Insect and Disease Risk Potential Assessment.pdf

Insect and Disease Risk Potential Assessment:

Transport of Fire-Damaged Timber Throughout the Western US

June 23, 2022

This whitepaper was produced by a team of Forest Health Protection specialists from across the west and led by the US Forest Service National Office. It represents the professional experience and assessment of currently available science and environmental conditions.

Background:

The USDA Forest Service is exploring a project for industry to move fire-damaged timber from several western national forests to distant milling infrastructure with the capacity to process the wood. This could increase utilization of fire damaged timber, reduce fuels, and support existing critical infrastructure that is necessary to support agency efforts to create resilient forests. A pilot project proposes to move fire-damaged ponderosa pine, Pinus ponderosa, logs from northern California, where there is a surplus of material and inadequate processing capacity, to the Black Hills in South Dakota where there is industry capacity to process the wood. The pilot project may also include moving other commercial conifer species to other destinations in the western U.S.

Pest Movement

While moving wood from one continent to another is often the greatest concern for moving insect and pathogen pests (for example, the emerald ash borer that is now eliminating ash trees in North America), moving them from one ecozone to another within a continent also presents risks.

Within the ecozones of the western US, there are a diversity of landscapes, forest types and associated insects and pathogens. While some of these insects and pathogens may occur across many ecozones, others are native to only one or two ecozones, and in some cases, only within a portion of an ecozone. Some are primary, and cause tree damage or mortality within the ecozones that they occur, while others are considered secondary or minor pests. Both known tree-killing pests, and secondary insects and pathogens, transported in logs to areas outside of their natural biogeographical range have the potential to cause unexpected and widespread tree mortality in a new habitat. Tree hosts that have not coevolved with a pest may lack adequate resistance, or there may be a lack of natural enemies. In addition, the extreme drought conditions experienced across the west have increased host tree vulnerability to insects and pathogens.

Two examples of native insects that have been moved from their native ranges are the goldspotted oak borer and the walnut twig beetle. Both are secondary insects where they occur naturally. Goldspotted oak borer was transported in untreated firewood from Arizona to California where it has become a serious pest of native oaks. Walnut twig beetle and thousand cankers disease were moved from the southwest and have killed planted black walnut trees in many western states. Because of such risks, the USDA Forest Service, USDA APHIS Plant Protection and Quarantine and partner state agencies have an ongoing education program and regulations to discourage movement of firewood (http://www.dontmovefirewood.org/wp-content/uploads/2022/04/FirewoodComparisonReport_11Apr2022a1.pdf ).

Movement of large quantities of whole unprocessed logs could result in an even more significant increased risk for movement of potential pests. This is especially true when these logs are being harvested within fire perimeters. Many of the major pest species of concern are opportunistic and will focus on trees that are stressed or damaged by fires, and even live undamaged trees within the fire perimeter. These trees are especially likely to harbor some of the major species of concern within the first 1-3 years following a fire.

The greatest threat posed by moving insects and pathogens among ecozones is from insects and pathogens that are known causes of tree mortality within their ecozones. Many of these aggressive tree killing species, such as mountain pine beetle, Douglas-fir beetle, spruce beetle, and several pathogens, occur throughout most of the west, however, other species have a much more restricted range, and occur within only one or two ecozones; these are the species of concern that can cause tree damage or mortality when moved to new ecozones.

A team of Forest Health Protection professionals (Bob Cain, Iral Ragenovich, Sheri Smith, Danny Cluck, Stacy Hishinuma, Joel McMillin, Gina Davis, Joel Egan, Frank Krist, and Bob Rabaglia) was assembled to identify ecozones in the west and assess potential risks and impacts of moving logs outside of these zones. The team identified nine primary insects and pathogens within each of these western ecozones and sub-ecozones that would be of most concern if moved outside of their native habitat (Table 1). The table also identifies a preliminary risk and impact for each. Appendix A details examples of the potential risks of moving two of the most important insects – the western pine beetle and the California fivespined ips – from California to other ecozones, especially the Black Hills in South Dakota.

Ecozones

Across the western US there are four broad ecozones (Figure 1). These zones are based on environmental conditions, forest types, tree species, and the ranges of the important insect and pathogen species. Generally, logs can be moved safely within the respective ecozones, or subzones. Two of the ecozones are broken into subzones that would limit movement without mitigation within the ecozones. The dotted area in the green zone from coastal California to southwestern Oregon is the area that is regulated for sudden oak death which restricts the movement of oak logs and other related forest products. Crosshatched areas within the blue and green zones, are subzones with pests of concern that are not currently known to occur in the rest of the ecozone. Logs within these ecozones could safely be moved into but not out of crosshatched or dotted areas. Movement of logs between ecozones is complicated by the direction of the movement and would generally require mitigation to reduce risk of moving pests.

Figure 1: Ecozones and subzones in western US based on environmental conditions, forest types, tree species, and the ranges of the important insect and pathogen species.

Ecozones and subzones are color coded and explained In Table 1.

Table 1. High risk insects and pathogens moving in conifer logs from ecozone of origin to a receiving ecozone

Ecozone of origin California, Western Oregon & Western Washington

Eastern Oregon, Eastern Washington, Idaho, Western Montana

Eastern Montana through Wyoming, South Dakota, Nebraska, Colorado, Utah, Nevada, and northen New Mexico Arizona and New Mexico

California, Western Oregon & Western Washington

California fivespined ips 5, Sudden oak death 4

California fivespined ips, Sixspined ips

California fivespined Ips, Western pine beetle, Balsam woolly adelgid 3

California fivespined ips, Balsam woolly adelgid

Eastern Oregon, Eastern Washington, Idaho, Western Montana Balsam woolly adelgid

Balsam woolly adelgid

Western pine beetle, Balsam woolly adelgid

Eastern Montana through Wyoming, South Dakota, Nebraska, Colorado, Utah, Nevada, and northen New Mexico

Eastern fivespined ips, Sixspined ips, Roundheaded pine beetle

Eastern fivespined ips, Roundheaded pine beetle

Southwestern pine beetle 1, Roundheaded pine beetle 2

Eastern fivespined ips, Western pine beetle, Balsam woolly adelgid

Arizona and New Mexico Arizona fivespined ips, Southwestern pine beetle, Roundheaded pine beetle

Arizona fivespined ips, Southwestern pine beetle, Roundheaded pine beetle

Arizona fivespined ips, Southwestern pine beetle 1, Roundheaded pine beetle

Common name: Scientific name: Hosts: Risk * : Impact:

Roundheaded pine beetle Dendroctonus adjunctus Pines High ecological impact high - economic impact high Southwestern pine beetle Dendroctonus barberi Pines High ecological impact - moderate Western pine beetle Dendroctonus brevicomis Pines High ecological impact high - economic impact high Sixspined ips Ips calligraphus Pines High ecological impact moderate - economic impact moderate Arizona fivespined ips Ips lecontei Pines High ecological impact moderate - economic impact moderate Eastern fivespined ips Ips grandicollis Pines High ecological impact low - economic impact low California fivespined ips Ips paraconfusus Pines High ecological impact moderate - economic impact moderate Balsam woolly adelgid Adelges piceae Firs Moderate ecological impact high Sudden oak death Phytophthora ramorum Douglas-fir, redwood Low ecological impact high; economic impact high

* - Risk is defined as the risk of movement and establishment of a species from one ecozone to another if no mitigation is implemented.

Movement of unmitigated logs outside of these subzones within the same ecozone may pose risk 1 - Southwestern pine beetle occurs in southern Colorado and Utah, but not the rest of this ecozone 2 - Roundheaded pine beetle occurs in southern Colorado and Utah, but not the rest of this ecozone 3 - Balsam woolly adelgid occurs in northern Utah, but not the rest of this zone 4 - Sudden oak death occurs in coastal California and coastal southwest Oregon, but not the rest of this ecozone.

5 - California fivespined ips occurs in California and Oregon but is not established in Washington

Receiving Ecozone

Mitigation Measures

There are various mitigation measures that can reduce the risk of moving pests from one area to another. Heat treatment, fumigation and debarking are the most commonly accepted methods for reducing risk in international trade. Although some insects, especially ambrosia beetles and woodborers, as well as some of the pathogens, can potentially be transported in the wood, the bark is the single most important habitat of the primary insect and pathogen pests. These occur either directly on, or in and under the bark. Debarking the logs before transport outside of an ecozone will significantly reduce the risk. Debarking standards that describe the minimum amount of bark that can be left on the logs after debarking to mitigate risk were developed. These standards are based on existing international and federal guides and regulations and inspection requirements for importation of timber and solid wood packing material.

Debarking Standards for Western Conifer Logs Transported Beyond the Primary Tree Killing Native Pest Ranges

The goal of debarking is to remove bark from logs to be transported to mills beyond the range of pests of concern to sufficiently reduce the risk of moving insects and pathogens.

Debarking is an effective means of managing phloem-feeding insects as it removes the food source and exposes the life stages to drying and predators. Wood boring insects that tunnel into the sapwood and heartwood of the tree will not be affected by debarking alone, but these insects pose less known risk to forests ecosystems than do phloem-feeding insects. Observation of partially debarked logs infested with mountain pine beetle in the Black Hills showed that beetles were not killed in areas where bark remained on the log. Therefore, debarking will need to be thorough and comply with accepted standards to effectively reduce risk.

There are existing guidelines for debarking raw logs for importing or exporting from countries. Debarking guidelines that focus on wood packaging material and lumber emphasize the need for bark removal to be thorough to be effective. The International Plant Protection Convention (IPPC) developed the ISPM 15 in response to the global threat of the widespread transportation of timber pests and diseases (https://ispm15.com/wp-content/uploads/2018/08/ispm15_international-standards-for-phytosanitary-measures_adopted-2013_published_2017.pdf). ISPM 15 states “Use of debarked wood irrespective of the type of treatment applied, wood packaging material must be made of debarked wood. For this standard, any number of visually separate and clearly distinct small pieces of bark may remain if they are: - less than 3 cm in width (regardless of the length) or -greater than 3 cm in width, with the total surface area of an individual piece of bark less than 50 square cm.” The USDA also addressed movement of wood in the Code of Federal Regulations in 7 CFR 319.40 -7 Treatments and Safeguards(B) Debarking. It states “Except for raw lumber, no more than 2 percent of the surface of all regulated articles in a lot may retain bark, with no single regulated article retaining bark on more than 5 percent of its surface. For raw lumber, debarking must remove 100 percent of the bark.”

Appendix A. Pest Risk Assessments for two potentially damaging insects if moved to a new ecozone

Western Pine Beetle

1. Probability of pest establishment: High likelihood of establishment if introduced (reasonably certain). Populations could be suppressed by extended temperatures below -20 but they can recover quickly when conditions are favorable or during warm dry periods. Temperatures below this range are uncommon in the Black Hills region.

2. Spread potential: High (reasonably certain). The uniform ponderosa pine host type would be favorable for spread in the Black Hills. The western pine beetle can aggressively attack and kill ponderosa pine trees of all ages and vigor classes that are 6 inches (15 cm) or larger in diameter, including apparently healthy trees. Group killing of trees is common in dense, over-stocked stands of pure, even-aged, young sawtimber, but also occurs among dense clumps of pine in stagnating mixed-conifer stands.

3. Consequences of pest establishment:

Economic Damage Potential: High (reasonably certain). These beetles in their natural range are often found attacking trees with other western pine beetles including mountain pine beetle and Ips spp. They are a primary component of the western bark beetle complex that has caused extensive tree mortality in California. They can also be the sole beetle attacking trees and causing mortality over large areas. Tree mortality contributes to timber loss, increased fuels and more extreme fire behavior Drought and warm conditions in recent years led to a western pine beetle epidemic killing large expanses of ponderosa pines in the central and southern Sierra Nevada in the Sierra, Sequoia, and Stanislaus National Forests, as well as parts of Yosemite and Kings Canyon National Parks (California Pest Council 2016). The USFS reported over 100 million trees were killed and up to 100% mortality in some stands. Western pine beetle epidemics were also notable in Pacific Coast states during droughts in 1920’s and 1930’s.

Western pine beetle is often found attacking live pines within fire perimeters.

Ecological Damage Potential: High (reasonably certain): Their presence in the Black Hills could add to large diameter tree mortality or reduce stocking on managed sites. Their populations could also build up in portions of trees attacked by mountain pine beetle increasing the amount of mortality seen during mountain pine beetle epidemics.

Perceived Damage Potential: High (reasonably certain). Western pine beetle is a major forest pest in California and has caused significant mortality in Oregon in the past.

4. Pest Impact Potential: High

5. Management Options. Once established management strategies would be similar to those used for mountain pine beetle.

California Fivespined Ips

1. Probability of pest establishment: High (reasonably certain). Ponderosa pine is a preferred host and abundant in the Black Hills region.

2. Spread potential: High (reasonably certain). This insect is common in California and has been expanding its range northward in the Pacific Northwest. Tree killing is being reported in Washington state and colder drier sites in Oregon than previously observed. Damage has been reported in managed stands in the eastern Columbia River Gorge in Washington and in the Willamette Valley ponderosa pine stands in Oregon.

3. Consequences of pest establishment:

Economic Damage Potential: Moderate (reasonably certain). California fivespined ips behaves like others in the Ips genus. It can flare up and cause pockets of mortality in ponderosa pine stands during droughts and it can build up in logging slash and attack standing trees. In managed areas it could reduce regeneration stocking. The Black Hills is currently seeing high levels of mature trees killed by native ips. California fivespined ips could contribute to increased top-kill and mortality to drought stressed trees or in regeneration where thinning treatments provide abundant slash breeding material.

Ecological Damage Potential: Moderate (reasonably certain). It is not known if the introduction of a new ips species into the Black Hills ecosystem will compete with or cause added tree losses to the ponderosa pine forest. In warmer drier years it could contribute to increased tree mortality.

Perceived Damage Potential: Moderate (reasonably certain).

4. Pest Impact Potential: Moderate

5. Management Options. Proper slash management and timing of thinning is important in managing this beetle, similar to management for other Ips species.