ARCHIVED - Pest Risk Assessment Summary
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The Brown Spruce Longhorn Beetle (BSLB) is currently found within 6 counties of central Nova Scotia. The Canadian Food Inspection Agency (CFIA) has conducted a Pest Risk Assessment (PRA) to better understand the dynamics of the BSLB in Nova Scotia.
The PRA follows a format and terminology laid out by the International Plant Protection Convention of the Food and Agriculture Organization of the United Nations. A PRA provides an assessment of the plant pest risk based on scientific literature, scientific data and an analysis of potential pathways of introduction. It also rates the risk in a number of categories. The PRA also recommends potential ways of reducing the risk that may be used to prevent introduction/spread of the pest in Canada.
It should be noted that a PRA is a living document, and information on the ecological, economic and scientific significance may be revised as it becomes available and new information is gathered. The gathering of comprehensive knowledge of a pest in a new environment takes years of intensive research, in which time an invasive forest insect such as the BSLB may cause extensive long-term damage to the ecosystem and the economy that relies upon it. The PRA produced by the CFIA has incorporated the most current information possible supplied by national and international experts.
The complete PRA provides specific information pertinent to this pest. The risk associated with the BSLB has been characterized and estimated. Major points determining the risk posed by this pest are summarized in the following chart.
|Pest Organism(s)||Status in PRA Area||Likelihood of Introduction||Potential Introduction Impacts||Overall Risk Rating||Level of Uncertainty|
|Brown Spruce Longhorn Beetle (Tetropium fuscum)||Present||Medium||Medium||Medium||Medium|
The overall risk rating for the BSLB, using the current rating scheme, is medium.
Biology of the BSLB in its Native and New Habitat
In its native range in Europe and Asia, the principal hosts of the BSLB are conifers, in particular Norway spruce. In this environment this insect is not considered to be a pest of economic importance as it attacks trees that are already stressed by other factors. Considering this, little research has been conducted on this species in those areas where it occurs.
In central Nova Scotia, the BSLB is attacking live, apparently healthy spruce trees in substantial numbers, which indicates that it is acting differently with new hosts in its new environment. In the Point Pleasant Park, Halifax infestation, it appeared that healthy spruce trees died three years after the initial attack. Beetles appear to re-infest the same host until it dies. This suggests that the BSLB will show much more potential for damage in Canada than has been demonstrated in its native habitat.
The geographic range of the species in Europe and Asia indicates that the BSLB is cold hardy and its Canadian distribution will not be limited by the winter temperatures which characterize the general distribution of spruce in North America. No clear and direct evidence of flight range of the BSLB has been reported in its native range.
Yield Losses and Reduced Marketability Due to Damage by BSLB
The BSLB could be of particular concern in healthy mature spruce trees, which are conducive to the build up of insect populations. Controlling the BSLB over wide areas could be difficult and expensive. In general, chemical treatment, if it became possible and available, would be costly and labour intensive. Mechanical control would also be costly and labour intensive.
Red spruce is an extremely valuable resource for pulp and lumber production. The characteristics of the tree make it very useful in the Maritime forest. It can tolerate the climate and the soils very well, and is tolerant of shade for decades if necessary. This makes it a major contributor to the Maritime forest industry, and any reduction in its availability would be a very important loss. Across Canada the establishment of the BSLB could cause widespread tree mortality that would be very disruptive to the forest-based industries, which are the largest industries in the Canadian economy. In addition, protected old-growth and urban forests in Canada would all be at risk should the BSLB become widespread.
Impacts of the BSLB on Non-Commercial Forest Values
The BSLB would not directly prevent the regeneration of all spruce species in Canada as it prefers hosts over 10 cm in diameter. However the BSLB might significantly reduce the frequency of mature red spruce stands, or even eliminate them completely as this species does not begin to produce seeds until about 75 years of age or greater. Red spruce is the provincial tree of Nova Scotia, and is therefore an acknowledged symbol, and key component, of the forests of this area of Canada.
The loss of mature red and other spruce stands would affect the biodiversity of all of Canadian forests. Numerous indigenous species of plants, animals and microorganisms would be deprived of their essential critical habitat, and so would decline in abundance in the wake of beetle-caused stand-level mortality.
Recreation and aesthetic values could be severely affected in urban or park-like settings by the BSLB. The death and removal of large specimen trees in these settings has an impact on the users which far outweighs the commercial value of such trees.
Cultural Practices and Control Measures
The most effective means of controlling the BSLB is to conduct sanitary harvesting (removing and burning or chipping/grinding the affected host tree) in order to reduce brood material. No chemical pesticide is currently registered to control the BSLB in Canada. Extensive and long-term research would be required to determine the effectiveness of any proposed chemical agent, and to establish application methodology, appropriate dosages, etc., against the BSLB. Various parasites and predators occur in Canada that can reduce larval populations of related boring beetles of the BSLB. These parasites could behave more aggressively in attacking the BSLB in its new Canadian environment than in its native habitat, but no observations on interactions with native parasites have yet been made in Canada.
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