Comparison of Two Treatment Regimes for Managing Western Balsam Bark Beetle

Abstract

The efficacy of pheromone-baited, standing subalpine fir Abies lasiocarpa (Hook) Nutt. and felled green trap trees was tested in southern British Columbia as potential manage- ment techniques for containing western balsam bark beetle Dryocoetes confusus Swaine populations prior to logging. In the year treatments were deployed, standing trees in close proximity to baited trees had significantly higher levels of current attack than those near felled trap trees or in control blocks. The control blocks had the lowest level of current at- tack. Diameters of attacked trees were significantly greater than unattacked trees in all treatments. Naturally attacked, standing subalpine fir had high levels of occupation (number of nuptial galleries) along the full length of the bole. Baited trees had similar levels of occupancy up to six metres in height. Felled green trees had lower occupancy than the baited or naturally attacked trees. Although baited trees concentrated attack into a discrete area, they did not artificially trigger an outbreak or further population expansion in the year following treatment. Felled trap trees appeared less attractive to western balsam bark beetle than natural, susceptible, standing subalpine fir; they are more difficult to de- ploy and therefore not recommended as a means of containing western balsam bark beetle prior to logging.