Understanding and Managing Sudden Oak Death in California

2.3.1. Prioritization Categories

Management opportunities—

You can readily identify low priority sites by determining which areas are not feasible to treat. These include areas that are so steep and/or inaccessible that treatments would be excessively difficult and expensive. Areas that are not practical to treat can be removed from further consideration.

Among sites that could be treated, the ease of treatment and likelihood of obtaining acceptable levels of disease control will vary due to the factors shown in table 2-7. By assessing these factors, you should be able to rank potential sites based on their overall SOD management opportunities.

Table 2-7—Prioritization matrix: Factors to consider when prioritizing stands for SOD management activities

Category Factors Priority for management action



High Priority Low Priority


Ease of access for treatment (slope, roads, etc)

Near level

Excessively steep

Adjacent to roads

No road access

Position of treatment area

A rea is discrete unit, little or no likely contribution of inoculum from adjacent areas beyond treated zone

Area is adjacent to areas that cannot be treated

SOD impact stage

No or low percentage of trees with cankers or SOD mortality

High percentage of trees dead or with severe SOD symptoms

Relative cost of treatment

Low cost per unit treated

High cost per unit treated

Overall likelihood of success

L ikely to be successful due to combination of favorable site and/or logistical factors

Low probability of success due to difficult site and/or logistical factors

California bay presence/density/sizeclasses

Bays mostly understory saplings and small trees

Bays are large overstory trees

Bays are low percentage of total tree cover

Bays are majority of tree cover

California bay continuity

Bay distribution discontinuous in local area or could be made discontinuous with limited tree removal

Continuous bay distribution over large area, little or no possibility of creating significant gaps in distribution

Disease Risk:

California bay density

Low to moderate density in overstory and/or understory

None present within stand

Proximity to known P. ramorum infestations

P. ramorum present in stand

Nearest known P. ramorum at least 8-16 km (5-10 mi) away

Risk of pathogen introduction (if not present)

High number of visitors and vehicles

Infrequently used site

Climate / microclimate conditions

Wet -rainy, foggy, north facing slope, dense tree canopy

Dry - fog uncommon, south facing slope, open canopy


Tree variables

Large, dominant, vigorous trees with thick, expanding bark (bark fissures with brown, unweathered tissue)

Small, overtopped/suppressed, and/or water- stressed trees with thin bark, slow bark expansion (bark fissures weathered and grayish)

Resource benefits:

Stand condition without SOD

Sustainable stand, trees mostly fair to good condition

Stand declining due to other factors

Stand uniqueness

Stand unusual due to species composition, age structure

Widespread and common stand type

Historical / cultural value

Significant trees or stand

No special significance

Aesthetic /amenity/ visual values

Significant scenic resource

Stand not within a viewshed

Strongly contributes to property value

Low or no specific contribution to property value

Serves as visual buffer (e.g., screening, privacy)

No visual buffer effects

Habitat value

Essential or preferred habitat of rare or special status species.

Unsuitable habitat for rare or special status species, none present.

Important habitat for other locally significant or desirable species

Poor habitat quality for species of interest

Special habitat features/areas present (e.g., riparian, wetland, old growth, unique soils)

No special habitat features

High native species biodiversity

Low native biodiversity (e.g., highly disturbed site)

Important corridor or connection between different habitats

Doesn't function as corridor (e.g., isolated forest fragment)

Soil stability and water quality

SOD-susceptible species in critical location providing slope stability / erosion protection

SOD-susceptible species not important contributors to soil stability at site

SOD-susceptible species present along watercourse and providing important bank stabilization

SOD-susceptible species not near watercourse or don't contribute to bank stability

SOD-related liabilities

Hazards posed by infected and dead trees to persons and properties

Failures would affect occupied structures

Not near structures

Failures would affect heavily used roads or trails

Not near roads or trails

Failures would affect other built infrastructure (utility lines, drainage structures, etc)

Not near infrastructure

Contribution to fire hazard

Defensible space fire hazard significantly increased by fuels associated with dead standing or down trees

SOD-related mortality poses little or no change to overall fire hazard within or near defensible space

Conversion to exotic-dominated or other undesirable vegetation type

Highly susceptible to invasion by undesirable exotics

Invasion by exotics unlikely

Gaps likely to be converted to undesirable vegetation type

No undesirable changes likely due to species mix and small or no gaps


Disease risk—

Assessing factors that influence SOD risk can help you determine which sites to prioritize for treatment. If the risk that SOD will develop in a given stand is small, that stand will have a very low priority for SOD management activities. Disease risk may change over time as conditions change, so priority rankings based on disease risk need to be reevaluated periodically.

Loss of resource benefits—

Sites with at-risk SOD canker hosts can be prioritized by considering the various ecosystem services they provide. Highest priority sites provide the most important benefits and values. Table 2-7 lists a number of potential factors to consider. To develop a list that matches your management objectives and interests, add or delete items from table 2-7 and adjust the definitions of the high and low priority categories. The weight of factors can also be shifted.


The presence of many SOD-killed trees on a landscape may pose a number of hazards. Consider the degree to which you can avoid these hazards by preventing or minimizing SOD-related mortality when prioritizing sites for treatment.

Gathering information for decision making—

For large parcels, data from maps or GIS databases may be used to identify sites that can be eliminated from consideration (e.g., inaccessible areas) or to identify areas to examined in detail (e.g., significant areas with uncertain vegetation composition). Targeted surveys or observations may be used to obtain information needed to assess priority (e.g., the amount of SOD present).