[
Root Disease Management Guidebook Table of Contents]

Evaluation and final prescription

Survey methods and threshold levels for prescriptions

For any combination of root disease and selected survey method, there are three broad disease incidence ranges each relating to a different level of disease treatment (minimal, alternate or intensive). In general, treatment intensity should increase in relation to disease incidence. Due to the potential “flushing” nature of Armillaria, this disease should be treated intensively wherever practicable, given resource management objectives. A unique set of disease management strategies and tactics is recommended for use in prescriptions in order to maintain favourable conditions for tree growth. These strategies and tactics are outlined in Tables 6 and 8.

There are currently no formal survey or management thresholds for Annosus or blackstain root diseases. Survey results for these diseases may be recorded in stand opening files, but no treatment options are currently recommended. If these diseases are present on your sites, consult your regional forest pathologist.

Table 4. Disease incidence and treatment levels by root disease and survey method for silviculture prescriptions

Table 5. Disease incidence and treatment levels by root disease and survey method for stand management prescriptions

Minimum treatment levels by root disease

Site ecology should be given paramount consideration when creating prescriptions for managing root disease. Forest health treatments should be prescribed to maintain or enhance identified resource values. To ensure the long-term integrity and productivity of forest ecosystems, biological and ecological considerations should be the minimum constraining criteria used when determining the need for, and selection of, a treatment.

For silviculture prescriptions

Refer to Table 4 and Table 6 for clarification on disease treatment levels and options. For host species susceptibility, consult Table 1.

  1. Armillaria root disease
    (a) Minimal disease treatment level:

    There are no restrictions on harvesting or regeneration strategies. However, unless Armillaria is completely absent from the stratum, consideration should be given to prescribing for tolerant or moderately susceptible species.

    (b) Alternate disease treatment level:

    Prescribe moderately susceptible or tolerant species for regeneration where ecologically appropriate. Where planting is prescribed, an alternating mixture of species should be considered. Planting of highly susceptible species is not recommended where susceptible host tree roots have not been removed.

    Partial cutting systems should be used only where clearcutting or group selection cannot be applied due to constraints imposed by other resource values, the site, or where inoculum reduction can be achieved via stumping or push-over harvest.

    (c) Intensive disease treatment level:

    Push-over harvest or harvest conventionally and stump the stratum to reduce inoculum, and regenerate with any desired species. Group selection or partial cutting will not be applied within this stratum unless inoculum reduction is done via stumping or push-over harvest.

  2. Phellinus root disease
    (a) Minimal disease treatment level:

    There are no restrictions on harvesting or regeneration strategies. However, unless Phellinus is completely absent from the stratum, consideration should be given to prescribing for moderately susceptible, tolerant or immune species.

    (b) Alternate disease treatment level:

    Prescribe moderate, tolerant or immune species for regeneration where ecologically appropriate. Where planting is prescribed, an alternating mixture of species should be considered. Planting of highly susceptible species is not recommended where susceptible host tree roots have not been removed.

    Partial cut systems, within strata prescribed to be regenerated with highly or moderately susceptible species, should be used only where clearcutting, group selection, or group shelterwood cannot be applied due to conflicts with other resource values, site constraints, or where inoculum reduction can be achieved via stumping or push-over harvest.

    (c) Intensive disease treatment level:

    Push-over harvest or harvest conventionally and stump the stratum to reduce inoculum, and regenerate with any desired species. Group selection or partial cutting should not be used unless inoculum reduction is achieved via stumping or push-over harvest. Where this cannot be achieved, regenerate with tolerant or immune species. Consider moderately susceptible species only if planted as a minor (<20%) component.

  3. Tomentosus root disease
    (a) Minimal disease treatment level:

    There are no restrictions on harvesting or regeneration strategies. However, unless Tomentosus is completely absent from the stratum, consideration should be given to avoidance planting around infected stumps.

    (b) Alternate disease treatment level:

    Prescribe moderately susceptible, tolerant or immune species for regeneration where ecologically appropriate. Planting of highly susceptible species is not recommended where susceptible host tree roots have not been removed.

    Avoidance planting, using highly susceptible species, can be done providing minimum stocking targets can be met (given the reduction in plantable spots resulting from a 5 metre radius buffer around infected stumps).

    (c) Intensive disease treatment level:

    Push-over harvest or harvest conventionally and stump the stratum to reduce inoculum, and regenerate with any desired species. Group selection or partial cutting should not be used unless inoculum reduction is achieved via stumping or push-over harvest.

  4. Annosus and blackstain root diseases

    Where Annosus and blackstain root disease are found in close association with any of the above mentioned root diseases, inoculum reduction may be undertaken. Otherwise, prescription of alternate less susceptible species is recommended.

For stand management prescriptions

Refer to Table 5 and Table 8 for clarification on disease treatment levels and options. For host species susceptibility, consult Table 1.

  1. Armillaria root disease
    (a) Minimal disease treatment level:

    There are no restrictions on stand management operations. However, unless Armillaria is completely absent from the stratum, consideration should be given to favouring tolerant or moderately susceptible species as crop trees where ecologically appropriate.

    (b) Alternate disease treatment level:

    Review this option carefully. For those stand management operations that would result in the creation of living stumps and increase the inoculum level in a strata, it is recommended that the district manager only approve prescriptions required to fulfill the obligations of basic silviculture. These activities would include manually thinning strata with stocking above maximum density levels, while restricting highly susceptible host species to <20% of stratum composition. Also, restricting manual brushing only to that critical for preventing crop tree mortality. Further, manual brushing whose sole objective is promoting conifer release should not be approved. It is recommended that the district manager consider accepting a reduction in conifer growth as any manual brushing activity will likely result in increased conifer mortality.

    No stand tending operations that would result in increased inoculum levels in a stratum are recommended. These activities include thinning of stands below maximum density levels and non-critical brushing. Activities such as pruning for value and stand fertilization should be carefully considered before approval. Treatments should be conducted only on trees that are most likely to become crop trees and that are most tolerant to the disease.

    (c) Intensive disease treatment level:

    No stand tending operation should be prescribed in strata exhibiting this level of infection unless an inoculum reduction treatment is conducted. It is recommended that the district manager consider accepting reduced levels of stocking within a stratum or, in extreme conditions, consider rehabilitation of a stratum. Activities may be considered where the objective is to improve survival from another pest (e.g., pruning Pw to avoid white pine blister rust) so that a tree species may reach a size suitable for early harvest.

  2. Phellinus root disease
    (a) Minimal disease treatment level:

    There are no restrictions on stand management operations. However, unless Phellinus is completely absent from the stratum, consideration should be given to favouring immune, tolerant or moderately susceptible species for retention where ecologically appropriate.

    (b) Alternate disease treatment level:

    Review this option carefully. For those stand management operations that would increase the inoculum level within a stratum stocked mainly with highly susceptible species (>60% stand composition) following treatment, it is recommended that the district manager only approve prescriptions required to fulfill the obligations of basic silviculture. These activities would include manually thinning stands with stocking above maximum density levels.

    No stand tending operations that would result in increasing inoculum levels are recommended within strata where the resulting stand will be composed of mainly (>60%) highly susceptible species. These activities include thinning of stands below maximum density levels. Activities such as pruning for value and stand fertilization should be carefully considered before approval. Treatments should be conducted only on trees that are most likely to become crop trees and that are most tolerant to the disease.

    For strata with anticipated post-treatment stocking of mainly (>60%) immune, tolerant, or moderately susceptible species, any stand tending activities required should be prescribed and conducted as per normal.

    (c) Intensive disease treatment level:

    No stand tending operations should be prescribed in strata with stocking of mainly (>60%) highly and moderately susceptible species and exhibiting this level of infection, unless inoculum reduction treatment is also applied. It is recommended that the district manager consider accepting reduced levels of stocking within the strata or, in extreme conditions, consider rehabilitation of the stand. Activities may be considered where the objective is to improve non-host tree survival from another pest (e.g., pruning Pw to avoid white pine blister rust).

  3. Tomentosus root disease

    (a) Minimal disease treatment level:

    There are no restrictions on stand management operations.

    (b) Alternate disease treatment level:

    Review this option carefully. Favour immune, tolerant or moderately susceptible species for retention as crop trees where ecologically appropriate. When thinning using conventional means, favour immune, tolerant or moderately susceptible species and consider restricting highly susceptible host species to <40% stratum composition.

    (c) Intensive disease treatment level:

    No stand tending operations should be prescribed in strata exhibiting this level of infection unless inoculum reduction treatment is conducted or the stand is converted to mainly tolerant or immune host species (>60% stratum composition).

  4. Annosus and blackstain root diseases

    There are no restriction on stand management operations where these are the sole root diseases located in a stratum. Where Annosus or blackstain root disease are found in close association with any of the three other mentioned root diseases, consider the total stand incidence level for all root diseases and act according to the recommendations discussed above.


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