Define Semivoltine
Two year life cycle
What are the Five Direct Control Tactics?
Which is most USED?
1) Burning
2) Mechanical Treatments
3) Sanitation Logging
4) Chemical Tactics
5) Semiochemical Tactics
Define Epidemiology
The study of the patterns, causes, and effects of health and disease conditions in defined populations
Describe Indirect Control?
MPB Management Stratagies
Treatments aimes at increasing stand vigour
Preventative management
Primarily done before the outbreak
Key princibles in application are the consistant use of well planed forestry practices
Define univoltinism
One year life cycle
What are Four Population Phases
Describe?
- Endemic - Principly in small DBH trees that are weakened. Interactions with other lower bole beetles is important for MPB establishment an survival
(Good chance at stopping it) - Incipient Epidenmic - Develop when larger diameter host trees can be successfully colonized (host resistance lowers or increase favorable breeding conditions or both)
Becomes more significantly difficult to stop at this stage - Epidemic - Exists at a landscape level.
Nearly impossible to stop at this stage - Post Epidemic - Populations decline due to adverse weather or depletion of host.
Describe Direct Control?
MPB Management Stratagies
Treatments aimed at reducing beetle populations.
Reactive Approach
Key princibles are timeliness and thoroghness
6 Effects of a Major MPB Outbreak
- Extensive timber loss (volume:decay/stunted growth. MPB hits tree before its reached merchantable value
value: more pulp, less saw log) - Increased fuel loading
- Altered successional trajectories
- Reduced watershed quality
- Altered wildlife composition
- Altered recreational values
Describe efficient dispersal as a Critical aspect of life history to establishment and survival of IBM
In stand, short range (30m or less), in canopy dispersal
Wide initial dispersal; Out of stand, long range (up to 300km) if carried by extreme, warm convective currents
Describe efficient host seletion as a critical aspect of life history for IBM
Efficient host selection:
COLONIZE LARGER STEMS (>20cm DBH);
Tree’s size main determinant of tree’s potential to produce beetles because of increased bark thickness (more bark scales, less breakage) and increased phloem thickness (lay more eggs=bigger brood=higher survival)
COLONIZE OLDER STEMS: the older the tree, more susceptible, older trees less capable to fight off blue stain fungus;
COLONIZE HIGHER DENSITY STANDS: Reduced tree vigor as density increases; MOre favourable microclimate for MPB as density increases; These stands are common due to fire suppression
Describe how highly evolved mutualistic relationship with blue stain fungi aids in overcoming host resistance for MPB
- Conflicts with optimum conditions because trees MPB perfers are healthy, blue stain helps to break down those defences
- Blue stain fungi is one of two defences (other is disruption of tree physiology via gallery creation in phloem)
- Blue stain is acquired and disseminated via adult beetle’s exoskeleton, fungal spores inoculated into trees as beetle bores; terminates trees resin defenses by causing dessication and disruption transpiration
- Blue stain fungi also assists MPB by: protecting broods from antagonistic fungi; improving moisture composition of phloem for larvae; providing nutrients to complete development
Describe how stage specific development thresholds ensuring synchrony of development in and among growing seasons are a critical part of MPB establishment
- Cold Tolerance:
largest single source of mortality in MPB;
Acquired through production and accumlation of glycerol;
Larvae are the most cold tolerant because they overwinter;
High amounts of adults survive winter and attack early, but the progeny they produce have little chance to contribute to population fluctuations because their life cycles dont coincide with greater MPB populations (mass attack)
Describe the relationship of Temperature to MPB’s life cycle
- life cycle stages delegated by stage specific responses to temperature;
- Emergence and dispersal, host selection and colonization, mating, etc occur late July to mid August;
- Larvae reach 3rd or 4th instar before temps are too cold to halt development, then resume feeding when temps warm in spring
- Complete development and transform to pupae by June
- Pupae are new adults by late June and mid July, need one or two weeks to mature and ready for emergence and dispersal
Discuss development rates specific to subpopulations that ensure one year life cycles over a large part of the geographical range
- MPB has evolved regional differences in development rates to adapt;
- Northern populations of MPB develop faster for a given input of temperature than southern populations
- adverse weather conditions won’t prevent outbreaks or reduce populations as long as univoltine life cycles are maintained
- In most northern and high elevation environments, MPB has become semivoltine, but populations aren’t expected to meet epidemic levels because:
higher mortality
exposure to natural enemies for longer periods
reduced colonization success because of reliance on ‘mass attack’
How can long term mitigation of large-scale epidemics be achieved?
Through management strategies that reduce Pl susceptibility over the landscape. Direct control not viable at epidemic levels, Indirect management becomes the only option.
Lodepole pine fire dynamics and MPB breakouts
- natural fire cycle for Pl in BC is 60 years-coincides with high stand susceptibility to MPB attack
- Intro of fire mgmt has allowed large numbers of fire suppressed stands to enter susceptible age class for MPB
- Result is 3x more susceptible Pl to MPB compared to pre-fire supression
Describe Climatic influences as an outbreak dynamic for MPB
- Favorable climate allows MPB to expand into previously unaffected areas
- Warmer temps increase beetle survival during winter and flight periods
- Tree and stand resistance reduced during drought periods
- Combined with fire dynamics, settings are ideal for MPB attack
- Susceptible Pl is transitional phenomena-unlikely large amounts of susceptible pine will be seen again
When are direct control tactics useful?
- Only when treated at endemic and possibly incipient epidemic phase
- MPB pops expand too quickly to control after a certain point-not economically feasible
3 management principles needed for direct control to have any chance of success:
- Early Detection
- Aggressive direct control tactics employed promptly and thoroughly
- Control programs must be continuous until the desired population level is achieved
As long as the character of the stand remains the same, future outbreaks may be expected whenever tree vigor is seriously reduced (eg:drought). Suppression failed in the past because the three principles weren’t followed.
Name the 4 main strategies used to control MPB epidemic in BC:
- Suppression/prevention: aggresive direct control tactics used to reduce populations to endemic levels
- Holding: Efforts aimed at keeping population levels at current level, until more resources are available or underlying cuase of infestation subsides
- Salvage: aggressive options unlikely to succeed so dead timber is recovered while it still holds value
- Monitor: only realistic and appropriate strategy in inaccessible or inoperable regions and in parks and protected areas
What are the two parts preventative mangement AKA indirect control can be broken down to
- Landscape planning to prevent expansion to epidemic outbreaks
- Stand management to prevent incipient infestations
What makes preventative management vital to have any chance to manage MPB outbreaks
- Fire suppression has increased area occupied by mature Pl in BC from 2.5 million ha to 8 million+ ha
- recent warming trends have expanded (and will continue to expand) range of MPB in BC
- Pl is largest contributor to commercial timber harvest in western Canada
- Difficulty high when trying to successfully implement direct control strategies when MPB pops exceed endemic levels
Three conditions needed for landscape level outbreak to occur:
- Several years of mild winters and warm, dry summers, leading to small patch incipient infestations
- Some of the incipient infestations must develop unchecked by weather or mgmt action to the point where high MPB numbers are produced
- Must be an abundance of susceptible stands on landscape to sustain high beetle populations
What’s the basis of long and short term planning for MPB?
Long term planning: requires ranking of pine stands based on relative susceptability
Short term planning: requires ranking of stands for risk of significant loss over the short term
