Beetle management units (BMUs) are the basis for developing landscape level management strategies to deal with bark beetles. BMUs are intended to identify areas where specific beetle management strategies can be applied. BMU boundaries should coincide with established boundaries of existing management units. Beetle management strategies are broad approaches that have specific objectives. Each strategy has an associated array of applicable tactics or treatments. These treatments are applied to specific infestations or areas within the BMU to achieve the objective of the strategy. BMUs will provide a basis for evaluating damage to timber, impact on other resources, effectiveness of treatment, and resource allocation and monitoring. BMU strategies should be incorporated into all higher-level planning processes such as development plans.
BMUs cannot be considered in isolation as each will have an effect on the beetle
situation of its neighbor. Therefore, the strategy selected for a BMU must be
compatible with those taken in adjacent units and with the overall integrated
resource use plans for the area.
Strategies
There are six strategies that can be used to address bark beetle infestations.
Selection of the relevant strategy is based on the extent and distribution of beetle
infestations in an area. Strategy selection must also consider resource
management objectives and the expected impact of the beetle in adjacent
management areas. The selected strategy will define which treatment
combinations are most appropriate and the intensity and frequency of their
application. A combination of strategies is possible within different sub-units.
The six strategies are:
The strategy chosen should remain in place for as long as the objectives are
being met or until additional resources become available to allow a more
aggressive strategy to be implemented. However, situations change from year to
year and therefore strategies must be reassessed on an annual basis. The most
technically correct strategy may not always be selected since other criteria can
override technical considerations.
Prevention (long-term approach)
Prevention as a strategy is applicable to a large area of uninfested or lightly
infested timber with a moderate to high hazard rating. The prevention strategy
can also be used concurrent with other strategies in infested areas. The intent of
the strategy is to reduce future losses through manipulation of forest cover.
Long-term landscape level management includes plans aimed at age and species
mosaics unfavourable for large outbreaks of bark beetles. This includes planning
for construction of major access routes into moderate and high hazard drainages.
Prevention strategies also indicate that harvesting plans should be based on existing hazard and risk criteria. That is, stands with high hazard and close to beetle population centers (high risk), should be logged or modified on a priority basis. The overall strategy is to remove the susceptible host in an organized manner that will not create extensive and continuous stands of susceptible forest over the next rotation. Allowance should be made in landscape level plans for encouragement of insectivorous birds (e.g., woodpeckers) that aid in maintaining beetle populations at low levels.
Prevention also relates to reducing the susceptibility of a particular stand or to
reducing its attractiveness to the beetles. This could also be considered a “tactic”
to be incorporated into all strategies. The most common method is to selectively
log a stand to a pre-determined spacing that reduces subsequent beetle attack.
This is sometimes referred to as “beetle proofing” a stand and should be
considered a “holding tactic” rather than a silvicultural system. Currently, this
technique is acceptable for management of mountain pine beetle only. This
technique is not applicable on a widespread basis and suitable stands must be
carefully selected.
Suppression
Suppression is the most aggressive of the available strategies. It is selected when
the infestation status is such that aggressive direct control actions are expected to
keep an area at a low level of infestation. The strategy demands that each
infested polygon be addressed. All possible direct control tactics (treatments)
should be considered and applied where suitable. Long-term approaches to
reducing future threats to timber or other resources should also be applied.
Suppression is the appropriate strategy for lightly infested areas where resources
for direct control or harvesting and milling capacities equal or exceed the
amount of infestation. Access must exist or be imminent. The strategy demands
detailed detection and follow-up every year to ensure complete sanitation of
infested stands. The intent of the strategy is to reduce the outbreak to a size and
distribution that can be handled with normal resources. In most cases, this
objective should be achievable within a three-year time span.
Maintain low
The maintain low strategy is applicable in chronically infested stands where the
spread of the beetle has been reduced to a level that can be dealt with under a
base or normal level program and within the allowable annual cut. This also
includes areas where the outbreak has collapsed but where extensive susceptible
stands remain. The strategy can be considered as a sub-set of suppression. The
intent is to accommodate expected beetle activity in the normal planning process
and to deal with new infestation polygons as they arise. Detection is critical for
application in harvesting programs and other treatments. All major access will be
in place or planned in conjunction with hazard rating.
A maintenance program will incorporate all relevant activities to prevent rapid
increases in the beetle population. A maintain low program is a base level
program and would continue indefinitely.
Holding action
The intent of a holding action strategy is to maintain an existing outbreak at a
relatively static level. It is a delaying strategy until adequate resources are
available or access created, allowing for more aggressive management. This
strategy is appropriate in areas with chronic beetle infestations, some of which
are too large to deal with using single tree treatments, or where access is poorly
developed for directed harvesting. Holding action would be recommended for a
BMU or a sub-unit where aggressive suppression would be appropriate but the
unit has a lower priority than other areas. It could also be used where resources
are inadequate to deal with all infestations.
A holding action is a temporary strategy and should not be maintained
indefinitely. There must be a clear time horizon for access development to
permit more aggressive sanitation harvesting and for the application of other
control options. Depending on the hazard and risk of the area, the infestations
should be dealt with in two to three years.
Salvage
This strategy is applied to areas where management efforts would be ineffective
in substantially reducing the beetle population and subsequent levels of damage.
Areas where a salvage strategy is appropriate usually have extensive outbreaks
covering a large proportion of susceptible stands and where access is planned or
possible within a five-year period. Infested areas will have relatively high
proportions of red and gray attack indicating that the outbreak has been ongoing
for several years. Smaller, moderate, or low hazard stands are commonly infested.
BMUs with a salvage strategy are basically left alone and no resources are
allocated to control. As harvesting capacity becomes available, timber in these
areas can be salvaged and the sites returned to production. Long-term
silvicultural strategies would be implemented at this point.
Abandon (no control)
This strategy is applied to areas where management efforts would be ineffective
in substantially reducing the beetle population and subsequent levels of damage,
or where there is no short term (less than five years) possibility of salvaging
dead timber. This may be due to management constraints such as wilderness or
parks, or because access cannot be put in place before substantial merchantable
degradation of the dead material occurs.