Table 1 Description of the Btk spray application scenarios that were compared in this study, and efforts invested in each one over 11 years of implementation, as expressed by the overall number of Btk spray applications conducted for each scenario, and cost of Btk interventions depending on the number of years of treatment and aerial applications for the different protection scenarios
Scenario | Description | Rationale behind each scenario | Number of years of treatment | Number of Btk applications | Mean cost (CAD/ha) | Total cost (CAD/ha) |
|---|---|---|---|---|---|---|
1 | No protection | Control (SBW impact when no protection is applied) | 0 | 0 | 0 | 0 |
2 | Very light protection (Btk applied every 3Â years) | It aims to reduce mortality in susceptible hosts. The spruce budworm outbreak could induce certain thinning by killing weak trees, such as those exhibiting a small crown. Such thinning would favor future crop trees, thereby producing an interesting timber volume after the end of the outbreak | 4 | 7 | 23.31 | 279.69 |
3 | Light protection (Btk applied every 2Â years) | The objective of this scenario is to reduce tree mortality and growth losses. This strategy could be allowed to either rotate the areas to be protected or increase the area treated without additional cost | 6 | 11 | 36.46 | 437.55 |
4 | Standard protection (Btk applied 1 year after moderate to severe defoliation to keep defoliation ≤ 50%) | Standard strategy used in Quebec. It aims to protect at least 50% of current-year foliage to avoid tree mortality | 11 | 20 | 65.97 | 791.59 |
5 | Intensive protection (up to three Btk applications per year) | The purpose of this strategy is to keep SBW defoliation at 20% or less to reduce growth losses and tree mortality to a minimum | 12 | 29 | 89.15 | 1069.83 |