Common or important forest health terminology that may have occurred in this chapter or that is useful to be aware of. For a full glossary of Forest Health terminology (PesTerms) see Doliner and Borden (1984).
Basal Resinosis (Pitching): Large exudations of pitch at the base of the stem at or below the root collar, often associated with Armillaria root disease or Warren's root collar weevil. See also Resinosis.
Broom/ Brooming: In woody plants, an abnormal shortening of internodes (the region of stem between any two nodes, places where leaves attach) and proliferation of weak shoots, forming a dense brush-like mass (also called a witches' broom). Commonly induced by dwarf mistletoes, rust fungi, or other organisms, but sometimes a response to abiotic stresses. Mistletoe brooms are evergreen, while needles of brooms induced by rusts generally last only one year.
Canker: A localized, well-delineated area of diseased tissue in bark and cambium of main root, stem, or branch, often with an overgrowth of surrounding tissues as a result of reaction of the host plant to infection.
Chlorosis: Yellowing of normally green tissue, due to destruction or reduced production of chlorophyll, often a symptom of some metabolic deficiency, disease, feeding by sucking insects, root or stem girdling, or extremely reduced light. A distinction is sometimes drawn between lack of colour due to growth under insufficient light (etiolation) and that due to some other cause (chlorosis).
Crook: A defect in trees or logs, consisting of an abrupt bend, that can result from insect-induced topkill and recovery by a lateral branch. A minor crook is called a Crease. See also Fork, Shepherd's Crook, and Staghead.
Damage: The physical and ecological effects of a forest health factor on tree or forest growth, structure, productivity, and/or use.
Decay: The decomposition of wood caused by fungi, resulting in softening, progressive loss of strength and weight, and often changes in texture and color. See also Laminar Decay and Rot.
Dieback: The gradual and progressive dying, starting at the tips, of shoots, twigs, tops, branches or roots.
Duff: The organic litter layer of the forest floor comprised of organic debris such as leaf litter, bark fragments, twigs, etc. in varying states of decomposition.
Flagging: Conspicuous, red or chlorotic branch in a green crown.
Fork: A major defect resulting when two laterals assume dominance, possibly caused by loss of a leader or apical shoot due to terminal weevils. See also Crook, Shepherd's Crook, and Staghead.
Frass: Solid insect excrement of insects, particularly larvae; that of wood-eating insects such as bark beetles can be called boring dust.
Frequency: the number of repetitions of a periodic process (e.g. defoliator outbreak) in a period of time (e.g., in a 25-year period). A relatively high frequency would be an outbreak every decade.
Fungal Anatomical Structures :
Conk: The shelf-like or flat spore-producing structure of some wood decay fungi, particularly heart rot fungi; forms on the external surface of its host; seen on tree trunks, branches or stumps.
Ectotrophic Mycelium: A mass of white or gray mycelium found on the outside surface of roots; the mycelium may be covered by a dark brown crust if it has been exposed to the air. Ectotrophic mycelium facilitates the initial spread of Phellinus weirii from root to root. See also Mycelium.
Fruiting Body: Fungal structures that contain or bear spores, such as mushrooms and Conks.
Hypha (Plural Hyphae): A microscopic, fine, thread-like, often branched structure formed of fungal cells.
Mycelial Fans: Fan-shaped mass of hyphae, formed between bark layers or between bark and wood of trees. Often found near the base of trees infected with Armillaria root rot.
Mycelial Sheet: A felt of hyphae, in other than a fan-shaped pattern, formed in cracks in decayed wood, or between bark layers or between bark and wood of trees.
Mycelium: A mass of vegetative, interwoven hyphae, usually considered as distinct from the fruiting body. See also Ectotrophic Mycelium .
Rhizomorph: A rootlike strand composed of hyphae, often much branched, occurring in certain fungi, e.g. Armillaria.
Gallery: A passage, burrow, tunnel or mine excavated by an insect (especially by bark beetles) in plant tissues for feeding, oviposition, or shelter. Bark beetle galleries are constructed in the inner bark and often may etch the surface of the wood. Their general pattern is characteristic for particular genera and even for certain species.
Galls/ Galling: A localized proliferation of greatly modified plant tissue, induced by another organism such as an insect or disease fungus, that results in a pronounced permanent swelling, lump, or abnormal outgrowth of malformed bark or woody material. Commonly has a characteristic shape, often spherical, unlike any organ of the normal plant.
Girdling: The destruction of the conducting bark tissues (phloem) all the way around a trunk, stem, branch or root, preventing the movement of photosynthetic products and causing the affected plant part to die. When the trunk is girdled, nutrient depletion may cause the roots to die, cutting off the water supply to the crown, thus killing the top as well. Many deciduous trees once girdled can repair the damage and survive. Girdling may be caused by bark beetles, weevils, rodent gnawing, or fungal infections.
Gouting: Excessive swelling of a branch or shoot, often accompanied by misshapen needles and buds; frequently caused by balsam woolly adelgid on true firs.
Incidence: The proportion or percentage or frequency of occurrences of a given phenomenon, such as a disease or insect infestation, in a defined sampling unit (normally a plot or a stand). To avoid confusion when using incidence, always indicate the sampling entity and sampling unit.
Laminar Decay: Decayed wood separating readily along growth rings (= delamination), characteristic of infection by Phellinus weirii .
Lion's tail: The isolated tuft of current needles remaining on branches or branchlets after all the other needles have been cast as the result of a severe foliage disease.
Necrosis: The death or disintegration of cells or tissues while they are still part of a living organism; in plants usually resulting in a darkening of the affected tissue.
Parasite: An organism that lives part or all of its life cycle in (endoparasite) or on (ectoparasite) a different organism, the host, and from which it derives part or all of its sustainance. See also Parasitoid.
Parasitoid: A parasite, typically an endoparasitic fly larva or wasp larva, that ultimately kills its host, often by consuming most or all of its internal tissues. See also Parasite.
Pathogen: Organisms (usually very small or microscopic) such as bacteria, fungi, protozoa, helminths, viruses, or viroids, that cause or induce disease in their host.
Pitch Tube: A mass of resin and often frass or boring dust at the point of entry of an insect (often a bark beetle) tunnel into bark, cones etc. of various conifers, as a result of the severing of resin ducts by the boring activity of the insect.
Primary Bark Beetles: A bark beetle that is the first to arrive at, utilize, complete development in, and/or kill an apparently healthy, living tree. See also Secondary Bark Beetles.
Resinosis: Flow of resin or pitch in a conifer, in response to infection, wounding or insect (often bark beetle) attack. See also Basal Resinosis.
Root Collar: The part of a tree where the main roots join the trunk, usually at or near ground level.
Rot: A state of (usually advanced and obvious) decay caused by fungi. The word rot also refers to or is part of the name of a disease characterized by this symptom. See also Decay.
Saprophyte: An organism that commonly feeds on dead organic material, usually by decomposing and absorbing it, and assisting in its decay. Saphrophytes, in certain circumstances, may attack living hosts (e.g., those weakened by primary pathogens or stress) and become pathogens.
Secondary bark beetles: A bark beetle that attacks trees that are already weakened, dying or dead as a result of a primary insect (often a primary bark beetle) or pathogen.
Shepherd's Crook: A leader or branch with a down-curved tip in the shape of a shepherd's crook, characteristic of attack by certain insects (especially terminal weevils on spruces) or pathogens (for example, Fusarium root rot in Fd seedlings). See also Crook, Fork, and Staghead.
Sign: Objective evidence, such as the visible portion of a pathogen, or its products, seen on or in the host. Compare with Symptom.
Staghead: three or more laterals assuming dominance; a major defect often resulting from terminal weevil attack. See also Crook, Fork, and Shepherd's Crook.
Symptom : A phenomena, or circumstance observed or detected in the host that is associated with, or a known reaction to, disease, infection, injury, or attack. Compare with Sign.