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Forest Invasivesbreadcrumb separatorResourcesbreadcrumb separatorTerms and Definitions

Terms and Definitions

Artificial Spread - human influenced movement of an invasive species from one area to another. Some examples of artificial spread include: the movement of firewood, shipping crates, topsoil, or nursery stock containing invasive species.


Biological control - a control method where a living organism is used to reduce or eliminate the population of an invasive species. The organism used as the biological control may either consume the invasive pest or cause it to become diseased.


Cambium Layer - the layer of wood directly beneath the bark. This layer contains the xylem and phloem tissues; essential for water and nutrient transport within the tree. Many wood-boring insects girdle host trees by damaging the cambium.


Canker - a canker is an isolated dead area on a tree’s bark, stem, branches, or twigs, which can slowly grow and disfigure that part of the tree. Cankers can be caused by fungi, bacteria, viruses, or by physical damage to the tree.


Control - efforts put in place to lessen the effects of an invasive species once it has been introduced. Goals could include complete eradication of the pest, reduction of the density of the pest in an infested area, or reduction of a pest’s spread.


Chemical control - a control method that involves the application of pesticides, herbicides, fungicides, or insecticides to reduce or eliminate the population of an invasive species.


Crown Dieback - this occurs when the crown of a tree starts to lose its foliage and branch tips die. This could be caused by a disease, insect infestation, or if the tree suffers stress, such as from a lack of water or nutrients. It is often measured by the percent of the crown that is dead.


Detection - identifying an invasive species once it has arrived. We need to know that an invasive has arrived so that we can respond quickly to control the spread.


Distribution - the geographic spread of an invasive species on a landscape; the collection of regions where an invasive species has been detected.


Ecological Impacts - the effect that an invasive species introduction has on ecological or environmental factors, such as altered ecosystem services and reduced wildlife habitat.


Economic Impacts - the effect that an invasive species introduction has on economic factors, such as industry losses, management and control costs, and unemployment.  


Epicormic Branches - shoots or branches that sprout from dormant buds on the tree stem or branches, often as a response to tree injury or stress. Excessive epicormic branching can reduce the quality of the wood or cause knottiness in the tree stem.


Eradicate - completely removing all individuals of an invasive species from a geographic area; the best outcome in invasive species management.


Established - species that is surviving and reproducing naturally in an environment. Once an invasive species becomes established, it can spread throughout a landscape.


Exotic Species - a species that is introduced into an ecosystem outside of its native range.


Girdling - the removal of bark around the entire circumference of a branch or tree trunk. Girdling of a branch can cause the branch to die, while girdling of a tree trunk will cause the tree to eventually die.


Host Resistance - a tree that is tolerant to invasive species attacks by inherent or evolved morphological or physiological traits.


Instar - the life phase between two periods of molting in the development of an insect.


Introduction - the arrival of an invasive species to a new environment. Invasive species introductions can occur through natural dispersal, human influence, or other vectors.


Invasive Species - a species that expands out from its native range, and has the potential to disrupt the local balance of the ecosystem and have negative impacts on the ecology, the economy, or society.


Larvae - the juvenile form of a species before metamorphosis (change in form) into the adult form.


Manage - to adapt to the presence of an invasive species; actions to reduce the impacts and long term costs to Canadians once an invasive species has become established.


Manual control - actions such as hand-pulling, digging, flooding, mulching, or manual removal of nests, eggs, or other lifestages of the pest. As this type of control involves a lot of physical labour, it is most effective for small pest infestations and where chemical, biological, or mechanical efforts cannot be used. http://dnr.wi.gov/topic/invasives/control.html


Mast tree - a tree that provides a food source for wildlife by producing fruit, nuts, or seeds.


Mechanical and silvicultural control - can include hoeing, cutting, girdling, tilling, or mowing http://dnr.wi.gov/topic/invasives/control.html.  Trees infested with forest pests can be cut down and their wood can be burned and buried in hopes to slow the spread of an invasive forest pest. Whole logs from trees that have been cut down should not be removed from the area and residues should be destroyed. http://www.exoticpests.gc.ca/control-details/insect/1


Molting - when a species sheds or casts off part of its body during transformation. This can involve shedding the outer layer of its body or losing its wings.


Native Species - a species that has co-evolved with other species in the area and which has long adapted itself within the ecosystem through thousands of years of competition for resources. Native species are a part of the local balance of an ecosystem.


Natural Spread - non-human influenced spread of invasive species; biological dispersal. Some examples of natural spread include: insects flying to new locations, fungal spores transferred by forest animals or wind.


Nymph - the immature form of some insects, which undergo gradual change before reaching the adult phase.


Oviposit - the process of laying eggs.


Parasitoid - an insect used as a biological control agent. Parasitoids have an immature life stage that develops within or on another insect host and ultimately kills the host. Parasitoids slowly kill their hosts by paralyzing them, feeding on their tissues, or laying eggs inside them.


Pathogen - a disease-causing organism, such as bacteria, viruses, or fungi.


Pathway - route of invasive species spread and introduction; facilitated by vectors. Since invasive species are frequently introduced into urban areas, common pathways align with human trade routes and infrastructure.

Physical control - involves putting up barriers to prevent an established invasive species from moving into a new area. http://www.ontario.ca/environment-and-energy/how-you-can-combat-invasive-species


Predator - a species that kills and/or eats another species - its prey.


Prevention - stopping the arrival of an invasive species; the most effective way to manage it.


Pupation - the life stage of some insects during which transformation from one form to another occurs.


Risk Analysis - estimating the impacts of an invasive species by conducting a risk assessment, and analyzing the management options to mitigate the impacts.


Risk Assessment - determining the potential for an invasive species introduction (depending on the biology and pathways of the pest), and quantifying the magnitude of the economic, social, and ecological impacts resulting from the introduction.


Sapwood - the part of living wood where the sap flows; between the cambium and the pith.


Social Impacts - the effect that an invasive species introduction has on society, such as aesthetic value, recreation and tourism, human health, cultural and spiritual values.


Vector - method of spread of an invasive species from one ecosystem to another; the means of transport along a pathway.


Xylem - A portion of the cambium layer of a tree (between the bark and the sapwood); responsible for carrying water and nutrients from the roots of a tree up to its leaves. Many wood-boring insects girdle host trees by damaging this area.