The brown spruce longhorn beetle (BSLB) is an invasive forest insect from Europe that infests spruce trees. It has been established in Nova Scotia since 1990. Below are answers to frequently asked questions about BSLB.
Where is BSLB in Canada?
To date, BSLB has not been found established in any area of North America outside of Nova Scotia. In 2011, a single specimen of BSLB was captured in a Canadian Food Inspection Agency pheromone-baited survey trap in Kouchibouquac Park in New Brunswick. The long distance from the known area of established BSLB populations in Nova Scotia suggests the BSLB arrived at the park through artificial movement of infested material, likely firewood. Additional surveys will be conducted in 2011 and 2012 to determine whether this specimen represents an established BSLB population in the park or was intercepted from infested material moved to the site.
Where did BSLB come from?
BSLB is native to northern and central Europe and western Siberia. In 1998, Natural Resources Canada–Canadian Forest Service researchers discovered many dead and dying trees in Point Pleasant Park in Halifax, Nova Scotia. It was then determined that the BSLB had been established in Nova Scotia since 1990, and likely arrived in wood packaging in container ships from the port adjacent to the park. Since 2000, BSLB has been under regulatory control by the Canadian Food Inspection Agency as a quarantine pest, and the agency has implemented a BSLB risk mitigation program.
How is BSLB threatening spruce trees?
BSLB larvae feed on fresh phloem tissue (live bark) that transports food from the tree’s foliage to the roots. Sufficient larval tunnels girdle the tree, cutting off the flow of nutrients to the roots and weakening the tree. Once BSLB infests a tree, it will re-infest it year after year until the tree dies, in one to five years. Spruce trees are found across Canada; BSLB has the potential to spread throughout the range of red, white, black and other species of spruce in North America.
What is the impact of BSLB on forests?
The Canadian Forest Service (CFS) is researching the impact of BSLB on forests by establishing long-term plots to monitor changes in tree mortality over time; these plots are in areas outside the current containment zone (where BSLB populations are of lower density) and inside the containment zone (where BSLB populations are of higher density). This provides a series of snapshots over time to monitor the insects’ impact on spruce forests.
Researchers have found that while recent mortality is very patchy, tree mortality in the plots can range from 0% to as high as 78%. Studies by CFS-Atlantic researchers indicate that BSLB has infested and killed a mean of 30% of spruce basal area from 2008 to 2010 in sites near Halifax. Mature spruce forests in Canada, especially those under stress from defoliator outbreaks or drought, are at risk of BSLB infestation and accelerated mortality.
Does BSLB attack healthy trees?
In Europe, BSLB is a secondary pest that attacks trees that are weakened and/or stressed trees by root rots or other factors.
In Nova Scotia, BSLB is more aggressive, attacking apparently healthy spruce as well as dying and recently fallen spruce trees. Recent research has confirmed that while BSLB can infest healthy spruce, it prefers spruces that are stressed. In the absence of BSLB, red spruce under stress can survive many years of reduced growth rates (caused by factors such as drought, wind damage and defoliation during spruce budworm outbreaks) and bounce back when conditions improve. However, once a stressed spruce is infested by BSLB, it will die in one to five years.
How does BSLB spread?
There are two ways that the beetle can spread: naturally and through human-assisted or artificial movement.
The Canadian Forest Service researchers examined the natural spread of BSLB (i.e., how far the beetle can move on its own) by doing lab experiments (called “flight mills”), attaching radar tracking devices to the insects, and conducting mark-release-recapture experiments in infested forest areas. In the lab, BSLB tend to make many short flights or not fly at all: some have flown more than 10 kilometres in 24 hours, and the average lifetime distance flown is about 2 kilometres. In the field, flights averaged about 25 metres. Analysis of survey data suggests that the natural rate of spread outward from the edge of the infestation is very slow and that detections of BSLB in “outlier” sites (more than 80 kilometres from Halifax) are likely the result of artificial movement.
Human-assisted or artificial movement occurs when infested wood is moved from place to place. This can occur with logs, wood chips or even firewood brought to campsites. The Canadian Food Inspection Agency has measures in place to restrict the movement of certain articles.
How do I recognize BSLB?
Please visit the Canadian Forest Service’s Trees, insects and diseases of Canada's forests website for information on recognizing BSLB and signs and symptoms of infestation.
Note: It is difficult to visually identify BSLB without the aid of a microscope, as the insect looks quite similar to the native bark beetle (Tetropium cinnamopterum). If you suspect a BSLB infestation, please contact the Canadian Food Inspection Agency (CFIA) (in Nova Scotia, call 1-877-868-0622 or 902-426-4667; outside of Nova Scotia, visit the Canadian Food Inspection Agency’s website to find out how to contact your local CFIA office).
How is BSLB detected in a forest?
The Canadian Forest Service (CFS), the Canadian Food Inspection Agency and the Nova Scotia Department of Natural Resources partner each year to place traps to monitor and detect BSLB populations.
CFS has created a BSLB risk analysis model, which enables forest managers to predict areas that are more vulnerable to BSLB infestation or more likely to have existing populations. Researchers input forest types, locations where BSLB has been detected, places where wood is moved (e.g., lumber mills and campgrounds), the location of ports, and other values, with the aim of identifying areas where BSLB is more likely to be found. The model has greatly improved researchers’ ability to know where to place pheromone traps in Nova Scotia.
The traps are baited with a BSLB-specific pheromone called “fuscumol,” as well as two lures that emit spruce tree odours. The BSLB sex pheromone was identified and synthesized by CFS researchers and has significantly increased the ability to detect the BSLB in the field. Expanded surveys in 2007 and 2008 with the improved trap lure detected BSLB at 26 new locations beyond the containment zone boundary established in May 2007.
How are BSLB populations managed?
There are several options being explored by the Canadian Forest Service scientists: parasites, predators and pheromone-based controls for mass trapping and mating disruption, as well as best management practices and risk mitigation.
Parasites and predators: Two native wasp species attack an average of 10–20% of the BSLB population. Woodpeckers and native checkered beetles have also been found to prey on BSLB. In addition, researchers have found that when BSLB is exposed to natural enemies, BSLB survival is greater in healthy trees than in stressed or felled trees.
Pheromone-based controls for mass trapping and mating disruption: The pheromone “fuscumol” has been in evaluation since 2008 as a tool for mass trapping (directly capturing female beetles before they lay eggs on trees) and mating disruption (pheromone “scent” confuses the insects, preventing them from finding a mate).
Mass trapping experiments done in 2008 and 2009 found that when traps baited with fuscumol and spruce odours were placed in high densities (100 traps per hectare), BSLB infestation in bait logs was significantly reduced. Researchers are currently testing to see whether BSLB populations are suppressed through mass trapping using a lower, less costly density of 25 traps per hectare.
Mating disruption trials conducted in 2008–2010 indicated that broadcast application of fuscumol on Hercon Bio-flakes significantly reduced the percentage of female BSLB that successfully mated and reduced BSLB infestation in spruce.
Best management practices: A pamphlet on best management for BSLB management on Nova Scotia woodlots has been produced through a partnership of the Canadian Forest Service, the Canadian Food Inspection Agency, the Nova Scotia Department of Natural Resources and the Nova Scotia Association of Woodlot Owners.
Risk mitigation: The Canadian Food Inspection Agency’s Brown Spruce Longhorn Beetle Risk Mitigation Program includes
How do we know that the observed tree mortality has been caused by BSLB and not by the native spruce bark beetle?
Researchers have examined and compared the damage caused by BSLB and the native spruce bark beetle. They found that trees affected by these two insects have different infestation symptoms.
Spruce bark beetles bore through the bark and lay eggs in the phloem layer of the tree. Spruce trees respond to this attack by producing large amounts of pitch or tree resin to push the insect out; this forms pitch tubes on the outside of the tree—round, popcorn-shaped forms that protrude 1–2 centimetres from the bark surface.
With BSLB, the females lay eggs under bark scales and in crevices. When larvae hatch, they bore into the bark to the phloem layer. The resin flows out of these bore holes and down the tree. The greater the attack rate, the greater the amount of pitch flow down the stem of the tree.
By observing whether trees have pitch tubes or resin flow, researchers are able to determine which trees died from spruce bark beetle infestation and which died from BSLB infestation.
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