Douglas-fir beetle management
Douglas-fir beetle is relatively easy to predict and treat if consistently monitored and detected early.
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Aerial surveys are used for initial detection, but must be followed up with ground surveys to determine management recommendations.
All mapped infestations of three or more infested trees should be ground-checked to verify beetle activity and determine the infestation size.
Walkthroughs confirm the previous or suspected identification of beetle and host, collect information to set further survey or management priorities, and estimate population trends.
Probes provide more detailed information than walkthroughs and may be appropriate for laying out treatment areas. These systematic strip surveys provide more precise estimates of attack levels, beetle trends and residual stand values.
Star probes can be used to quickly map the extent of beetle infestations for small scale rapid treatment.
Strategies depend on several factors:
- Infestation size
- Stand susceptibility
- Forest values
- Site access
- Infestation history
The following framework describes the decisions and steps between from ground survey results to follow-up treatments.
Selection of an appropriate option depends on stand condition, level of infestation, condition of adjacent stands, ease of access, and management objectives for the area. Four resource management methods for Douglas-fir beetle are available:
Pest reduction harvesting
Pest reduction harvesting maximizes removal of currently infested Douglas-fir to reduce the existing population and inhibit infestation expansion.
All trees containing live beetles should be harvested and processed before adults emerge in the spring.
Trap trees are large, healthy Douglas-fir trees are felled into to attract and absorb emerging beetles. They must be removed and processed before adult beetles emerge in the spring.
Single infested trees can be removed when the infestation is small and localized. Single trees or small groups of infested trees can also felled and burned in place.
Hazard and risk rating
Hazard rating identifies stands where substantial losses can be expected if an outbreak occurs, and which are highly susceptible to attack. Once all Douglas-fir stands in an area have been rated, resources can be directed to those with the highest hazard, so losses can be minimized. Hazard rating considers stand age, host tree size, stand density, elevation, and other factors.
Stand risk is the probability the Douglas-fir stand will be attacked, based on proximity to a current infestation. Risk of attack may be determined by comparing aerial and ground survey information to hazard ratings.
After hazard and risk ratings are completed, management strategies can be developed.
The following factsheet provides information on how to manage Douglas-fir beetles and fire.