[Root Disease Management Guidebook Table of Contents]
Management of root disease
Root disease management process
Root disease management is not designed to be a process unto itself, but rather to be integral to the established process of evaluating forest stand and site conditions. This approach minimizes the risk to resources and management objectives. The following section details recommended actions which are intended to assist the user in detecting and evaluating root disease incidence, and in using this knowledge to develop viable plans and prescriptions.
The five-phase procedure below integrates the evaluation of stand, site, and disease conditions for the purpose of creating a prescription (Figure 7).
- Landscape level hazard and risk assessment
- Prescription walkthrough reconnaissance
- Disease assessment and stratification survey
- Future stand risk assessment
- Evaluation and final prescription.
These steps are discussed in detail in the following sections.
Figure 7. Diagram of root disease management process.
Landscape level hazard and risk assessment
In order to develop a prescription that adequately addresses root disease, two levels of hazard and risk assessment are required. These are: (1) a landscape level hazard and risk assessment, and (2) a future stand risk assessment (see section on “Future stand risk assessment”).
The landscape level hazard and risk assessment should also be included in forest development plans or other higher-level plans where they exist.
The landscape level hazard and risk assessment considers two key factors:
- the hazard inherent in the ecosystem at the biogeoclimatic subzone level and the susceptibility of the indicated forest cover
- the risk (or probability of root disease and its expected damage impact) in a polygon or block.
Both of these factors have been considered by regional forest pathologists and are compiled into tables in the Appendices. Each table identifies regional high hazard biogeoclimatic subzones that have a high probability of root disease occurrence and which will require evaluation as part of the prescription process. Landscape level hazard and risk assessment is an office exercise that provides a reasonable level of guidance as to what to expect on a site, but in no way is to be considered the sole evaluation.
The prescription walkthrough is an essential step in the root disease management process and provides an early opportunity to evaluate stand hazard and risk, as well as the general incidence of damaging agents. More information on formulating stand and landscape level hazard and risk can be found in the Forest Health Surveys Guidebook. The intent of the walkthrough is to provide a preliminary stratification of the site.
A proper walkthrough may provide information for the deliniation of strata which obviously are outside the minimum or maximum threshold levels for root disease management. If root disease incidence is obviously above the maximum threshold level, then prescribe the appropriate disease treatment for that strata without conducting further formal surveys. If the site is below the minimum threshold level, then a formal root disease survey is only recommended for high hazard ecosystems (see the Appendices). For strata which fall between the minimum and maximum thresholds, a recommendation for a more formal survey may be made on the basis of disease distribution and intensity detected in the walkthrough.
The disease management threshold levels are described in the section on “Survey methods and threshold levels for prescriptions.”
Disease assessment and stratification surveys
Several formal stand level survey methods (described in the section on “Disease assessment and stratification survey methods”) can be used to assess and stratify root disease both prior to and following harvest or stand tending. All methods have their strengths and weaknesses and differ in their ability to provide an accurate estimate of root disease. For this reason there are different threshold levels for disease incidence and treatment decision-making which vary depending on the survey method used (see section on “Evaluation and final prescription”).
The following stand-level survey methods (with the root disease most suited for detection by this method in brackets) are covered in this guidebook.
- Intersection length (Phellinus in coastal stands only)
- Sketch mapping (Armillaria, Phellinus in coastal stands only)
- Line transect (all)
- Pixel (Armillaria, Phellinus in mature interior stands only)
- Intensity measuring pixel survey or IMPS (all)
- Stump top (Tomentosus).
Some of these surveys are new and experimental (e.g., IMPS, stump top). If a walkthrough indicates root disease presence which is below the maximum threshold level, the district manager or licensee is advised to recommend surveying the stratum concerned in order to document disease incidence and distribution.
More information on the application of these surveys is available from district and regional forest health staff. The district manager has final authority over any survey method used as part of the silviculture or stand management prescription data collection process.
For information on landscape level forest health surveys, please consult the Forest Health Surveys Guidebook.
Future stand risk assessment
Assessment of future risk to a stand is an essential component to be considered when developing a prescription. Assessing treatments to be conducted within the framework of a crop plan will help avoid future problems created by considering only short term gain. A future stand risk assessment should be conducted on any site for which a prescription is being created. The future risk for root disease is based on:
- the incidence level of root disease, by strata
- the existing and future host tree population (susceptibility, number, and size, successional stage, and desired future stand structure)
- the biogeoclimatic environment (subzone, variant, site series)
- the recommended disease management strategies and tactics
- stand management practices (past, present, and future) that have affected or may affect root disease incidence levels.
These latter four points essentially require the prescribing forester to evaluate the risk by considering the potential root disease management strategies and tactics as outlined in the sections on “Strategies and tactics for silviculture prescriptions” and “Strategies and tactics for stand management prescriptions.” The future stand risk assessment process is highly integrated with the procedure described in the section on “Evaluation and final prescription.”
Presently there is no quantitative decision support system that could be used to assist a forester in making this risk assessment. However, there is a conceptual model which can be used as a basis for risk assessment decision-making illustrated in Figure 8.
Figure 8. The forest health management triangle.
Evaluation and final prescription
This evaluation process is integral with the future stand risk assessment process. A root disease treatment evaluation should form a major part of any prescription where root disease is present. This process is perhaps more iterative than risk assessment, since for each disease incidence level there is a corresponding disease treatment level (minimal, alternate and intensive). This is more fully explained in the section on “Evaluation and final prescription.”
It is recommended that stand management objectives be adjusted where root disease incidence, site conditions, risks, or constraints dictate. This is preferable to prescribing an inappropriate root disease management treatment which places resource management objectives and future forest health at risk.
[Return to top of document]