Oak wilt is a

fungal A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the tradit ...

disease caused by the

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

''Bretziella fagacearum'' that threatens ''Quercus'' spp. The disease is limited to the eastern half of the United States, Central Texas, and Southern Ontario. First described in the 1940s in the Upper Mississippi River Valley. The

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

penetrates

xylem Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...

tissue, preventing water transport and causing disease symptoms. Symptoms generally consist of leaf discoloration, wilt,

defoliation A defoliant is any Herbicide, herbicidal chemical sprayed or dusted on plants to cause their Leaf, leaves to fall off. Defoliants are widely used for the selective removal of weeds in managing croplands and lawns. Worldwide use of defoliants, ...

, and death. The disease is dispersed by insect vectors and to adjacent trees through underground root networks. However, human spread is the most consequential dispersal method. Moving firewood long distances can potentially transport diseases and invasive species.

Disease

Oak wilt is a devastating exotic disease, killing some trees rapidly in a single season. Oak wilt is an important disease in

urban areas An urban area is a human settlement with a high population density and an infrastructure of built environment. Urban areas originate through urbanization, and researchers categorize them as cities, towns, conurbations or suburbs. In urbani ...

where trees are highly valued. The disease reduces property values because of the loss of trees and is economically costly to the

property owner In property law, title is an intangible construct representing a bundle of rights in a piece of property in which a party may own either a legal interest or equitable interest. The rights in the bundle may be separated and held by different part ...

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. There is a narrow window to salvage diseased trees for

hardwood Hardwood is wood from Flowering plant, angiosperm trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal ecosystem, boreal latitudes they are mostly deciduous, but in tropics and subtropics mostl ...

lumber Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). ...

and often the disease is not discovered within that logging window. The

ecological Ecology () is the natural science of the relationships among living organisms and their environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere levels. Ecology overlaps with the closely re ...

impacts to forests is also a concern. The disease is currently restricted to North America, but is potentially a serious threat to oaks worldwide. 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 ''Castanopsis'', commonly called chinquapin or chinkapin, is a genus of evergreen trees belonging to the beech family, Fagaceae. The genus contains about 140 species, which are today restricted to tropical and subtropical eastern Asia. The Engli ...

'', one species of ''

Lithocarpus ''Lithocarpus'' is a genus in the beech family, Fagaceae. Trees in this genus are commonly known as the stone oaks and differ from ''Quercus'' primarily because they produce insect-pollinated flowers on erect spikes and the female flowers hav ...

'', and some oaks native to Europe ( ''Q. petraea'', ''Q. pubescens'', & ''Q. robur''). 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.

History

Oak wilt is one of three devastating North American vascular

wilt disease A wilt disease is any number of diseases that affect the vascular system of plants. Attacks by fungi, bacteria, and nematodes can cause rapid killing of plants, large tree branches or even entire trees. Wilt diseases in woody plants tend to fal ...

s that appeared in the early 20th century. The other two vascular wilts are

chestnut blight The pathogenic fungus ''Cryphonectria parasitica'' (formerly ''Endothia parasitica'') is a member of the Ascomycota (sac fungi). This necrotrophic fungus is native to East Asia and South East Asia and was introduced into Europe and North America ...

(1900–1950) and Dutch elm disease (1928–1980). Each of these diseases have depopulated their respective host tree populations.

Chestnut The chestnuts are the deciduous trees and shrubs in the genus ''Castanea'', in the beech family Fagaceae. The name also refers to the edible nuts they produce. They are native to temperate regions of the Northern Hemisphere. Description ...

trees were the dominant

overstory In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, the canopy is the upper layer or habitat zone, formed by mature tree crowns and includ ...

tree species before chestnut blight and

elm Elms are deciduous and semi-deciduous trees comprising the genus ''Ulmus'' in the family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical- montane regions of North America and Eurasia, ...

s were an iconic

landscape A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or human-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes th ...

tree that bordered streets before Dutch elm disease. Oak wilt and the newly emerging

emerald ash borer The emerald ash borer (''Agrilus planipennis''), also known by the abbreviation EAB, is a green buprestid or jewel beetle native to north-eastern Asia that feeds on ash trees, ash species (''Fraxinus'' spp.). Females lay eggs in bark crevices o ...

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 A continent is any of several large geographical regions. Continents are generally identified by convention rather than any strict criteria. A continent could be a single large landmass, a part of a very large landmass, as in the case of As ...

) is a major concern. The asexual stage of oak wilt was first described in 1942 in Wisconsin. Soon thereafter the disease was reported throughout the

Upper Midwest The Upper Midwest is a northern subregion of the U.S. Census Bureau's Midwestern United States. Although the exact boundaries are not uniformly agreed upon, the region is usually defined to include the states of Iowa, Michigan, Minnesota and Wi ...

and Central forests. The early

20th Century The 20th century began on 1 January 1901 (MCMI), and ended on 31 December 2000 (MM). It was the 10th and last century in the 2nd millennium and was marked by new models of scientific understanding, unprecedented scopes of warfare, new modes of ...

coincided with oak regeneration after significant logging in the Mid-Atlantic and

Great Lakes region The Great Lakes region of Northern America is a binational Canadian– American region centered on the Great Lakes that includes the U.S. states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin and the Ca ...

Deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...

and fire suppression in this region altered the ecology to favor

oak–hickory forest Oak–hickory forest is a type of North American forest ecosystem, and an ecoregion of the Temperate broadleaf and mixed forests Biome. Geography It has a range extending from Rhode Island and southern New York, west to Iowa, and south to Northern ...

s, instead of coniferous forests and

grasslands A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes such as clover, and other herbs. Grasslands occur ...

. 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. Mexico is the global center of oak diversity, supporting it as the endemic range of oak wilt. Any

biocontrol Biological control or biocontrol is a method of pest control, controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or phytopathology, plants by bioeffector, using other organisms. It relies o ...

disease resistance Disease resistance is the ability to prevent or reduce the presence of diseases in otherwise susceptible hosts. It can arise from genetic or environmental factors, such as incomplete penetrance. Disease tolerance is different as it is the abilit ...

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 Central Texas is a region in the U.S. state of Texas roughly bordered on the west by San Saba, to the southeast by Bryan- College Station, the south by San Marcos and to the north by Hillsboro. Central Texas overlaps with and includes part ...

. It is particularly common in the

Midwest The Midwestern United States (also referred to as the Midwest, the Heartland or the American Midwest) is one of the four census regions defined by the United States Census Bureau. It occupies the northern central part of the United States. It ...

where conditions are usually favorable for spore production and beetle activity during spring and early summer. Oak wilt is a major problem in

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

Iowa Iowa ( ) is a U.S. state, state in the upper Midwestern United States, Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Ill ...

Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...

Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, and

Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...

Disease cycle

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 Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal c ...

and green tissue is often a distinguishing characteristic in live oak infections. 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 A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, parti ...

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

, fungal

fruiting bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...

develop from

mycelium Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...

under the

bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...

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 A wound is any disruption of or damage to living tissue, such as skin, mucous membranes, or organs. Wounds can either be the sudden result of direct trauma (mechanical, thermal, chemical), or can develop slowly over time due to underlying diseas ...

caused by wind damage,

pruning Pruning is the selective removal of certain parts of a plant, such as branches, buds, or roots. It is practiced in horticulture (especially fruit tree pruning), arboriculture, and silviculture. The practice entails the targeted removal of di ...

, 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 A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

are asexual spores dispersed by air, rain, and insects. If compatible mating types are present, these mats will also produce sexual spores called ascospores in fruiting structures called

perithecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascoc ...

Ascospores In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse division of fungi. After two parental nuclei fuse, the ascus undergoes meiosis (halving of ...

are spread by water and insects. 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 A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct Family (biology), family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculioni ...

, 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 In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

grafts. Root

grafts Grafting refers to a surgical procedure to move tissue from one site to another on the body, or from another creature, without bringing its own blood supply with it. Instead, a new blood supply grows in after it is placed. A similar techniqu ...

form when two or more underground roots merge from adjacent trees. Typically,

s from the same, or similar species, can form root grafts as their

cambia Cambia is an Australian-based global non-profit social enterprise focusing on open science, biology, innovation system reform and intellectual property. Its projects include The Lens, formerly known as Patent Lens, and the Biological Innovat ...

are pressed together and combine. Fungal spores in the

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

vessels and preventing water and nutrient flow.

Mycelia Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...

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 upright=1.6, Lung parenchyma showing damage due to large subpleural bullae. Parenchyma () is the bulk of functional substance in an animal organ such as the brain or lungs, or a structure such as a tumour. In zoology, it is the tissue that ...

cells created as a plant defense against pathogens, water deficiency, wounding, and

heartwood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

formation. Tylose formation signals senescence of adjacent parenchyma cells and secretion of

secondary metabolites Secondary metabolites, also called ''specialised metabolites'', ''secondary products'', or ''natural products'', are organic compounds produced by any lifeform, e.g. bacteria, archaea, fungi, animals, or plants, which are not directly involved ...

(called gums), which may include phenolics. 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.

Management

Elimination of the disease is not possible; therefore, managing the disease is essential to prevent economic and ecological losses. 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 {{Unreferenced, date=March 2018 In general, detection is the action of accessing information without specific cooperation from with the sender. In the history of radio communications, the term "detector" was first used for a device that detected ...

and accurate diagnosis of the disease to be beneficial. Aerial observation (or

remote sensing Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring inform ...

) is able to identify infected forest stands by observing the dead crowns of trees in summer. The use of

spectroscopy Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...

is being developed for large scale detection and monitoring of oak wilt.

Chemical control

Chemical control can be preventative or therapeutic, depending on risk and resources available. Propiconazole is the principle

fungicide Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, resulting in losses of yield and quality. Fungicides are used both in agriculture and to fight fungal infections in animals, ...

for treatment against oak wilt. Propiconazole is a broad-spectrum systemic fungicide that interferes with the

biosynthesis Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-Catalysis, catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthe ...

ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a mycosterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many fungi and protozoa cannot survive without ergostero ...

cell membranes The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extra ...

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 Positive pressure is a pressure within a system that is greater than the environment that surrounds that system. Consequently, if there is any leak from the positively pressured system, it will egress into the surrounding environment. This is in ...

to force the chemical throughout the vascular system of the tree. This method is relatively expensive and requires a trained

arborist An arborist, or (less commonly) arboriculturist, is a professional in the practice of arboriculture, which is the Plant cultivation, cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants in dend ...

to perform . 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. 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

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

live oak Live oak or evergreen oak is any of a number of oaks in several different sections of the genus ''Quercus'' that share the characteristic of evergreen foliage. These oaks are generally not more closely related to each other than they are to o ...

lateral roots Lateral roots, emerging from the pericycle (meristematic tissue), extend horizontally from the primary root (radicle) and over time makeup the iconic branching pattern of root systems. They contribute to anchoring the plant securely into the soil ...

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. A second plowline between all symptomatic trees and visibly healthy trees will reinforce this control strategy. The plowline can be created with

agricultural machinery Agricultural machinery relates to the machine (mechanical), mechanical structures and devices used in farming or other agriculture. There are list of agricultural machinery, many types of such equipment, from hand tools and power tools to tractor ...

, such as an

excavator Excavators are heavy equipment (construction), heavy construction equipment primarily consisting of a backhoe, boom, dipper (or stick), Bucket (machine part), bucket, and cab on a rotating platform known as the "house". The modern excavator's ...

, rock saw, vibratory plow, and bulldozer with ripper or

subsoiler A subsoiler or flat lifter is a tractor-mounted farm implement used for deep tillage, loosening and breaking up soil at depths below the levels worked by moldboard ploughs, disc harrows, or rototillers. Most such tools will break up and turn ove ...

. Equipment costs and availability will vary. The placement of a root barrier can offer additional protection to trenching, but increases total costs. A

geomembrane A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (liquid or gas) migration in a human-made project, structure, or system. Geomembranes are m ...

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

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 Mechanical may refer to: Machine * Machine (mechanical), a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement * Mechanical calculator, a device used to perform the basic operations o ...

). Trees will need to be removed annually to sustain control over the years. Tree removal involves

felling Felling is the process of cutting down trees,"Feller" def. 2. and "Felling", def. 1. ''Oxford English Dictionary'' 2nd ed. via CD-ROM (v. 4.0) © Oxford University Press. 2009. an element of the task of logging. The person cutting the trees is ...

and burying or burning the logs, ensuring all inoculum is discarded. Alternatively, logs and

slash Slash may refer to: * Slash (punctuation), the "/" character Arts and entertainment Fictional characters * Slash (Marvel Comics) * Slash (''Teenage Mutant Ninja Turtles'') Music * Harry Slash & The Slashtones, an American rock band * Nash th ...

can be chipped or

mulch A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving soil fertility, fertility and health of the soil, reducing Weed control, weed growth, and enhancing the v ...

ed on site. Tree stumps can also be removed to increase sanitation.

Girdling Girdling, also called ring-barking, is the circumferential removal or injury of the bark (consisting of cork cambium or "phellogen", phloem, cambium and sometimes also the xylem) of a branch or trunk of a woody plant. Girdling prevents th ...

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 A cambium (: cambiums or cambia), in plants, is a tissue layer that provides partially undifferentiated cells for plant growth. It is found in the area between xylem and phloem. A cambium can also be defined as a cellular plant tissue from whic ...

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

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 A wound is any disruption of or damage to living tissue, such as skin, mucous membranes, or organs. Wounds can either be the sudden result of direct trauma (mechanical, thermal, chemical), or can develop slowly over time due to underlying diseas ...

. Injuries often occur during construction and

severe weather Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. These vary depending on the latitude, altitude, topography, and atmospheric conditions. High ...

Silviculture

Silviculture Silviculture is the practice of controlling the growth, composition/structure, as well as quality of forests to meet values and needs, specifically timber production. The name comes from the Latin ('forest') and ('growing'). The study of forests ...

involves keeping a forest healthy. Typically, a healthy forest with healthy trees will be more resistant to pests and diseases.

Thinning In agricultural sciences, thinning is the removal of some plants, or parts of plants, to make room for the growth of others. Selective removal of parts of a plant such as branches, buds, or roots is typically known as '' pruning''. In forestry ...

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 Species diversity is the number of different species that are represented in a given community (a dataset). The effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundan ...

(i.e. species evenness) in a forest is another method to lessen the impact of the disease. Evidence shows increasing

diversity Diversity, diversify, or diverse may refer to: Business *Diversity (business), the inclusion of people of different identities (ethnicity, gender, age) in the workforce *Diversity marketing, marketing communication targeting diverse customers * ...

in a landscape can increase forest resilience to pests and disease. Moreover, increasing diversity can increase soil microbial communities and

ecosystem service Ecosystem services are the various benefits that humans derive from ecosystems. The interconnected living and non-living components of the natural environment offer benefits such as pollination of crops, clean air and water, decomposition of wast ...

Education

Education is the most valuable tool to combat the spread of pests and diseases. In this context, warning the

public In public relations and communication science, publics are groups of individual people, and the public (a.k.a. the general public) is the totality of such groupings. This is a different concept to the sociology, sociological concept of the ''Öf ...

about the spread of oak wilt by humans. Specifically, people take

fuelwood Firewood is any wooden material that is gathered and used for fuel. Generally, firewood is not heavily processed, and is in some sort of recognizable log or branch form, compared to other forms of wood fuel like pellets. Firewood can be se ...

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 Firewood is any wooden material that is gathered and used for fuel. Generally, firewood is not heavily processed, and is in some sort of firelog, recognizable log or branch form, compared to other forms of wood fuel like pellet fuel, pellets. ...

with clear plastic can solarize the wood pile and eradicate any pathogens.

References

External links

How to Identify, Prevent and Control Oak Wilt

Texas Oak Wilt

Oak Wilt - Identify Common Oak Wilt Symptoms

Texas A&M Forest Service FAQ

Canadian Forest Invasives – Oak Wilt
{{Taxonbar, from=Q1991788, from2=Q99224441 Parasitic fungi Fungal tree pathogens and diseases Quercus Fungi of Central America Fungi of North America Fungi of South America