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Annex 1
Definitions and explanations related to tree health




Abiotic factors Non-living factors such as wind, water, temperature, or soil type or texture (FAO)  
Biotic factors Living organisms influencing the environment (opposite of abiotic factors) (IPMRC) Pest organisms that infest trees
Blight A disease characterized by widespread and rapid killing of plant parts (i.e. leaves, flowers, stems) (FAO)  
Canker Dead, discoloured, often sunken area on a plant (FAO)  
Condition   General state of well-being; see also “tree condition”
Damage The adverse effect on plants or crops due to biotic or abiotic agents, resulting in a reduction of yield and/or quality (IPMRC) An injury to a tree, commonly used to describe the effect of insect feeding, but interprete d more generally here
Decline An interaction of interchangeable, specifically ordered abiotic and biotic factors to produce a gradual general deterioration, often ending in death of trees (IUFRO)

A loss in tree vigour; a gradual and general deterioration in appearance leading to complete death


Identification of the nature and cause of an illness, ailment of disease on the basis of its signs, symptoms, etiology, pathogenesis, physiopathology, morphopathology etc.; also the decision reached (FAO/IPPC)

The process of finding out the cause of a tree health problem - not only disease


Progressive death of shoots, leaves or roots, beginning at the tips (FAO)



A condition caused by living organisms or environmental changes that impairs the normal functions of a living organism (FAO)

A harmful deviation of normal plant processes caused by infection with a pathogen


Any harmful deviation from normal plant physiological processes due to abiotic factors (IPMRC)

General description of problems caused by non -infectious agents


A non-parasitic plant that is attached to another plant for mechanical support only; examples include orchids, lichens and mosses (IPMRC)



The state of well-being; physiological and biochemical processes are undisturbed

See “tree health”


Living organisms that serve as food sources for parasites and parasitoids (FAO)

The tree that harbours a pest organism

Ill health


The adverse effect of pests and other factors on the normal appearance of a tree


The introduction or entry of a parasite or pathogenic micro-organism into a susceptible host, resulting in the presence of that organism within the body of the host, whether or not this causes detectable pathologic effects (or an overt disease) (IPMRC)

A plant that is infected and shows symptoms is said to be diseased


A troublesome invasion of insect pests within a particular area (FAO)

Used more generally to refer to invasion of pest organisms





Damage of a plant by an animal, physical or chemical agent which impairs plant growth, function and/or appearance but does not necessarily result in loss yield and/or quality (IPMRC)

“Damage” is more commonly used when describing such events in trees


Death of tissue, usually accompanied by black or brown darkening (FAO)



Microscopic cylindrical worms, parasitic on plants or animals or free-living in water (FAO)



An organism that lives on or in a larger organism, feeding upon it (FAO/IPPC)

Parasites do not infect their host and thus do not cause disease; however, plant nematodes are referred to as parasites and pathogens


Micro-organism causing disease (FAO/IPPC)

Includes fungi, bacteria, viruses and phytoplasmas but excludes insects, weeds and other animal pests, e.g. mammals


The study of disease (FAO)



Any species, strain or biotype of plant, animal or pathogenic agent injurious to plants or plant products (FAO/IPPC)

A primary pest is one that is the leading cause of a problem; a secondary pest contributes to symptoms and damage but is not the principal agent


Organisms (usually fungus) living on dead or decaying tissue (IPMRC)

Saprobe is the preferred term. Note that fungi are not plants and are distinct organisms


Evidence of disease as indicated by the presence of the disease -producing organisms or of any of their parts or products e.g. bacterial ooze or fungus structures (IPMRC)

The use of this term in the narrow sense has been avoided in the guide



A state manifested by a syndrome or bodily changes caused by some force, condition or circumstance, e.g. constraints upon plant growth or survival caused by a harsh environment


The apparent changes in an organism as a result of attack, such as by a pathogen or pest (FAO)

Put simply, this is when “something does not look right” Used in a general sense to refer to all visible evidence of ill-health in trees


The totality of effects produced in a host by one disease, whether simultaneously or successively and whether detectable to the unaided eye or not (IPMRC)


Tree condition


The state of health of a tree

Tree health (individual trees)


''Health of the tree” is the preferred phrase when referring to the state of well-being or normal growth and development individual trees

Tree health(general topic)



The study and consideration of factors that influence the state of well-being and the effects th ese have on the tree


Literally “a carrier”. An animal carrying a microorganism pathogenic for members of another species; the vector may or may not be essential for the completion of the life cycle of the pathogenic micro-organism (IPMRC)


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