system of the tree. This method is relatively expensive and requires a trained [[arborist]] to perform .<ref name = YT2/><ref name = YT3/> Propiconazole injection does not offer protection to neighboring trees and must be applied to all target trees.


Preventative propiconazole application does not prevent infection, rather it delays symptoms and reduces mortality. All oak species studied have benefited from preventative propiconazole treatment.<ref name = urban2/> This method is often applied to high value trees in an urban area, specifically Northern red oaks and live oaks. White oaks are more disease resistant, thus preventative treatment is unnecessary. Likewise, therapeutic propiconazole application does not eradicate the fungal infection, rather it delays symptoms and reduces mortality. Highly susceptible red oaks rarely benefit from therapeutic treatment, but symptomatic white oaks improve with treatment. Asymptomatic live oaks will respond better to propiconazole treatment than symptomatic trees.
Preventative propiconazole application does not prevent infection, rather it delays symptoms and reduces mortality. All oak species studied have benefited from preventative propiconazole treatment.<ref name = urban2/> This method is often applied to high value trees in an urban area, specifically Northern red oaks and live oaks. White oaks are more disease resistant, thus preventative treatment is unnecessary. Likewise, therapeutic propiconazole application does not eradicate the fungal infection, rather it delays symptoms and reduces mortality. Highly susceptible red oaks rarely benefit from therapeutic treatment, but symptomatic white oaks improve with treatment. Asymptomatic live oaks will respond better to propiconazole treatment than symptomatic trees.


[[spring (season)|Spring]] application is the most effective time for chemical treatment. Multiple applications, every two years, may be necessary for long-term disease control.
Spring application is the most effective time for chemical treatment. Multiple applications, every two years, may be necessary for long-term disease control.

==Cultural Control==
===Mechanical===
=== Cultural Control ===
==== Mechanical ====
Mechanical separation of the underground root connections will not allow the disease to transfer to adjacent trees. However, ensuring all root connections are severed is difficult and impractical to verify. Notwithstanding, digging a trench (or plowline) four feet deep around infected trees is an effective cultural control strategy. The plowline should encompass any infected tree. In practice this consists of all trees expected to be connected by a root graft with an infected tree, in addition to all symptomatic trees. In the Mid-West, a plowline 50 feet away from infected trees is recommended. In [[Central Texas]], [[live oak]] [[lateral roots]] grow at a shallow depth in rocky soil, allowing an extensive root network with neighboring trees. For this reason, a plowline 100 feet away from infected trees is recommended.<ref name = path2/> A second plowline between all symptomatic trees and visibly healthy trees will reinforce this control strategy.
Mechanical separation of the underground root connections will not allow the disease to transfer to adjacent trees. However, ensuring all root connections are severed is difficult and impractical to verify. Notwithstanding, digging a trench (or plowline) four feet deep around infected trees is an effective cultural control strategy. The plowline should encompass any infected tree. In practice this consists of all trees expected to be connected by a root graft with an infected tree, in addition to all symptomatic trees. In the Mid-West, a plowline 50 feet away from infected trees is recommended. In [[Central Texas]], [[live oak]] [[lateral roots]] grow at a shallow depth in rocky soil, allowing an extensive root network with neighboring trees. For this reason, a plowline 100 feet away from infected trees is recommended.<ref name = path2/> A second plowline between all symptomatic trees and visibly healthy trees will reinforce this control strategy.


The plowline can be created with [[agricultural machinery]], such as an [[excavator]], rock saw, vibratory plow, and bulldozer with [[Bulldozer#Ripper|ripper]] or [[subsoiler]]. Equipment costs and availability will vary.
The plowline can be created with [[agricultural machinery]], such as an [[excavator]], rock saw, vibratory plow, and bulldozer with [[Bulldozer#Ripper|ripper]] or [[subsoiler]]. Equipment costs and availability will vary.


The placement of a root barrier can offer additional protection to trenching, but increases [[total costs]]. A [[geomembrane]] is a [[Semipermeable membrane|semipermeable]] [[textile]] (similar to [[landscape fabric]]) that physically blocks roots from coming into contact. It is essential that trenching and geomembrane installation occur before removing infected trees.
The placement of a root barrier can offer additional protection to trenching, but increases [[total costs]]. A [[geomembrane]] is a [[Semipermeable membrane|semipermeable]] textile (similar to [[landscape fabric]]) that physically blocks roots from coming into contact. It is essential that trenching and geomembrane installation occur before removing infected trees.


===Sanitation===
==== Sanitation ====
[[File:Kost_Oak_Savanna_OW_cleanup_autumn_2007.jpg|thumb|right|alt=Oak wilt and buckthorn cleanup on oak savanna in Chisago County, Minnesota autumn/after leaf drop 2007| Cultural control (sanitation) of oak wilt infection area]]
[[File:Kost_Oak_Savanna_OW_cleanup_autumn_2007.jpg|thumb|right|alt=Oak wilt and buckthorn cleanup on oak savanna in Chisago County, Minnesota autumn/after leaf drop 2007| Cultural control (sanitation) of oak wilt infection area]]
Sanitation entails removing [[Infection| infectious material]] to reduce [[Inoculation| inoculum]] before new infections a can develop. Red oaks are the only group capable of forming spore mats, designated as PSPTs. Therefore, removing any PSPTs that become infected is esential to minimize new infection foci. Furthermore, removing all PSPTs, regardless of symptoms, within an infected area reinforces the process. In practice this consists of removing all PSPTs within the plowline (see [[Oak_wilt#Mechanical| Mechanical]]). Trees will need to be removed annually to sustain control over the years. Tree removal involves [[felling]] and burying or burning the [[Logging| logs]], ensuring all inoculum is discarded. Alternatively, logs and [[Slash (logging)|slash]] can be [[Woodchips| chipped]] or [[Mulch| mulched]] on site. Tree stumps can also be removed to increase sanitation.
Sanitation entails removing [[Infection|infectious material]] to reduce [[Inoculation|inoculum]] before new infections can develop. Red oaks are the only group capable of forming spore mats, designated as PSPTs. Therefore, removing any PSPTs that become infected is essential to minimize new infection foci. Furthermore, removing all PSPTs, regardless of symptoms, within an infected area reinforces the process. In practice this consists of removing all PSPTs within the plowline (see [[Oak wilt#Mechanical|Mechanical]]). Trees will need to be removed annually to sustain control over the years. Tree removal involves [[felling]] and burying or burning the [[Logging|logs]], ensuring all inoculum is discarded. Alternatively, logs and [[Slash (logging)|slash]] can be [[Woodchips|chipped]] or [[mulch]]ed on site. Tree stumps can also be removed to increase sanitation.


[[Girdling]] infected trees is another method to reduce the spread of oak wilt; although, not as effective as whole tree removal. Girdling requires the complete detachment of the [[cambium]] from the PSPTs. Moreover, [[Debarking (lumber)|debarking]] the trunk of the tree (up to 4 feet) is essential. Oak wilt does not produce fruiting bodies on dead or dry wood. Debarking speeds the drying process and assists [[Hypoxylon|Hypoxylon coccineum]] in colonizing the wood.
[[Girdling]] infected trees is another method to reduce the spread of oak wilt; although, not as effective as whole tree removal. Girdling requires the complete detachment of the [[cambium]] from the PSPTs. Moreover, [[Debarking (lumber)|debarking]] the trunk of the tree (up to 4 feet) is essential. Oak wilt does not produce fruiting bodies on dead or dry wood. Debarking speeds the drying process and assists [[Hypoxylon]] coccineum in colonizing the wood.


[[Nitidulidae|Sap beetles]] are opportunistic insects, incapable of penetrating a tree without an open wound. Therefore, avoid [[pruning]] or felling oak trees when fungal spores and beetles are active. In the Mid-West avoid injuring oaks from April to October and prune limbs after the first hard frost, or from November until April. In Texas avoid pruning oaks from February through June. Moreover, clean pruning equipment between each tree and apply [[tree paint]] to any injury or open [[Wound response in plants| wound]]. Injuries often occur during [[construction]] and [[severe weather]].
[[Nitidulidae|Sap beetles]] are opportunistic insects, incapable of penetrating a tree without an open wound. Therefore, avoid [[pruning]] or felling oak trees when fungal spores and beetles are active. In the Mid-West avoid injuring oaks from April to October and prune limbs after the first hard frost, or from November until April. In Texas avoid pruning oaks from February through June. Moreover, clean pruning equipment between each tree and apply [[tree paint]] to any injury or open [[Wound response in plants|wound]]. Injuries often occur during construction and [[severe weather]].


===Silviculture===
==== Silviculture ====
[[Silviculture]] involves keeping a forest healthy. Typically, a healthy forest with healthy trees will be more resistant to pests and diseases. [[Thinning]] is the process of removing unwanted trees to promote the growth of the desired trees. Oaks are shade intolerant species. Releasing (or thinning) oaks from competition provides more light, moisture, and nutrients to the remaining oaks. Overall the oaks become stronger, more healthy, and more capable to resist pests and disease.
[[Silviculture]] involves keeping a forest healthy. Typically, a healthy forest with healthy trees will be more resistant to pests and diseases. [[Thinning]] is the process of removing unwanted trees to promote the growth of the desired trees. Oaks are shade intolerant species. Releasing (or thinning) oaks from competition provides more light, moisture, and nutrients to the remaining oaks. Overall the oaks become stronger, more healthy, and more capable to resist pests and disease.


Increasing tree [[Measurement of biodiversity|species diversity]] (i.e. [[species evenness]]) in a forest is another method to lessen the impact of the disease. Evidence shows increasing [[Diversity index|diversity]] in a landscape can increase forest resilance to pests and disease.<ref name = Plant1/><ref name = EE1/><ref name = EL1/><ref name = ForEnto1/> Moreover, increasing diversity can increase soil microbial communities and ecosystem services.<ref name = NatCom1/><ref name = ComBio1/><ref name = Oikos1/><ref name = PRSB1/><ref name = PNAS1/>
Increasing tree [[Measurement of biodiversity|species diversity]] (i.e. [[species evenness]]) in a forest is another method to lessen the impact of the disease. Evidence shows increasing [[Diversity index|diversity]] in a landscape can increase forest resilience to pests and disease.<ref name = Plant1/><ref name = EE1/><ref name = EL1/><ref name = ForEnto1/> Moreover, increasing diversity can increase soil microbial communities and [[ecosystem service]]s.<ref name = NatCom1/><ref name = ComBio1/><ref name = Oikos1/><ref name = PRSB1/><ref name = PNAS1/>


==Education==
=== Education ===
[[Education]] is the most valuable tool to combat the spread of pests and diseases. In this context, warning the [[public]] about the spread of oak wilt by humans. Specifically, people take [[fuelwood]] from one location to another location, often long distances. This action is responsible for moving pathogens in those [[Logging| logs]] to places they are not currently present. Spreading oak wilt to new locations through firewood is a major problem. Moreover, covering [[firewood]] with clear plastic can [[Soil solarization| solarize]] the wood pile and eradicate any pathogens.
Education is the most valuable tool to combat the spread of pests and diseases. In this context, warning the [[public]] about the spread of oak wilt by humans. Specifically, people take [[fuelwood]] from one location to another location, often long distances. This action is responsible for moving pathogens in those [[Logging|logs]] to places they are not currently present. Spreading oak wilt to new locations through firewood is a major problem. Moreover, covering [[firewood]] with clear plastic can [[Soil solarization|solarize]] the wood pile and eradicate any pathogens.
{{Quote box
{{Quote box
|quote = '''Prevent the spread of invasive species and diseases'''
|quote = '''Prevent the spread of invasive species and diseases'''
* Don’t take firewood with you on your camping trip, RV adventure, or to your hunting camp.
* Don't take firewood with you on your camping trip, RV adventure, or to your hunting camp.
* Don’t bring firewood back from your second home to your place in the suburbs.
* Don't bring firewood back from your second home to your place in the suburbs.
* Buy firewood near where you will burn it, or gather firewood on site when permitted.
* Buy firewood near where you will burn it, or gather firewood on site when permitted.
** A good rule of thumb is only using wood that was cut within 50 miles of where you’ll have your fire.
** A good rule of thumb is only using wood that was cut within 50 miles of where you'll have your fire.
* Certified heat-treated firewood is safe to move long distances.
* Certified heat-treated firewood is safe to move long distances.
* Aged or seasoned wood is still not safe.
* Aged or seasoned wood is still not safe.
** Just because it is dry doesn’t mean that bugs can’t crawl onto it- and some insects can take several years to mature inside the wood.
** Just because it is dry doesn't mean that bugs can't crawl onto it- and some insects can take several years to mature inside the wood.
** Wood that looks clean and healthy can still have tiny insect eggs, or microscopic fungi spores, that will start a new and deadly infestation.
** Wood that looks clean and healthy can still have tiny insect eggs, or microscopic fungi spores, that will start a new and deadly infestation.
|align = center
|align = center
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{{Gallery
{{Gallery
| File: Kerrick_Oak_Wilt_8-19-16_Spawned-_from_7-1-2011_Infection_Centers.png
| File: Kerrick_Oak_Wilt_8-19-16_Spawned-_from_7-1-2011_Infection_Centers.png
| alt1 = North Flank of 7-1-2011 Windstorm went thru northern Pine and Carlton Counties Minnesota. Photo shows hilltop infections from May 24–25, 2016 wind & hailstorms; spores came from 7-1-11 storm-created infection center near Kerrick, Minnesota
| alt1 = North Flank of 7 January 2011 Windstorm went thru northern Pine and Carlton Counties Minnesota. Photo shows hilltop infections from 24–25 May 2016 wind & hailstorms; spores came from 7-1-11 storm-created infection center near Kerrick, Minnesota
| Infected trees
| Infected trees
| File: East_Farmington_3_Infection_Centers_photo_taken_8-8-16.png
| File: East_Farmington_3_Infection_Centers_photo_taken_8-8-16.png
| alt2 = South Flank of 7-1-2011 Windstorm went thru St. Croix County, Wisconsin. Photo shows one of five 7-1-11 infection centers on hilltop near East Farmington, Wisconsin
| alt2 = South Flank of 7 January 2011 Windstorm went thru St. Croix County, Wisconsin. Photo shows one of five 7-1-11 infection centers on hilltop near East Farmington, Wisconsin
| Infection foci on hilltop
| Infection foci on hilltop
| File: White_Oak_on_Nymore_soils_Chisago_County_2012.jpg
| File: White_Oak_on_Nymore_soils_Chisago_County_2012.jpg
Line 188: Line 182:
| White oak after storm damage
| White oak after storm damage
| File:West of Grasston Oak Wilt Pic 8-20-12 SE Sec10 T38-R23.jpg
| File:West of Grasston Oak Wilt Pic 8-20-12 SE Sec10 T38-R23.jpg
| alt4 = Northern Pin Oak overland Infection on field edge from July 1, 2011 Windstorm, West of Grasston, Kanabec County, Minnesota
| alt4 = Northern Pin Oak overland Infection on field edge from 1 July 2011 Windstorm, West of Grasston, Kanabec County, Minnesota
| Northern pin oak overland infection
| Northern pin oak overland infection
| footer = Photos from [[c: File:24 - 25 May 2016 NOAA NWS Storm Maps.pdf | May 24–25, 2016 wind & hailstorms]]<ref name = NWS1 />
| footer = Photos from [[c: File:24 - 25 May 2016 NOAA NWS Storm Maps.pdf|Far left – 24–25 May 2016 wind & hailstorms, next three 1 July 2011 windstorm]]<ref name = NWS1 />
}}
}}
==See also==
⚫
* [[Japanese oak wilt]] - caused by ''Raffaelea quercivora'' in Japan
⚫
* [[Sudden oak death]] - caused by ''Phytophthora ramorum''


==References==
=== See also ===
⚫
* [[Japanese oak wilt]] – caused by ''Raffaelea quercivora'' in Japan
⚫
* [[Sudden oak death]] – caused by ''Phytophthora ramorum''

=== References ===
{{Reflist|refs=
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<ref name = urban2>{{cite journal |last1=Koch |first1=Karrie A. |last2= Quiram |first2=Gina L. |last3= Venette |first3=Robert C. |date=2010 |title=A review of oak wilt management: A summary of treatment options and their efficacy |url=https://www.nrs.fs.fed.us/pubs/jrnl/2010/nrs_2010_koch-k_001.pdf |journal= Urban Forestry & Urban Greening |publisher= Elsevier GmbH |volume= 9 |issue= |pages= |doi=10.1016/j.ufug.2009.11.004 |access-date=2020-11-05}}</ref>
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<ref name = path1>{{cite journal |last1=Wilson |first1=Dan A.|date=2005| title=Recent advances in the control of oak wilt in the United States |url=https://www.fs.usda.gov/treesearch/pubs/21644 |journal= Plant Pathology |publisher= Oxford University Press |volume= 7 |issue=2 |pages=177-191 |doi= |access-date=2020-11-05}}</ref>
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<ref name = UK1>{{cite web |url=https://www.forestresearch.gov.uk/tools-and-resources/pest-and-disease-resources/oak-wilt-ceratocystis-fagacearum/ |title=Oak wilt (Ceratocystis fagacearum) |website=forestresearch.gov.uk |publisher= Forest Commission (UK)|access-date=19 October 2020 }}</ref>
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<ref name = path3>{{cite journal |last1=Rioux |first1=D.|last2=Nicole |first2=M.|last3=Simard |first3=M.|last4=Ouellette |first4=G.B.|date=1998| title=Immunocytochemical Evidence that Secretion of Pectin Occurs During Gel (Gum) and Tylosis Formation in Trees |journal= Phytopathology |publisher= The American Phytopathological Society |volume= 88 |issue= 6 |pages=494–505|doi=10.1094/PHYTO.1998.88.6.494|pmid=18944900|doi-access= }}</ref>
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<ref name = UK1>{{cite web |url=https://www.forestresearch.gov.uk/tools-and-resources/pest-and-disease-resources/oak-wilt-ceratocystis-fagacearum/ |title=Oak wilt (Ceratocystis fagacearum) |last= |first= |date= |website=forestresearch.gov.uk |publisher= Forest Commission (UK)|access-date=2020-10-19 |quote=}}</ref>
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<ref name = NewPHY1>{{cite journal |vauthors= Fallon B, Yang A, Lapadat C, Armour I, Juzwik J, Montgomery RA, and Cavender-Bares J |date=2018 |title=Sympatric parallel diversification of major oak clades in the Americas and the origins of Mexican species diversity |journal=New Phytologist |volume=217 |issue=1 |pages=439–452 |publisher= John Wiley & Sons, Inc.|doi=10.1111/nph.14773 |pmid=28921530 |doi-access=free }}</ref>
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<ref name = path3>{{cite journal |last1=Rioux |first1=D.|last2=Nicole |first2=M.|last3=Simard |first3=M.|last4=Ouellette |first4=G.B.|date=1998| title=Immunocytochemical Evidence that Secretion of Pectin Occurs During Gel (Gum) and Tylosis Formation in Trees |url=https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO.1998.88.6.494 |journal= Phytopathology |publisher= The American Phytopathological Society |volume= 88 |issue= 6 |pages= |doi= |access-date=2020-11-05}}</ref>
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<ref name = NRS1>{{cite web |url=https://www.nrs.fs.fed.us/fmg/nfmg/fm101/eco/p1_historical.html#:~:text=Prior%20to%20Euro%2DAmerican%20settlement,forests%20and%20oak%20savannas%2C%20mesic |title=Historical ecology of the upper midwest |date=2006 |website=nrs.fs.fed.us |publisher= USFS Northern Research Station |access-date=19 October 2020 |archive-date=2017-07-02|archive-url=https://web.archive.org/web/20170702210336/https://www.nrs.fs.fed.us/fmg/nfmg/fm101/eco/p1_historical.html}}</ref>
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<ref name = NewPHY1>{{cite journal |vauthors= Fallon B, Yang A, Lapadat C, Armour I, Juzwik J, Montgomery RA, and Cavender-Bares J |date=2018 |title=Sympatric parallel diversification of major oak clades in the Americas and the origins of Mexican species diversity |url=https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.14773 |journal=New Phytologist |volume=217 |issue= |pages=439-452 |publisher= John Wiley & Sons, Inc.|doi=10.1111/nph.14773 |pmc= |pmid= |access-date=}}</ref>
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<ref name = GTR234>{{cite journal |vauthors= Van Sambeek JW, Dawson JO, Ponder F Jr, Loewenstein EF, Fralish JS |date=2003 |title=The Central Hardwood Forest: Its Boundaries and Physiographic Provinces |url=https://www.fs.usda.gov/treesearch/pubs/12317 |journal=Proceedings of the 13th Central Hardwood Forest Conference |volume=234 |publisher= U.S. Department of Agriculture, Forest Service, North Central Research Station }}</ref>
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<ref name = NRS1>{{cite web |url=https://www.nrs.fs.fed.us/fmg/nfmg/fm101/eco/p1_historical.html#:~:text=Prior%20to%20Euro%2DAmerican%20settlement,forests%20and%20oak%20savannas%2C%20mesic |title=Historical ecology of the upper midwest |last= |first= |date=2006 |website=nrs.fs.fed.us |publisher= USFS Northern Research Station |access-date=2020-10-19 |quote=|archive-date=2017|archive-url=https://web.archive.org/web/20170702210336/https://www.nrs.fs.fed.us/fmg/nfmg/fm101/eco/p1_historical.html}}</ref>
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<ref name = NRS2>{{cite web |url=https://www.nrs.fs.fed.us/pubs/217 |title=Perspectives on the ecology and silviculture of oak-dominated forests in the Central and Eastern States |last=Johnson |first=Paul S. |date=1992 |website=nrs.fs.fed.us |publisher= USFS Northern Research Station |access-date=19 October 2020 }}</ref>
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<ref name = GTR234>{{cite journal |vauthors= Van Sambeek JW, Dawson JO, Ponder F Jr, Loewenstein EF, Fralish JS |date=2003 |title=The Central Hardwood Forest: Its Boundaries and Physiographic Provinces |url=https://www.fs.usda.gov/treesearch/pubs/12317 |journal=Proceedings of the 13th Central Hardwood Forest Conference |volume= |issue= |pages= |publisher= U.S. Department of Agriculture, Forest Service, North Central Research Station |doi= |pmc= |pmid= |access-date=}}</ref>
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<ref name = YT1>{{cite AV media |people=David Appel |date=8 July 2008 |title=Oak Wilt Identification and Management |medium=YouTube |language=en |url=https://www.youtube.com/watch?v=WYcFosGVbaM |archive-url=https://ghostarchive.org/varchive/youtube/20211213/WYcFosGVbaM| archive-date=2021-12-13 |url-status=live|access-date=15 November 2020 }}{{cbignore}}</ref>
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<ref name = NRS2>{{cite web |url=https://www.nrs.fs.fed.us/pubs/217 |title=Perspectives on the ecology and silviculture of oak-dominated forests in the Central and Eastern States |last=Johnson |first=Paul S. |date=1992 |website=nrs.fs.fed.us |publisher= USFS Northern Research Station |access-date=2020-10-19 |quote=|archive-date=|archive-url=}}</ref>
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<ref name = SITN1>{{cite web |url=http://sitn.hms.harvard.edu/flash/2019/exploring-the-underground-network-of-trees-the-nervous-system-of-the-forest/ |title=Exploring The Underground Network of Trees – The Nervous System of the Forest |last=Lagomarsino |first=Valentina |date=6 May 2019 |website=sitn.hms.harvard.edu |publisher= Harvard University |access-date=19 October 2020 }}</ref>
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<ref name = YT1>{{cite AV media |people=David Appel |date=2008-07-08 |title=Oak Wilt Identification and Management |trans-title= |medium=YouTube |language=English |url=https://www.youtube.com/watch?v=WYcFosGVbaM |access-date=2020-11-15 |archive-url= |archive-date= |format= |time= |location= |publisher=|id= |isbn= |oclc= |quote= |ref=}}</ref>
<ref name = YT2>{{cite AV media |people=Shawn Bernick |date=10 April 2015 |title=Webinar: Management of Oak Wilt in Urban Areas |medium=YouTube |language=en |url=https://www.youtube.com/watch?v=ni7AwYjtbRY&list=WL&index=139 |archive-url=https://ghostarchive.org/varchive/youtube/20211213/ni7AwYjtbRY| archive-date=2021-12-13 |url-status=live|access-date=15 November 2020 |publisher=Rainbow Tree Service}}{{cbignore}}</ref>
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<ref name = SITN1>{{cite web |url=http://sitn.hms.harvard.edu/flash/2019/exploring-the-underground-network-of-trees-the-nervous-system-of-the-forest/ |title=Exploring The Underground Network of Trees – The Nervous System of the Forest |last=Lagomarsino |first=Valentina |date=2019-05-06 |website=sitn.hms.harvard.edu |publisher= Harvard University |access-date=2020-10-19 |quote=|archive-date=|archive-url=}}</ref>
<ref name = YT2>{{cite AV media |people=Shawn Bernick |date=2015-04-10 |title=Webinar: Management of Oak Wilt in Urban Areas |trans-title= |medium=YouTube |language=English |url=https://www.youtube.com/watch?v=ni7AwYjtbRY&list=WL&index=139 |access-date=2020-11-15 |archive-url= |archive-date= |format= |time= |location= |publisher=Rainbow Tree Service|id= |isbn= |oclc= |quote= |ref=}}</ref>
<ref name = YT3>{{cite AV media |people=Emmett Muennink and Joe Aiken |date=6 April 2020 |title=Oak Wilt: History and Management-Arborjet Webinar |medium=YouTube |language=en |url=https://www.youtube.com/watch?v=cV-C-XMc2C8&list=WL&index=141 |archive-url=https://ghostarchive.org/varchive/youtube/20211213/cV-C-XMc2C8| archive-date=2021-12-13 |url-status=live|access-date=15 November 2020 }}{{cbignore}}</ref>
<ref name = YT3>{{cite AV media |people=Emmett Muennink and Joe Aiken |date=2020-04-06 |title=Oak Wilt: History and Management-Arborjet Webinar |trans-title= |medium=YouTube |language=English |url=https://www.youtube.com/watch?v=cV-C-XMc2C8&list=WL&index=141 |access-date=2020-11-15 |archive-url= |archive-date= |format= |time= |location= |publisher=|id= |isbn= |oclc= |quote= |ref=}}</ref>
<ref name = IOS1>{{cite journal |last1=Juzwik |first1= Jennifer |date=2000 |title=An oak wilt primer |url=https://www.fs.usda.gov/treesearch/pubs/12567 |journal=International Oaks |volume=11 |pages=14–20 |publisher= The Journal of the International Oak Society }}</ref>
<ref name = IOS1>{{cite journal |last1=Juzwik |first1= Jennifer |date=2000 |title=An oak wilt primer |url=https://www.fs.usda.gov/treesearch/pubs/12567 |journal=International Oaks |volume=11 |issue= |pages=14-20 |publisher= The Journal of the International Oak Society |doi= |pmc= |pmid= |access-date=}}</ref>
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<ref name = PNAS1>{{cite journal |vauthors= Grossiord C, et. al. |date=2014 |title=Tree diversity does not always improve resistance of forest ecosystems to drought |journal=Proceedings of the National Academy of Sciences |volume=111 |issue=41 |pages=14812–14815 |publisher= The National Academy of Sciences |doi=10.1073/pnas.1411970111 |pmid=25267642 |pmc=4205672 |bibcode=2014PNAS..11114812G |doi-access=free }}</ref>
<ref name="Species Fungorum">According to [[Species Fungorum]], the current name is ''Ceratocystis fagacearum'': {{cite web |url=http://www.speciesfungorum.org/Names/GSDSpecies.asp?RecordID=294206 |title=the ''Ceratocystis fagacearum'' page |work=Species Fungorum |publisher=Royal Botanic Gardens Kew |accessdate=16 May 2021 }}</ref>
<ref name = PNAS1>{{cite journal |vauthors= Grossiord C, et. al. |date=2014 |title=Tree diversity does not always improve resistance of forest ecosystems to drought |url=https://www.pnas.org/content/111/41/14812 |journal=Proceedings of the National Academy of Sciences |volume=41 |issue=|pages=14812-14815 |publisher= The National Academy of Sciences |doi=10.1073/pnas.1411970111 |pmc= |pmid= |access-date=}}</ref>



}}
}}


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=== External links ===

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==External links==
* [https://www.fs.usda.gov/naspf/publications/how-identify-prevent-and-control-oak-wilt How to Identify, Prevent and Control Oak Wilt]
* [https://www.fs.usda.gov/naspf/publications/how-identify-prevent-and-control-oak-wilt How to Identify, Prevent and Control Oak Wilt]
* [https://web.archive.org/web/20110522191708/http://www.extension.umn.edu/distribution/naturalresources/DD3174.html Oak Wilt in Minnesota]
* [https://web.archive.org/web/20110522191708/http://www.extension.umn.edu/distribution/naturalresources/DD3174.html Oak Wilt in Minnesota]
* [https://texasoakwilt.org/ Texas Oak Wilt]
* [https://texasoakwilt.org/ Texas Oak Wilt]
* [https://oakwilt.org/ Oak Wilt - Identify Common Oak Wilt Symptoms]
* [https://tfsweb.tamu.edu/oakwiltfaqs/ Texas A&M Forest Service FAQ]
* [https://tfsweb.tamu.edu/oakwiltfaqs/ Texas A&M Forest Service FAQ]
* [https://forestinvasives.ca/Meet-the-Species/Pathogens/Oak-Wilt#70334-distribution Canadian Forest Invasives - Oak Wilt]
* [https://forestinvasives.ca/Meet-the-Species/Pathogens/Oak-Wilt#70334-distribution Canadian Forest Invasives – Oak Wilt]
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* [https://www.fs.usda.gov/naspf/sites/default/files/final-oakwiilt_us_2017.pdf Counties with Oak Wilt (2017)]
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* [https://www.fs.usda.gov/naspf/publications/how-collect-field-samples-and-identify-oak-wilt-fungus-laboratory HOW to Collect Field Samples and Identify the Oak Wilt Fungus in the Laboratory]
* [https://www.fs.usda.gov/naspf/publications/how-collect-field-samples-and-identify-oak-wilt-fungus-laboratory HOW to Collect Field Samples and Identify the Oak Wilt Fungus in the Laboratory]
* [https://www.fs.usda.gov/naspf/success-stories/forest-health-success-story-sharing-oak-wilt-advice-across-states-provinces A Forest Health Success Story Sharing Oak Wilt Advice across States, Provinces]
* [https://www.fs.usda.gov/naspf/success-stories/forest-health-success-story-sharing-oak-wilt-advice-across-states-provinces A Forest Health Success Story Sharing Oak Wilt Advice across States, Provinces]
* [https://www.fs.usda.gov/naspf/resources/oak-wilt-management-what-are-options Oak Wilt Management - What are the Options?]
* [https://www.fs.usda.gov/naspf/resources/oak-wilt-management-what-are-options Oak Wilt Management – What are the Options?]
* [https://www.fs.usda.gov/naspf/success-stories/2017/eradication-outlying-oak-wilt-infection-new-york-state Eradication of an Outlying Oak Wilt Infection in New York State]
* [https://www.fs.usda.gov/naspf/success-stories/2017/eradication-outlying-oak-wilt-infection-new-york-state Eradication of an Outlying Oak Wilt Infection in New York State]
* [https://www.fs.usda.gov/naspf/featured-projects/2017/oak-wilt-disease-threatens-oaks-eastern-united-states Oak Wilt: Disease threatens oaks in the Eastern United States]
* [https://www.fs.usda.gov/naspf/featured-projects/2017/oak-wilt-disease-threatens-oaks-eastern-united-states Oak Wilt: Disease threatens oaks in the Eastern United States]
* [https://www.fs.usda.gov/naspf/success-stories/2017/help-halting-oak-wilt Help for Halting Oak Wilt]
* [https://www.fs.usda.gov/naspf/success-stories/2017/help-halting-oak-wilt Help for Halting Oak Wilt]
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Latest revision as of 08:24, 1 December 2024

Oak wilt
Aerial photograph of an oak wilt center (St. Paul, MN)
Causal agentsBretziella fagacearum
HostsQuercus spp.
VectorsNitidulidae
EPPO codeCERAFA
DistributionUS
Symptomsleaf discoloration, wilt, defoliation and death

Bretziella fagacearum
Spores produced by the oak wilt fungus (a) Endoconidia (b) Conidiophore
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Sordariomycetes
Order: Microascales
Family: Ceratocystidaceae
Genus: Bretziella
Species:
B. fagacearum
Binomial name
Bretziella fagacearum
(Bretz) Z.W. de Beer, Marincowitz, T.A. Duong & M.J. Wingfield[1]
USA counties with oak wilt (2017)
Synonyms
  • Chalara quercina[2]
  • Endoconidiophora fagacearum
  • Thielaviopsis quercina
  • Ceratocystis fagacearum[3][4]

Oak wilt is a fungal disease caused by the organism Bretziella fagacearum that threatens Quercus spp.[3] The disease is limited to the eastern half of the United States, and Southern Ontario. First described in the 1940s in the Upper Mississippi River Valley. The pathogen penetrates xylem tissue, preventing water transport and causing disease symptoms.[5] 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.[6] Moving firewood long distances can potentially transport diseases and invasive species.

Disease

[edit]
Photograph of leaf and whole tree symptoms of oak wilt in a red oak tree
Oak wilt symptoms
Photograph of red oak leaves on the ground in July
Sudden leaf drop
Root graft of hardwood tree after excavation following vibratory plowing
Excavated root graft
Close up of spore mat stage III
Spore mat

Oak wilt is a devastating exotic disease, killing some trees rapidly in a single season.[7] Oak wilt is an important disease in urban areas where trees are highly valued. The disease reduces property values because of the loss of trees and is economically costly to the property owner since they or the local government must pay for tree removal. Additionally, preventing the spread of the disease to healthy trees is costly and requires vigilance. Oak wilt is also an important disease in a forest setting, as entire forest stands can die within a few years.[8] There is a narrow window to salvage diseased trees for hardwood lumber and often the disease is not discovered within that logging window.[9] The ecological impacts to forests is also a concern. The disease is currently restricted to North America, but is potentially a serious threat to oaks worldwide.[10]

All Quercus spp. appear susceptible to the disease, with 33 oak species confirmed to be susceptible; including three species of Castanea, one species of Castanopsis, one species of Lithocarpus, and some oaks native to Europe (Q. petraea, Q. pubescens, & Q. robur).[11][12] Generally, red oaks (subsection Lobatae) display more severe symptoms with rapid and frequent mortality (particularly Q. velutina, Q. rubra, Q. ellipsoidalis & Q. coccinea). White oaks (subsection Quercus) develop symptoms more slowly, rarely die, and can recover from the pathogen with damage limited to a few branches (particularly Q. alba, & Q. macrocarpa). Live oaks (Q. fusiformis & Q. virginiana) display intermediate symptoms compared to red or white oaks. However, live oaks are semi-evergreen, can propagate vegetatively by root suckering, and cohabitate with other live oaks in dense stands enabling interconnected root systems. These traits are favorable for local spread of the disease in an oak-grassland savanna.[13]

History

[edit]

Oak wilt is one of three devastating North American vascular wilt diseases that appeared in the early 20th century. The other two vascular wilts are chestnut blight (1900–1950) and Dutch elm disease (1928–1980). Each of these diseases have depopulated their respective host tree populations. Chestnut trees were the dominant overstory tree species before chestnut blight and elms were an iconic landscape tree that bordered streets before Dutch elm disease. Oak wilt and the newly emerging emerald ash borer have the potential to devastate other important North American tree species with large geographical and cultural significance. Range expansion of oak wilt to the Western United States (or to other continents) is a major concern.

The asexual stage of oak wilt was first described in 1942 in Wisconsin.[14][15] Soon thereafter the disease was reported throughout the Upper Midwest and Central forests. The early 20th Century coincided with oak regeneration after significant logging in the Mid-Atlantic and Great Lakes region. Deforestation and fire suppression in this region altered the ecology to favor oak–hickory forests, instead of coniferous forests and grasslands.[16][17][18] Subsequently, the host for the disease became more prevalent and promoted oak wilt infections. Moving timber during the late 19th Century and early 20th Century, in the period of railroad expansion, coincides with the discovery of the oak wilt disease in the United States.

The origin of the disease is unknown, but probably emerged from Mexico, Central America, or South America.[19] Mexico is the global center of oak diversity, supporting it as the endemic range of oak wilt.[20][21] Any biocontrol or disease resistance for this pathogen will likely come from Mexico. The disease currently affects much of the eastern and central US, from northern New York to Central Texas.[22] It is particularly common in the Midwest where conditions are usually favorable for spore production and beetle activity during spring and early summer. Oak wilt is a major problem in Illinois, Iowa, Michigan, Minnesota, Texas, and Wisconsin.[23][24][25]

Disease cycle

[edit]
Oak wilt disease cycle
Illustration of the oak wilt disease cycle by Julie Martinez
Top cycle. Overland Spread (Initiation of new infection center).[12]
  • Spores germinate and infect oak tree.
  • Infection spreads throughout the tree and leaf symptoms develop. Discoloration develops in the vacular tissue.
  • Tree dies.
  • Fungal pressure pads and spore-bearing mats form under bark.
  • Nitidulids feed in pads and emerge with spores in and on their bodies.
  • Nitidulids visit fresh wounds on healthy oak and deposit spores.

Bottom cycle. Root graft Spread (Expansion of infection center).

  • Fungal spore move through grafted roots into adjacent uninfected trees.
  • Healthy tree becomes infected.
Illustration of Bretziella fagacearum
Photograph of Bretziella fagacearum

The fungus overwinters on dead tissue from diseased trees. Symptoms first appear in spring and summer. Highly susceptible species typically die within one year (often within six weeks) after symptoms appear. Symptoms begin in the tops of trees and can be difficult to notice. The disease progresses inward and downward from the tree top. Leaves become chlorotic beginning at the leaf tip and leaf edges. An abrupt demarcation of chlorotic veins and green tissue is often a distinguishing characteristic in live oak infections.[26] The foliage may droop, curl lengthwise, wilt, and begin to fall. Leaves drop from the tree in the middle of summer, however less susceptible trees may retain leaves longer and resemble seasonal autumn foliage. Highly susceptible species will exhibit rapid crown dieback, while less susceptible species may only lose a few scattered branches. Live oaks may survive several years with progressive dieback, but often die within six months. Following defoliation, fungal fruiting bodies develop from mycelium under the bark of the tree. The mats grow to 10 – 20 cm in size, elliptical in shape, and grey in color with white margins that darken with age. These mats are not found on live oaks and rarely on white oaks. Trees capable of producing mats are called potential spore-producing trees (PSPT). Brown streaks in the sapwood is also observed in the oak wilt disease. However, this symptom is not always associated with the disease.

The oak wilt fungus can spread from diseased trees to healthy trees in several ways. The disease can spread long distances (overland) by airborne spores in open wounds caused by wind damage, pruning, or other mechanical damage. Alternatively, under ideal conditions (temperature, moisture content, wood pH) spore mats form under the bark of the dead tree. Spore mats develop in the spring or fall for 2–3 weeks. The center of spore mats produce chains of barrel shaped spores, called endoconidia. Conidia are asexual spores dispersed by air, rain, and insects.[27] If compatible mating types are present, these mats will also produce sexual spores called ascospores in fruiting structures called perithecia. Ascospores are spread by water and insects.[27] These spore mats (or pressure pads) increase in size, eventually breaking through the bark and releasing a fruity odor that attracts wildlife, including sap beetles, bark beetles, other insects, birds and animals, such as squirrels. Insect vectors transmit the disease in spring to early summer in the Mid-West and late Winter in Texas. Insect transmission is the primary way new infection foci originate.

The fungus can spread short distances through naturally occurring root grafts. Root grafts form when two or more underground roots merge from adjacent trees. Typically, roots from the same, or similar species, can form root grafts as their cambia are pressed together and combine.[28][29] Fungal spores in the xylem travel to nearby trees through these root grafts and can rapidly kill many trees simultaneously. This transmission method accounts for the vast majority of infections and is particularly devastating as groups of trees are killed. The disease can extend 10 – 20m per year (40m per year in Texas) from the infection foci to surrounding trees. Diseased trees can continue to harbor and transmit the disease for several years through the root network.

The disease results from fungal spores clogging xylem vessels and preventing water and nutrient flow. Mycelia growth between and through vessels end up blocking xylem pits in the vessel endwalls. Tylose protrusion and the accumulation of 'gums' will further obstruct vessels. Tylose is an outgrowth of parenchyma cells created as a plant defense against pathogens, water deficiency, wounding, and heartwood formation. Tylose formation signals senescence of adjacent parenchyma cells and secretion of secondary metabolites (called gums), which may include phenolics.[30] The interruption of the xylem vessels precedes tylose formation. Tylose and secreted gums act as a barrier to slow the colonization of the pathogen and play an important part in plant defenses. However, the action to compartmentalize the oak wilt fungus ultimately obstructs all water conductance, leading to death. The fungus can survive in the xylem for multiple years, if the tree is not killed.

Oak Wilt Management Quick Guide

Early detection and prompt action are essential for successful management of oak wilt. The specific measures taken depend on several circumstances but should include appropriate combinations of the following:

  • Prevent New Infections
    • Remove and dispose of oak wilt-infected red oaks immediately.
    • Avoid wounding oak trees, including pruning from,
      • February through June in Texas.
      • April through October in the Mid-West.
    • Sterilize/sanitize all pruning equipment between trees.
    • Paint all wounds and fresh stumps immediately regardless of season.
    • Handle oak firewood cautiously, burn all firewood before spring, and never store unseasoned oak wood from infected trees near healthy oaks.
    • Cover unseasoned firewood (from infection centers and unknown origins) with clear plastic and bury the edges of the plastic.
  • Diversify Your Landscape
    • Plant trees that are native and/or adapted to your area.
    • Favor a diversity of tree species.
    • Avoid wounding oaks during planting.
  • Stop Spread through Root Connections
    • Install a trench at least 4 ft deep and 100 ft beyond the perimeter of infection centers (last symptomatic tree) to break up root connections.
    • Cut or uproot all trees within the 100-ft barrier (except those injected with fungicide).
  • Inject High-Value Oaks with Fungicide
    • Identify susceptible, high-value oak trees in proximity to expanding oak wilt infection centers.
    • Consult a trained and licensed arborist (with certified applicator's license) for treatment of susceptible trees with injections of propiconazole.

Management

[edit]
Photograph of person pointing to spore mat
Wood caramel colored, spore mats stage III is infectious
Photograph of dead tree trunk
Spore mats (dark patches) stage IV – V are no longer infectious

Elimination of the disease is not possible; therefore, managing the disease is essential to prevent economic and ecological losses.[citation needed] Management of the oak wilt disease includes forest integrated pest management; such as sanitation, chemical application, and cultural control. Ideally, several methods are used in conjunction to enhance disease control. Any chosen method relies on specific landowner objectives; such as protecting high value trees, treating individual trees, halting or slowing the spread of an infection center, and reducing the number of new infection foci. All methods depend on timely detection and accurate diagnosis of the disease to be beneficial. Aerial observation (or remote sensing) is able to identify infected forest stands by observing the dead crowns of trees in summer. The use of spectroscopy is being developed for large scale detection and monitoring of oak wilt.[31]

Chemical control

[edit]

Chemical control can be preventative or therapeutic, depending on risk and resources available. Propiconazole is the principle fungicide for treatment against oak wilt. Propiconazole is a broad-spectrum systemic fungicide that interferes with the biosynthesis of ergosterol in cell membranes by binding to 14 alpha-demethylase. Tree injection is the preferred application method to deliver targeted control. Tree injections involve intravascular injections with positive pressure to force the chemical throughout the vascular system of the tree. This method is relatively expensive and requires a trained arborist to perform .[32][33] Propiconazole injection does not offer protection to neighboring trees and must be applied to all target trees.

Preventative propiconazole application does not prevent infection, rather it delays symptoms and reduces mortality. All oak species studied have benefited from preventative propiconazole treatment.[11] This method is often applied to high value trees in an urban area, specifically Northern red oaks and live oaks. White oaks are more disease resistant, thus preventative treatment is unnecessary. Likewise, therapeutic propiconazole application does not eradicate the fungal infection, rather it delays symptoms and reduces mortality. Highly susceptible red oaks rarely benefit from therapeutic treatment, but symptomatic white oaks improve with treatment. Asymptomatic live oaks will respond better to propiconazole treatment than symptomatic trees.

Spring application is the most effective time for chemical treatment. Multiple applications, every two years, may be necessary for long-term disease control.

Cultural Control

[edit]

Mechanical

[edit]

Mechanical separation of the underground root connections will not allow the disease to transfer to adjacent trees. However, ensuring all root connections are severed is difficult and impractical to verify. Notwithstanding, digging a trench (or plowline) four feet deep around infected trees is an effective cultural control strategy. The plowline should encompass any infected tree. In practice this consists of all trees expected to be connected by a root graft with an infected tree, in addition to all symptomatic trees. In the Mid-West, a plowline 50 feet away from infected trees is recommended. In Central Texas, live oak lateral roots grow at a shallow depth in rocky soil, allowing an extensive root network with neighboring trees. For this reason, a plowline 100 feet away from infected trees is recommended.[13] A second plowline between all symptomatic trees and visibly healthy trees will reinforce this control strategy.

The plowline can be created with agricultural machinery, such as an excavator, rock saw, vibratory plow, and bulldozer with ripper or subsoiler. Equipment costs and availability will vary.

The placement of a root barrier can offer additional protection to trenching, but increases total costs. A geomembrane is a semipermeable textile (similar to landscape fabric) that physically blocks roots from coming into contact. It is essential that trenching and geomembrane installation occur before removing infected trees.

Sanitation

[edit]
Oak wilt and buckthorn cleanup on oak savanna in Chisago County, Minnesota autumn/after leaf drop 2007
Cultural control (sanitation) of oak wilt infection area

Sanitation entails removing infectious material to reduce inoculum before new infections can develop. Red oaks are the only group capable of forming spore mats, designated as PSPTs. Therefore, removing any PSPTs that become infected is essential to minimize new infection foci. Furthermore, removing all PSPTs, regardless of symptoms, within an infected area reinforces the process. In practice this consists of removing all PSPTs within the plowline (see Mechanical). Trees will need to be removed annually to sustain control over the years. Tree removal involves felling and burying or burning the logs, ensuring all inoculum is discarded. Alternatively, logs and slash can be chipped or mulched on site. Tree stumps can also be removed to increase sanitation.

Girdling infected trees is another method to reduce the spread of oak wilt; although, not as effective as whole tree removal. Girdling requires the complete detachment of the cambium from the PSPTs. Moreover, debarking the trunk of the tree (up to 4 feet) is essential. Oak wilt does not produce fruiting bodies on dead or dry wood. Debarking speeds the drying process and assists Hypoxylon coccineum in colonizing the wood.

Sap beetles are opportunistic insects, incapable of penetrating a tree without an open wound. Therefore, avoid pruning or felling oak trees when fungal spores and beetles are active. In the Mid-West avoid injuring oaks from April to October and prune limbs after the first hard frost, or from November until April. In Texas avoid pruning oaks from February through June. Moreover, clean pruning equipment between each tree and apply tree paint to any injury or open wound. Injuries often occur during construction and severe weather.

Silviculture

[edit]

Silviculture involves keeping a forest healthy. Typically, a healthy forest with healthy trees will be more resistant to pests and diseases. Thinning is the process of removing unwanted trees to promote the growth of the desired trees. Oaks are shade intolerant species. Releasing (or thinning) oaks from competition provides more light, moisture, and nutrients to the remaining oaks. Overall the oaks become stronger, more healthy, and more capable to resist pests and disease.

Increasing tree species diversity (i.e. species evenness) in a forest is another method to lessen the impact of the disease. Evidence shows increasing diversity in a landscape can increase forest resilience to pests and disease.[34][35][36][37] Moreover, increasing diversity can increase soil microbial communities and ecosystem services.[38][39][40][41][42]

Education

[edit]

Education is the most valuable tool to combat the spread of pests and diseases. In this context, warning the public about the spread of oak wilt by humans. Specifically, people take fuelwood from one location to another location, often long distances. This action is responsible for moving pathogens in those logs to places they are not currently present. Spreading oak wilt to new locations through firewood is a major problem. Moreover, covering firewood with clear plastic can solarize the wood pile and eradicate any pathogens.

Prevent the spread of invasive species and diseases

  • Don't take firewood with you on your camping trip, RV adventure, or to your hunting camp.
  • Don't bring firewood back from your second home to your place in the suburbs.
  • Buy firewood near where you will burn it, or gather firewood on site when permitted.
    • A good rule of thumb is only using wood that was cut within 50 miles of where you'll have your fire.
  • Certified heat-treated firewood is safe to move long distances.
  • Aged or seasoned wood is still not safe.
    • Just because it is dry doesn't mean that bugs can't crawl onto it- and some insects can take several years to mature inside the wood.
    • Wood that looks clean and healthy can still have tiny insect eggs, or microscopic fungi spores, that will start a new and deadly infestation.
  • North Flank of 7 January 2011 Windstorm went thru northern Pine and Carlton Counties Minnesota. Photo shows hilltop infections from 24–25 May 2016 wind & hailstorms; spores came from 7-1-11 storm-created infection center near Kerrick, Minnesota
    Infected trees
  • South Flank of 7 January 2011 Windstorm went thru St. Croix County, Wisconsin. Photo shows one of five 7-1-11 infection centers on hilltop near East Farmington, Wisconsin
    Infection foci on hilltop
  • Healthy white oak (Q. alba) remaining after cleaning up 7-1-11 storm damage & oak wilt infections, 13 months after storm, 2012, Chisago County Minnesota
    White oak after storm damage
  • Northern Pin Oak overland Infection on field edge from 1 July 2011 Windstorm, West of Grasston, Kanabec County, Minnesota
    Northern pin oak overland infection

See also

[edit]

References

[edit]
  1. ^ "Bretziella fagacearum(CERAFA)". gd.eppo.int. Secretariat of the European and Mediterranean Plant Protection Organization. Retrieved 5 November 2020.
  2. ^ de Beer, Z. Wilhelm; Marincowitz, Seonju; Duong, Tuan A.; Wingfield, Michael J. (28 August 2017). "Bretziella, a new genus to accommodate the oak wilt fungus, Ceratocystis fagacearum (Microascales, Ascomycota)". MycoKeys (27): 1–19. doi:10.3897/mycokeys.27.20657. hdl:2263/63081. Retrieved 5 November 2020.
  3. ^ a b Sinclair, Wayne; Lyon, Howard H. (2005). Diseases of Trees and Shrubs. Comstock Publishing Associates. p. 238. ISBN 9780801443718.
  4. ^ According to Species Fungorum, the current name is Ceratocystis fagacearum: "the Ceratocystis fagacearum page". Species Fungorum. Royal Botanic Gardens Kew. Retrieved 16 May 2021.
  5. ^ "Oak Wilt". mortonarb.org. The Morton Arboretum. Retrieved 5 November 2020.
  6. ^ Liebhold, Andrew H.; MacDonald, William L.; Bergdahl, Dale; Mastro, Victor C. (1995). "Invasion by Exotic Forest Pests: A Threat to Forest Ecosystems" (PDF). Forest Science Monographs. 30. The Society of American Foresters: 49. Retrieved 5 November 2020.
  7. ^ David Appel (8 July 2008). Oak Wilt Identification and Management (YouTube). Archived from the original on 13 December 2021. Retrieved 15 November 2020.
  8. ^ Guo, Qinfeng; Fei, Songlin; Kevin M., Potter; Andrew M., Liebhold; Wen., Jun (2019). "Invasion by Exotic Forest Pests: A Threat to Forest Ecosystems" (PDF). Proceedings of the National Academy of Sciences. 116 (15): 7382–7386. doi:10.1073/pnas.1821039116. PMC 6462093. PMID 30910953. Retrieved 5 November 2020.
  9. ^ Horie, Tetsuya; Haight, Robert G.; Homans, Frances R.; Venette, Robert C. (30 September 2012). "Optimal strategies for the surveillance and control of forest pathogens: A case study with oak wilt". Ecological Economics. 86: 78–85. doi:10.1016/j.ecolecon.2012.09.017. S2CID 85722498. Retrieved 5 November 2020.
  10. ^ "Oak wilt (Ceratocystis fagacearum)". forestresearch.gov.uk. Forest Commission (UK). Retrieved 19 October 2020.
  11. ^ a b Koch, Karrie A.; Quiram, Gina L.; Venette, Robert C. (2010). "A review of oak wilt management: A summary of treatment options and their efficacy" (PDF). Urban Forestry & Urban Greening. 9 (1). Elsevier GmbH: 1–8. Bibcode:2010UFUG....9....1K. doi:10.1016/j.ufug.2009.11.004. Retrieved 5 November 2020.
  12. ^ a b Juzwik, Jennifer (2000). "An oak wilt primer". International Oaks. 11. The Journal of the International Oak Society: 14–20.
  13. ^ a b Appel, DN (1995). "The Oak Wilt Enigma: Perspectives from the Texas Epidemic". Annual Review of Phytopathology. 33. Annual Reviews: 103–118. doi:10.1146/annurev.py.33.090195.000535. PMID 18288898. Retrieved 5 November 2020.
  14. ^ Henry, BW (1944). "Chalara qercina n. sp., the cause of oak wilt". Phytopathology. 34: 631–635.
  15. ^ Bretz, TW (1953). "Oak wilt: a new threat". USDA Yearbook of Agriculture 1953: 851–855.
  16. ^ "Historical ecology of the upper midwest". nrs.fs.fed.us. USFS Northern Research Station. 2006. Archived from the original on 2 July 2017. Retrieved 19 October 2020.
  17. ^ Van Sambeek JW, Dawson JO, Ponder F Jr, Loewenstein EF, Fralish JS (2003). "The Central Hardwood Forest: Its Boundaries and Physiographic Provinces". Proceedings of the 13th Central Hardwood Forest Conference. 234. U.S. Department of Agriculture, Forest Service, North Central Research Station.
  18. ^ Johnson, Paul S. (1992). "Perspectives on the ecology and silviculture of oak-dominated forests in the Central and Eastern States". nrs.fs.fed.us. USFS Northern Research Station. Retrieved 19 October 2020.
  19. ^ Juzwik J, Harrington TC, MacDonald WL, Appel DN (2008). "The origin of Ceratocystis fagacearum, the oak wilt fungus". Annual Review of Phytopathology. 46: 13–26. doi:10.1146/annurev.phyto.45.062806.094406. PMID 18680421.
  20. ^ Fallon B, Yang A, Lapadat C, Armour I, Juzwik J, Montgomery RA, and Cavender-Bares J (2018). "Sympatric parallel diversification of major oak clades in the Americas and the origins of Mexican species diversity". New Phytologist. 217 (1). John Wiley & Sons, Inc.: 439–452. doi:10.1111/nph.14773. PMID 28921530.
  21. ^ Hipp AL, Manos PS, Hahn M, Avishai M, Bodénès C, Valencia-Avalos S (2019). "Genomic landscape of the global oak phylogeny". New Phytologist. 226 (4). John Wiley & Sons, Inc.: 1198–1212. doi:10.1111/nph.16162. PMID 31609470.
  22. ^ "Oak Wilt". dec.ny.gov. NYS Dept. of Environmental Conservation.
  23. ^ Nelson, Steven Floyd (2011). Savanna Soils of Minnesota: A Comprehensive Inventory by County and Soil Series. Steven Floyd Nelson. pp. 21–22, 29–30. ISBN 978-0-615-50320-2.
  24. ^ Wisconsin DNR Division of Forestry, Annual Report 2012 p. 6
  25. ^ Cigan, Paul; Williams, Linda (3 December 2008). "New northern oak wilt detections". forestrynews.blogs.govdelivery.com.
  26. ^ "How to identify and manage oak wilt in Texas" (PDF). Texasokwilt.org. Texas A&M Forest Service. June 2003. Retrieved 12 June 2017.
  27. ^ a b Käärik, A. (1983). Nilsson, Siwert (ed.). Atlas of Airborne Fungal Spores in Europe. Berlin, Heidelberg, New York: Springer-Verlag. p. 7. doi:10.1007/978-3-642-68803-4. ISBN 978-3-642-68803-4. S2CID 12449840.
  28. ^ Lev-Yadun, Simcha; Sprugel, Douglas (June 2011). "Why should trees have natural root grafts?". Tree Physiology. 31 (6). Oxford University Press: 575–578. doi:10.1093/treephys/tpr061. PMID 21778291.
  29. ^ Lagomarsino, Valentina (6 May 2019). "Exploring The Underground Network of Trees – The Nervous System of the Forest". sitn.hms.harvard.edu. Harvard University. Retrieved 19 October 2020.
  30. ^ Rioux, D.; Nicole, M.; Simard, M.; Ouellette, G.B. (1998). "Immunocytochemical Evidence that Secretion of Pectin Occurs During Gel (Gum) and Tylosis Formation in Trees". Phytopathology. 88 (6). The American Phytopathological Society: 494–505. doi:10.1094/PHYTO.1998.88.6.494. PMID 18944900.
  31. ^ Fallon B, Yang A, Lapadat C, Armour I, Juzwik J, Montgomery RA, and Cavender-Bares J (2020). "Spectral differentiation of oak wilt from foliar fungal disease and drought is correlated with physiological changes". Tree Physiology. 40 (3). Oxford University Press: 377–390. doi:10.1093/treephys/tpaa005. PMID 32031662.
  32. ^ Shawn Bernick (10 April 2015). Webinar: Management of Oak Wilt in Urban Areas (YouTube). Rainbow Tree Service. Archived from the original on 13 December 2021. Retrieved 15 November 2020.
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