Forest pathology is the research of both biotic and abiotic maladies affecting the health of a

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

, primarily fungal pathogens and their insect vectors. It is a subfield of

forestry Forestry is the science and craft of creating, managing, planting, using, conserving and repairing forests and woodlands for associated resources for human and Natural environment, environmental benefits. Forestry is practiced in plantations and ...

and

plant pathology Plant pathology or phytopathology is the scientific study of plant diseases caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Plant pathology involves the study of pathogen identification, disease ...

. Forest

pathology Pathology is the study of disease. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatme ...

is part of the broader approach of forest protection. Insects, diseases and severe weather events damaged about 40 million ha of forests in 2015, mainly in the temperate and boreal domains.

Abiotic factors

There are a number of abiotic factors which affect the health of a forest, such as moisture issues like

drought A drought is a period of drier-than-normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, ...

, winter-drying, waterlogging resulting from over-abundance or lack of

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

such as

hail Hail is a form of solid Precipitation (meteorology), precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailsto ...

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

rain Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...

. Wind is also an important abiotic factor as

windthrow In forestry, windthrow refers to trees uprooted by wind. Breakage of the tree bole (botany), bole (trunk) instead of uprooting is called windsnap. Blowdown refers to both windthrow and windsnap. Causes Windthrow is common in all forested ...

(the uprooting or breaking of trees due to high winds) causes an obvious and direct loss of stability to a forest or its trees. Often, abiotic factors and biotic factors will affect a forest at the same time. For example, if wind speed is 80 km per hour then many trees which have

root rot Root rot is a condition in which anoxic conditions in the soil or potting media around the roots of a plant cause them to rot. This occurs due to excessive standing water around the roots.-Hydroponics Root Rot: What is It, How To Treat It, How ...

(caused by a pathogen) are likely to be thrown. Higher wind speeds are necessary to damage healthier trees.

Fire Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. Flames, the most visible portion of the fire, are produced in the combustion re ...

, whether caused by humans or

lightning Lightning is a natural phenomenon consisting of electrostatic discharges occurring through the atmosphere between two electrically charged regions. One or both regions are within the atmosphere, with the second region sometimes occurring on ...

, and related abiotic factors also affect the health of forest. The effects of man often alter a forest's predisposition to damage from both abiotic and biotic effects. For example, soil properties may be altered by heavy machinery. ;Other abiotic factors * Nutrient imbalances: deficiencies, chemicals ( toxic salts, herbicides, air pollutants) * Stemflow which can concentrate dry deposits which via soil acidification can kill surrounding plants. *

Temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

Biotic factors

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

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

Basidiomycota Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

and Fungi imperfecti There is a category listing fungal tree pathogens and diseases in Wikipedia. * Oomycota: Phytophthora *

Bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

* Phytoplasmas *

Viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almo ...

;Insects There is a category listing insect pests of temperate forests in Wikipedia. * Ips (genus) bark beetles * Bark beetle *

Ambrosia beetle Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae), which live in nutritional symbiosis with ambrosia fungi. The beetles excavate tunnels in dead or stressed trees into which they introduc ...

Cerambycidae The longhorn beetles (Cerambycidae), also known as long-horned or longicorns (whose larvae are often referred to as roundheaded borers), are a large family of beetles, with over 35,000 species described. Most species are characterized by anten ...

* Black arches Some of these factors act in concert (all do to a degree). For example, '' Amylostereum areolatum'' is spread by the ''

Sirex noctilio ''Sirex noctilio'', known as the Midnight woodwasp, European woodwasp, European horntail woodwasp, or sirex woodwasp, is a species of horntail, woodwasp, native to Europe, Asia, and northern Africa.New York State Department of Environmental Cons ...

''. The fungus gains access to new trees to live off, and the woodwasp larvae gain food.

Parasitic flowering plants

Many plants can parasitize trees via root to root contact. Many of these parasitic plants originate in the tropical and subtropical climates.

Animals

Nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s especially bark beetles,

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s may browse. Browsing can be prevented with tree shelters. Humans and other mammals predate on trees, and on unsustainable, especially industrial scales, these are demonstrably pathological to the forest. Additionally, poorly planned but conventionally replanted (post-cut) forest plantations are typically monocropped, and highly susceptible to further insect or fungal infection due to low

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

and diminished capacity for community resilience - see the " Wood wide web". Part of forest pathology is forest

entomology Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology that focuses on insects. Those who study entomology are known as entomologists. In ...

. Forest entomology includes the study of all insects and

arthropods Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

, such as mites, centipedes and millipedes, which live in and interact in forest ecosystems. Forest entomology also includes the management of insect pests that cause the degrading, defoliation, crown die-back or death of trees. Thus the scope is wide and includes: * Documentation of all insect species and related arthropods in natural and man-made forests, and the study and ecology of those species. * Description and assessment of damage to tree structures (parts of a tree), to forest stands, landscape effects and to wood products, timber in service and other

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

. * Eradication of recently introduced pests, or long-term management of established exotics and indigenous pests, to minimise losses in wood quality and wood production, and to reduce tree mortality. * Assessments of forest operations, or of management impacts, on the invertebrate fauna, and the alleviation of any adverse effects on these invertebrates.Christian Stauffer, Lecture on Forest Protection 2013, Institute of Forest Entomology, Forest Pathology and Forest Protection, Department of Forest and Soil Sciences, University of Natural Resources and Applied Life Sciences, Vienna, Hasenauerstraße 38, A-1190 Vienna.

Hazard trees

The likelihood of property damage or personal injury due to tree failure. Hazard includes not only the tree's condition, but the potential target as well. Rating systems, procedures and guidelines have been developed for decision making but knowledge, judgement, and experience are an important part to the process.

Pathogens that affect trees

There is a category listing tree diseases in Wikipedia. * '' Armillaria'', which causes white rot root disease * '' Cenangium'' * '' Hymenoscyphus fraxineus'', which causes Ash Dieback * '' Heterobasidion annosum'', which causes Annosum or red root rot, the economically most significant pathogen in the Northern hemisphere. *

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 ...

* '' Rickettsia'', which possibly causes citrus greening disease * '' Spiroplasma'' * Dutch elm disease * Ink disease * Emerald ash borer * Olive tree pathology * Witch's broom * White Pine Blister Rust * '' Phytophthora cinnamomi'', which causes root rot * '' Phytophthora ramorum'', which causes sudden oak death * Polypore or bracket fungus * Tinder conk

Signs and symptoms

Symptoms are a result of a pathogen: *

Blight Blight is a specific symptom affecting plants in response to infection by a pathogenic organism. Description Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. A ...

* Burl * Canker * Chlorosis * Drunken trees * Forest dieback *

Gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or war ...

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 ...

* Leaf scorch *

Root rot Root rot is a condition in which anoxic conditions in the soil or potting media around the roots of a plant cause them to rot. This occurs due to excessive standing water around the roots.-Hydroponics Root Rot: What is It, How To Treat It, How ...

* Virescence *

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 ...

Signs are the visible presence of a part of a pathogen: * Ascus is a part of an

ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

fungus. * Conk (fungi) is the fruiting body of a bracket fungus. *

Hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

are collectively called a

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 ...

Mycelial cord Mycelial cords are linear aggregations of parallel-oriented hyphae. The mature cords are composed of wide, empty vessel hyphae surrounded by narrower sheathing hyphae. Cords may look similar to plant roots, and also frequently have similar functi ...

or rhizomorphs

Pathology detection

This can be done by machines or by dogs smelling the trees, similar to the methods used to find truffles. It can also be done by monitoring and identification can happen via tree clinics, experts such as

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 ...

s or even non-experts through citizen science. It is important to consider the disease triangle when evaluating pathologies. Demonstration of suspected active agents can be done by confirmation of

Koch's postulates Koch's postulates ( ) are four criteria designed to establish a causality, causal relationship between a microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884, based on earlier concepts described by ...

Sources

References

External links

Forest & Shade Tree Pathology

Forest pathology team at INRA Nancy, France

Hazard Trees
{{Authority control Tree diseases