The Upper Bowron Spruce Beetle Outbreak: A Case History  
  By Russ Cozens M.F. (UBC '84)  
The upper Bowron River valley is located 80 kilometers southeast of Prince George, British Columbia. The Bowron River flows from Bowron Lake to its confluence with the Fraser River, some 110 kilometers to the north. Bowron Lake is part of the very popular Bowron lakes canoe route. The Bowron River has significant salmon spawning values.   Interior spruce forest
    Fig. 1. Interior spruce forest
Strong winds caused widespread blowdown in the upper Bowron River valley and, to a lesser extent, in adjacent valleys, in October 1975. Steady wind speeds reported at 75 kilometers per hour (kph), with microbursts producing winds approaching 150 kph, uprooted and broke-off trees throughout the area. Patches of up to 250 hectares were totally flattened by the winds. As well, the windstorm toppled the more-or-less uniformly distributed 3 – 5 stems per hectare over a widespread area.   Patch blow down in spruce forest
    Fig. 2. Patch blow down in spruce forest
Wind – a natural disturbance factor

Mature to overmature interior spruce (Picea glauca x engelmanni) and interior spruce-balsam (Abies lasiocarpa) mixes, with volumes approaching 305 m 3 per hectare, typified the forests of the upper Bowron. These forests continue to provide a high quality raw material to the processing facilities that are located mainly in Prince George.

All of the land in the upper Bowron river drainage is owned by the Province of British Columbia, and is managed for the people of the province in a manner that is consistent with the Ministry of Forests Act, the Forest Act and, since July 1995, the Forest Practices Code of British Columbia Act. Forest management operations are conducted by the holders of various agreements with the Crown. In the late 1970's, the management agreement was a timber sale harvesting licence (TSHL). These have now been replaced with forest licences which are similar in nature to TSHL's but place increased management responsibility upon the licensee, in return for increased security of tenure.

The TSHL holders in the upper Bowron were confident that they could remove the patch blowdown before it deteriorated. However, much of the area was inaccessible. Access development began almost immediately. Fortunately, road construction was quite straightforward and the only problems encountered were those associated with hauling logs over newly constructed roads.   Road construction
    Fig. 3. Road construction
Fading spruce indicating spruce beetle attack   Discoloured spruce trees were noticed by Forest Service staff in mid-April of 1979 when returning from field work on the “last” blowdown block. Subsequent ground inspections showed significant activity of the spruce beetle (Dendroctonus rufipennis Kirby) in the area of the discolored trees. Further examination showed a substantial problem throughout the upper Bowron and a somewhat lesser problem in adjacent drainages. This “discovery” took place 3½ years after the initial blowdown event.
Fig. 4. Fading spruce indicating spruce beetle attack    

Outbreak Characteristics

Population build-up took place in the more-or-less uniformly distributed 3-5 mature spruce trees per hectare that were felled by the windstorm of October 1975. The population did not build in the patch blowdown, for two reasons: (1) most of the patch blowdown had been removed in the 1975/76 – 1978/79 logging seasons; and (2) spruce beetles did not aggressively colonize the patch blowdown material, presumably because of inhospitable host bark temperatures due to prolonged exposure to direct sun. This second point is extremely important in refuting claims that the unharvested patch blowdown in the Bowron Lakes Provincial Park was where spruce beetle populations built to epidemic proportions.

Several warm winters with heavy snowpacks resulted in very low overwintering mortality in the spruce beetle populations. Early springs and warm summers set the conditions for one-year life cycles. Overlapping one and two-year cycles resulted in huge dispersion flights and dramatic expansion and intensification of the infestation. The general boundaries of the infestation encompassed about 175,000 hectares, not all of which was attacked by spruce beetle.

Decision Making Challenges and Processes

Staff training and awareness in pest management was minimal prior to 1980. Understandably, it became a high priority item to enable both the Forest Service and the forest industry to meet the “challenge” with which we were presented.

Detection of insect activity essentially had been dependent upon the Canadian Forestry Service's Forest Insect and Disease Survey overview surveys and “random” observations by Forest Service and industry personnel. Early detection, infestation quantification and population monitoring became a very high priority so that both the Forest Service and the forest industry could determine the ever-changing extent of our “challenge”.

The overall goal in addressing the spruce beetle outbreak in the upper Bowron River area was that of limiting the expansion of the infestation by harvesting green-attacked timber. Harvesting the green-attacked timber would remove the beetle populations from the area, thus reducing the potential for expansion, and would also maximize the value of the trees at the mills since they were still in good condition (i.e., not “checked”, no sap rot, etc.).   Harvesting the green attack
    Fig. 5. Harvesting the green attack


The Bowron was only one of the several “hot spots” in the Prince George Forest Region in the early 1980's. Spruce beetle, mountain pine beetle ( Dendroctonus ponderosae Hopk.) and Douglas-fir beetle ( Dendroctonus pseudotsugae Hopk.) were keeping region and district staff busy in all but two of the nine forest districts in the then Prince George Forest Region. The region included about 32 million hectares of land and occupied about one third of the province of British Columbia. It is presently administered as part of the Northern Interior Forest Region.

Control of the spruce beetle outbreak was to be accomplished through harvesting the green-attack spruce trees. Removal of beetle populations with the attacked trees would limit the outbreak expansion. As well, the timber would be utilized while it was virtually undamaged, thus maintaining its value to the licensees, the secondary manufacturers, and to the people of British Columbia.

The licensees that traditionally operated in the upper Bowron River area realized very early that they were not able to address the problem in an appropriate manner on their own. Thus, it was necessary to relocate licensees from adjacent areas to provide more harvesting “horsepower” and allowable annual cut (AAC). (TSHL's had a specified volume of timber to be harvested each calendar year, which is the AAC. Forest licences also have an AAC). A memorandum of understanding was drawn up with each of the relocated licensees to state clearly the terms of the relocation, including the important provision that they would return to their normal operating area at the completion of the Bowron project.

Planning, referral and approval processes were streamlined to the maximum so that a problem area could be addressed shortly after it was identified. Commonly, attack areas were identified from ground surveys in late summer/early fall, and cutting permits were issued to the licensees by “freeze-up” in November. Harvesting would take place during the winter; site treatment, which generally included broadcast burning, would take place in the late summer or early fall. It became evident very early in the project that full and complete cooperation between the Forest Service and licensees and among the licensees was critical for success. We most certainly did not want “process” to create more problems or compound the ones that we were addressing.

Coordinated harvesting operations removed 15 million m 3 of green attacked timber between 1981 and 1987. This amount of raw material could produce enough lumber to build 900,000 average 1,200 square foot homes! Logging trucks, with radiator caps touching the red flag of the truck in front, carrying 15 million m 3 of logs would stretch for 5,300 miles. The peak of the harvesting activity saw some 700 loads of logs coming from the Bowron every day. One-way transportation patterns were established, and were particularly necessary during the very busy winter logging period. As well, off-highway access was developed into the Prince George mill sites so that truckloads could be larger, thereby reducing the total number of trips required, the cost of each cubic metre of delivered wood, and road congestion.  
Trucking logs out of the wood
Fig. 6. Trucking logs out of the wood
  In mid-1980's figures, about C$870 million of product was removed in the 1981-1987 period. C$27 million was returned to the province in the form of stumpage and direct taxes. At today's (1997) significantly higher stumpage rates, that amount would be close to the C$250 million range.  
Within the 175,000 hectare outbreak area, 48,000 hectares were harvested and an additional 3,300 hectares were burned by wildfire. Clearcut harvesting is the best preparation for these boreal forests and was prescribed throughout the Bowron. Ground-based skidding systems were employed, primarily using rubber-tired skidders.   Extensive clear-cut readily visible from space
    Fig. 7. Extensive clear-cut readily visible from space
Trap log in forest   Trap trees, both conventional and lethal, trap logs and trap decks (commonly used in road construction) were utilized outside of the main outbreak area to prevent smaller areas from expanding. We could ill afford another large scale beetle control/sanitation salvage project at this time.
Fig. 8. Trap log in forest    

Assessment of Program Effectiveness

The assessment of the program effectiveness was quite simple: did the expansion continue? Essentially, we “chased beetles” until the populations were not killing significant numbers of mature spruce trees. The assessment was subjective in nature only, since we couldn't afford to have a control area by which to judge our performance.

A New Forest


The plantations of the upper Bowron River valley are extensive. They can be seen from space! Some 62.5 million trees have been planted on 43,500 hectares. The remaining 650 hectares were planted by 1999. Natural regeneration is expected on 1,200 hectares of lodgepole pine ( Pinus contorta Dougl. var. latifolia ) sites. Safety and environmental concerns precluded about 2,800 hectares from planting.

The plantations are comprised of 70% interior spruce, 28% lodgepole pine and 2% Douglas-fir. Thus far, 13,100 hectares of these plantations have received some form of stand tending.

  Bowron Valley land now covered with plantations
  Fig. 9. Bowron Valley land now covered with plantations


The upper Bowron River windstorm and spruce beetle outbreak provided the Forest Service, licence holder and the public with challenges and opportunities. Access into the area was developed in relatively short order that could be used to facilitate forest management activities including insect and disease detection and control, fire management and control, and harvesting and related activities. The public could extend their pursuit of recreational activities into previously inaccessible areas. Employment opportunities in the logging, milling, manufacturing and support sectors were increased due to the concentration of operations in the upper Bowron.

Techniques for the detection, control and management of spruce beetles, and other bark beetles, were developed and fine-tuned in the upper Bowron and adjacent areas. Many of these techniques have been used in other areas of the Prince George Forest Region and British Columbia with success.

Most important, the upper Bowron spruce beetle outbreak raised the awareness of pest management (=forest health) in both the Forest Service and the forest industry. Media coverage during the project served to bring an awareness of certain forest pest issues to he general public. An industry colleague, responding to claims of “beetle eradication” in a particular area (not in the Prince George Forest Region!), perhaps summed up the pest awareness issue most appropriately:

“The beetles aren't gone; they're just resting.”

Footnote: This experience with the spruce beetle in the Bowron River Valley provided a rich experience which was encapsulated in the Forest Practices Code Bark Beetle Guide Book. You are encouraged to read this Guide Book for additional details.


Russ recently retired from his position as Senior Forester, Evaluation and Assessment, Forest Practices Branch, BC Forest Service, Victoria, BC. He has been very active in Forest Pest Management over the last 20 years. This account is based on Russ's personal experiences in the Prince George Region. The paper was presented to the 1997 Western Forest Insect Work Conference that was held in Prince George.

  Edited by: John A. McLean
Page designed by: Adrian Behennah
Version: August 2004
  Note: The side bars show the underside of spruce bark engraved with beetle galleries.  
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