[Bark Beetle Management Guidebook Table of Contents]

Mountain pine beetle

Hazard rating

 Hazard rating is a valuable planning tool that identifies those stands where substantial losses can be expected if an outbreak of mountain pine beetle occurs. Once all pine stands in an area have been rated, resources can be directed toward those with the highest hazard so that losses can be minimized. Hazard rating considers stand age, host basal area, stand density, and elevation.

Hazard rating for mountain pine beetle requires inventory and location information. Data must be collected from prism plots in the field in order to precisely calculate the hazard index. Ten plots spaced at 100 m intervals will suffice if the stand is fairly uniform. However, if the stand is quite variable between plots, then a minimum of 20 plots should be sampled. The following must be recorded:

When the data are available, the hazard index is calculated using the formula:

HAZARD = P * A * D * L

where

P = per cent of susceptible pine basal area
A = age factor
D = density factor
L = location factor.

Methods for determining these factors are provided below and in Tables 5, 6, and 7.

P = % of susceptible pine basal area

A = age factor

Table 5. Age factors for mountain pine beetle hazard rating

D = density factor

Table 6. Density factor for mountain pine beetle hazard rating

L = location factor is determined by calculating Y and finding the factor in Table 7:

Y = (24.4 X longitude) - (121.9 X latitude) - (elevation (m)) + (4545.1)

Table 7. Location factor for mountain pine beetle hazard rating

Stands that are leading in lodgepole pine type, aged sixty years and older and that have the elevation, latitude and longitude code equal to high, should be considered a high priority for hazard rating and management.

Risk rating

Risk rating estimates the probability of an outbreak arising and is dependent on the proximity of a particular stand to an existing beetle population source. The risk of attack in any area can be determined by overlaying detailed sketch mapping and available ground detection results, on a forest cover map that has been coded for hazard.

Mountain pine beetle risk is a dynamic factor and is prone to change suddenly if climate conditions fluctuate or if there is an immigration of beetles from another area. It is related to the size and proximity of a beetle population affecting the stand being assessed. To arrive at a risk rating, the size of infestation and the distance of the infestation from the stand being assessed must be measured. Because beetle risk is a variable factor, it should be calculated annually or biannually.

Once both risk and hazard are known for stands within a planning area, individual stands can be ranked for survey, treatment, or other action. The resultant priority listing for actions can then be determined using Table 8.

Table 8. Determining priority for action based on stand hazard and associated risk

The most important use of determining the probability of an outbreak is in the planning and development of areas not currently heavily affected. Where beetle infestations exist, the risk is high and the hazard is determined by the stand parameters. This will provide information as to the potential for spread.

Ground detection

There are two types of ground surveys: walkthroughs and probes. These surveys vary in intensity, quality, and quantity of data collected. They are necessary to confirm information gathered from aerial surveys. Ground surveys obtain data on levels of current (green) attack and amount of remaining susceptible host material. Data are used to delineate infested areas and make decisions as to the most appropriate treatment.

In all cases, probes and walkthroughs should tally all stems tree greater than or equal to 7.5 cm dbh. Table 9 indicates when each type of survey is appropriate, based on preliminary information on infestation intensity obtained from the annual aerial overview. It is not necessary to ground check areas where no beetle activity was noted in aerial surveys.

Table 9. Recommended ground survey method and intensity based on infestation ratings gathered from aerial surveys

Walkthroughs are non-systematic preliminary ground reconnaissance surveys. They are preliminary surveys done prior to probes being completed. Walkthroughs are usually the first survey done in a stand. They locate and delineate spatially discrete pockets of infestation. Walkthroughs are often all that is needed for areas showing new infestations (spots). In areas with higher or more scattered levels of recent attack, walkthroughs may indicate a more detailed survey is required (Table 9).

Collect or estimate the following information during a walkthrough:

Attack centres are identified during a walkthrough. These surveys should also consider a variety of values at risk.

Probes are systematic, strip-type surveys which continue through a stand until no more infestation is noted or until a timber type change. Probes collect more detailed stand and infestation data than walkthroughs. Minimum data that must be collected and tallied for each infested polygon are:

When running a probe, ensure that:

Management options

 Tactics are equivalent to treatments and are applied to specific areas or infestations within a management unit. Most treatments will have to be repeated each year that the strategy remains in place. Unless the nature of the forest is changed, the susceptibility, and often the risk of subsequent infestation, will be similar from year to year. Figure 4 illustrates the decision-making process to select the most appropriate strategy for managing mountain pine beetle in a specified area.

Figure 4. Selection of management strategy for mountain pine beetle.

Activities for dealing with mountain pine beetle occur throughout the year. However, biology of the insect and local climatic factors will dictate when specific activities can be implemented. Further, the timing of some activities must take into account subsequent activities. For example, probing must precede harvesting but must be carried out early enough so that priority stands can be harvested prior to the next insect flight period. The timing of various activities for managing mountain pine beetle are given in Table 10.

Table 10. Annual schedule of mountain pine beetle management activities

Baiting

The use of aggregating semiochemicals (pheromone baits) has greatly facilitated efforts to reduce losses caused by the mountain pine beetle. Any placement of baits must have a subsequent treatment plan in place. Baiting stands prior to harvest, or other treatment, will reduce the spread of local populations of beetles, thereby reducing the size of sanitation cutblocks and greatly reducing the time and effort required to detect and delineate infested portions of stands. The use of baits must always be followed by actions to remove or eradicate the concentrated beetle populations. There are three uses for aggregating baits:
  1. contain and concentrate
  2. use with single tree treatments
  3. monitoring.
Contain and concentrate – Baits are placed throughout a target stand on a 50 m grid to facilitate sanitation harvesting. Baits are placed prior to beetle emergence. The intent of this pattern is to restrict the dispersal of beetles out of the stand and to concentrate their distribution within the stand. This facilitates sanitation harvesting, ensuring that the greatest number of beetles are removed, thereby reducing the local population available to infest adjacent stands.

Use with single tree treatment – Baits placed in single tree treatment areas will localize any residual beetles and facilitate subsequent treatments. In effect, the use of baits will preselect the sites for treatments such as MSMA where timing of application is critical for success.

Monitoring – Baits can be used to monitor the timing and duration of the beetle flight period. Such monitoring is helpful for timing MSMA application and to determine the period when hauling restrictions are necessary. To monitor beetle emergence:

Have a contingency plan for any spillover attack which occurs (e.g., MSMA).

Baiting strategy selection

A number of factors must be considered when selecting a bait-use strategy in a particular area. These factors are:

General guidelines for baiting patterns in a variety of circumstances are:

A. Uninfested drainage

1. Low to moderate risk (prevention strategy)

i. no access – baits should not be placed in inaccessible stands where existing beetle populations are negligible.

ii. access available – baiting is not recommended.

2. High risk (prevention strategy)

i. no access – baits should not be placed in inaccessible stands where existing beetle populations are negligible.

ii. access available – grid bait for one year only, prior to harvest, with the guarantee of harvest within the one-year period.
B. Infestation exists in some or all stands in a drainage.
1. Drainage mostly uninfested (suppression or maintain low strategy)

i. isolated spot infestations – spot baiting to restrict dispersal; limited grid baiting only in infested portions of stands and must be done in conjunction with application for a cutting permit or other treatment.

ii. some occurrences of patch infestation – spot baiting of any discrete clumps of infestation; grid baiting of patches with assured harvest or other treatment. Any particular stand should not be grid baited any longer than two consecutive years if harvest cannot be done in the first year.

2. Drainage generally infested (maintain low or holding strategy)

i. many stands affected with spot or patch infestations – sanitation harvesting with small block extraction, where possible, utilizing grid baiting. To maximize the sanitation effect of harvesting, ensure that grid baiting is done in smaller discrete blocks that address concentrated areas of infestation within affected stands. Spot bait to hold areas with lower levels of infestation for harvest or other treatment within one year.

Harvesting

Harvesting is the most efficient short-term method of dealing with mountain pine beetle populations where appropriate and practical. Any and all harvesting methods and systems are applicable in various situations. In all cases, the intent is to remove as much infested material as possible while meeting management objectives.

Sanitation harvesting

Sanitation harvesting is directed at reducing beetle population levels by logging. Priorities for harvest are determined from aerial and ground surveys regarding levels of infested pine. Stands with the highest levels of new attack and with a high potential for continued spread should receive the highest priority for removal (Table 8). Sanitation harvesting includes all harvesting methods such as clear-cutting, shelterwood, and selective cuts. Long-term preventive strategies should be implemented at the time of harvest to create non-susceptible or less susceptible stands in the next rotation.

Salvage harvesting

Salvage harvesting is directed at the removal and processing of dead timber before the wood has degraded below merchantability. Priorities for salvage cutting are determined on the basis of the levels of old attack in the stand and the age and quality of the timber. Long-term preventive approaches should be implemented at the time of harvest and at subsequent stand establishment. Maintenance or enhancement of species diversity should be kept in mind when developing prescriptions.

Harvest priority rating system

It is necessary to establish a method to determine stand harvest priorities so that the heaviest beetle concentrations can be removed first. This is especially important when harvest or milling capacity is insufficient to address all beetle infestations. Harvest priorities for beetle control will range from high, where beetles are active and the risk to adjacent stands is high, to low in the case of stands deemed as salvage. Criteria to be used for determining harvest priorities include:

High hazard host removal

Removing uninfested, high hazard host is a preventative measure. This approach involves long range planning to direct harvest to areas with the highest hazard. High hazard stands are removed prior to being infested. Susceptible host is removed on a priority basis thus preventing the onset or spread of attack. Harvesting of such uninfested wood is appropriate in either uninfested or lightly infested management units. High hazard host removal is a lower priority than removing beetle populations. All harvesting methods may be appropriate. Ensure long-term prevention options are employed following a landscape level plan that maintains or enhances stand diversity and biodiversity.

Single tree treatment

Layout of single tree treatment areas requires detailed detection surveys. Normal walkthrough or probe information is usually not adequate to achieve complete treatment as virtually all infested trees must be found and treated. A variety of single tree treatments exist that are intended to destroy beetles in infested trees, thereby reducing the available beetle population to infest new trees. The success of single tree treatments is dependent upon the correct timing and method of application. Thoroughness is required to ensure that a substantial portion of the beetle population is removed in a single tree program. All treatments require periodic spot checks to ensure and measure efficacy. Monitoring and possible re- treatments are necessary.

Small opening and single tree selection

Small opening and single tree extraction is the preferred single tree treatment method. Small infested patches, preferably less than 1 ha in size, but as large as 2 ha, may be cut, removed and processed. In a given geographic area containing low level, scattered or spot attacks, individual infested trees can be removed and utilized.

MSMA (Monosodium methanearsenate)

Trees selected for treatment with MSMA must be treated within three to four weeks of initial attack by the mountain pine beetle depending on local conditions and beetle development. MSMA is applied using the following procedure:

Fall and burn

This direct treatment is used to eradicate small spots or patches of infested trees in lightly infested areas, scattered attack on the periphery of larger infestations, and in areas where other resource constraints limit other treatment options. The following criteria apply: This treatment can be applied throughout the year, exclusive of fire season.

Topical insecticide

Topical insecticides are treatments that will protect high value trees from attack or kill beetles emerging from infested material. Treatment is required annually. Preventive sprays are applicable in campsites, urban areas, and in other highly specialized circumstances. Registered insecticides include Sevin® and Dursban®.

For pre-attack treatment to protect standing, living, high value trees:

For post-attack treatment to kill emerging adults and protect surrounding trees: Apply sprays as instructed on the pesticide label and directions.

Debarking

Attacked trees may be felled and debarked. This treatment is not applicable once the beetle brood have passed the pupal stage.

Hauling restrictions

Hauling restrictions may be necessary if points of destination of cut, infested timber, are located in uninfested drainages containing substantial amounts of high hazard timber. Such restrictions are necessary for as long as the emergence and flight period lasts. For scheduling purposes, select a start date in advance of the flight period, (e.g., July 15th). Removal of the restriction is based on Lindgren® funnel trap monitoring or an arbitrary date, such as August 20th, when the majority of beetle flight is complete.

Prevention

Prevention techniques are applicable to a large area of uninfested or lightly infested timber with a moderate to high hazard rating. The intent of the strategy is to reduce losses through manipulation of forest cover. Long-term management includes plans aimed at creating or maintaining age and species mosaics resistant to the mountain pine beetle.

Prevention strategies also indicate that harvesting plans should be based on existing hazard and risk criteria. That is, stands with the highest hazard and closest to beetle populations centers (high risk), should be logged or modified on a priority basis. The overall strategy is to remove the susceptible beetle host in an organized manner that will not create extensive and continuous stands of susceptible forest over the next rotation.

Beetle proofing

Prevention also relates to reducing the hazard of a particular stand or to reducing its attractiveness to the beetles through partial cutting. Partial cutting lodgepole pine stands is not a cure for the mountain pine beetle, but simply a holding tactic for suitable stands until a regular harvesting and management cycle can be resumed.

This could also be considered a “tactic” to be incorporated into all strategies presented above. The most common method is to selectively log a stand to a pre- determined spacing that reduces subsequent beetle attack. Four-metre spacing is adequate to reduce subsequent mortality caused by mountain pine beetle.

This technique is not applicable on a widespread basis and suitable stands must be carefully selected. Stands suitable for such treatment should be identified at the time of developing a landscape level plan.

Stand criteria for beetle proofing

The following guidelines provide site attributes to consider when evaluating a lodgepole pine stand for the application of beetle proofing. The criteria are inclusive; that is, the stand is most suitable for this treatment when all given criteria are in effect.

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