I am alerting you to two publications about our “favorite” tree-killing pathogen, Phytopthora ramorum (sudden oak death).
SOD-infected rhododendron in a nursery in Indiana; photo by Indiana Department of Natural Resources
The Role of Nurseries in Spreading SOD
The first article informs the general public and raises important questions: “The Diseased Rhododendrons That Triggered a Federal Plant Hunt” by Ellie Shechet in The New Republic.
Ellie reviews the 2019 episode in which P. ramorum-infected rhododendron plants were shipped to retailers in the East and Midwest. Her article is based on interviews with state plant health and APHIS officials, several scientists and advocates (including me), and the executive director of the Oregon Association of Nurseries (OAN). Ellie notes that infected plants were found at more than 100 locations across 16 states.
Ellie notes that despite the risk to native plants in the eastern deciduous forest and the financial cost of implementing control actions (14 million plants were inspected in Washington State alone), plants have a “green” reputation; they are not recognized as potentially causing environmental harm.
The politics of the situation also are reviewed. She writes that the OAN representative has testified that he helped write the more relaxed regulatory approach that APHIS adopted by “federal order” in 2014 and formalized in changes to the regulations in 2019. APHIS denies this. [The article does not include the information that during this period, state regulatory officials detected P. ramorum-infected plants in between four and ten Oregon nurseries each year.] Ellie notes that individual consumers buying plants have few tools to try to ensure that plants they buy are not infected by SOD or other pathogens.
The fact is that the climate in the coastal areas of California, Oregon, Washington, and British Columbia is conducive to SOD, so the risk of diseased plants being produced there and sold is constant. The current APHIS regulations do not adequately address this, in my view!
Science: High Risk of Phytophthora Introductions from Southeast Asia
The second article reports results of intense scientific effort: Thomas Jung, Joan Webber, Clive Brasier, and other European plant pathologists report more completely on searches for P. ramorum and other Phytophthora species in East Asia. See the full citation at the end of this blog. [I blogged about their preliminary report a little over a year ago.] Jung et al. conclude that P. ramorum probably originates from the laurosilva forests growing in an arc from eastern Myanmar, across northern Laos, Vietnam, and southwestern China (Yunnan) to Shikoku & Kyushu islands in southwest Japan. The article notes that two other Phytophtoras – P. lateralis (cause of fatal disease on Port-Orford cedar) and P. foliorum – appear to be from the same area. Field science by this team has found 38 previously unknown Phytophthora species in these same forests – and expect that more are present.
Clive Brasier in Vietnam; UK Forestry Research
They warn that the lack of information about potential pathogens in many developing countries presents a high risk of introduction to naïve environments through burgeoning horticultural trade – especially since the World Trade Organization requires that a species be named and identified as posing a specific threat before phytosanitary regulations can be applied. [I addressed the issue of international phytosanitary rules in Fading Forests II; see the link at the end of the blog.]
Other Pathogen Risks from the Region
Phytophthoras transported on imported plants are not the only pathogens that could come from Asia. The vectors and associated pathogens causing laurel wilt disease across the Southeast and Fusariumdisease in California are believed also to originate in the same region of Asia. Unlike the Phytophthoras, which are transported primarily through the trade in plants for planting, these fungi travel with the vector beetles in wood packaging material. U.S. imports of goods from Asia – often packaged in wooden crates or pallets – have skyrocketed since July 2020. The ports of Los Angeles-Long Beach, which receive 50% of U.S. imports from Asia, handled 6.3 million TEU (twenty-foot equivalent containers) from Asia during the period July 2020 through February 2021. The average of close to 800,000 TEU per month for eight consecutive months is unprecedented. Other ports also saw increased import volumes from Asia during this period. [I discussed these shifts in my blog in January.] Imports from Asia in 2020 accounted for 67.4% of total US imports from the world. Imports from China specifically accounted for 42.1% of total US imports. [Data on import volumes is from several reports posted by the Journal of Commerce at its website: https://www.joc.com/maritime-news/]
SOURCE
Jung, T.; Horta Jung, M.; Webber, J.F.; Kageyama, K.; Hieno, A.; Masuya, H.; Uematsu, S.; Pérez-Sierra, A.; Harris, A.R.; Forster, J.; et al.. The Destructive Tree Pathogen Phytophthora ramorum Originates from the Laurosilva Forests of East Asia. J. Fungi 2021, 7, 226. https://doi.org/10.3390/ open access!
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
Two USDA agencies lead efforts to protect U.S. wildland, rural, and urban forests from non-native insects and disease-causing pathogens:
USDA Animal and Plant Health Inspection Service (APHIS) has legal responsibility for preventing introduction of tree-killing pests, detecting newly introduced pests, and initiating eradication and containment programs intended to minimize the damage they cause.
USDA Forest Service (USFS)
Forest Health Management (FHM) program assists partner agencies to counter pests where they are first found – usually near cities – and when they spread. This work falls primarily to the Cooperative component of Forest Health Management program. The Federal lands component helps the USFS, National Park Service, and other federal agencies counter pests that have spread to more rural/wildland areas.
Research and Development (R&D) program supports research into pest-host relationships, introduction & spread pathways, management strategies (including biocontrol) and host resistance breeding
Since 2010, several new tree-killing pests have been detected in the US, including polyphagous and Kuroshio shot hole borers, spotted lanternfly, two rapid ʻōhiʻa death pathogens, and Mediterranean oak beetle. Over the same period. the Asian longhorned beetle has been detected in two new states – Ohio and South Carolina; the emerald ash borer expanded its range from 14 to 35 states; laurel wilt disease spread from five states to 11; a second strain of the sudden oak death fungus appeared in Oregon and California forests; and whitebark pine has been proposed by the US Fish and Wildlife Service for listing as Threatened under the Endangered Species Act. (I have blogged often about policy failures that have contributed to these introductions; today I am focused on agencies’ ability to respond.)
Funding agencies’ essential programs has fallen behind these calamities. APHIS funding has been steady or has risen slowly – at least not dropping – but not enough to deal with the growing threat.
Meanwhile, the key USFS programs have been cut by half or more. In 2010, USFS FHP and Research, together, allocated $32 million to efforts to understand and manage a dozen introduced pests: Asian longhorned beetle, emerald ash borer, sudden oak death, hemlock woolly adelgid, goldspotted oak borer, laurel wilt, thousand cankers disease, European gypsy moth, Port-Orford cedar root disease, Sirex woodwasp, and white pine blister rust (especially on whitebark pine). By 2021, this total had fallen to about $10 million. There was no indication that any USFS R&D funding has been allocated to recently detected, highly damaging pests, i.e., rapid ʻōhiʻa death, the polyphagous and Kuroshio shot hole borers, Mediterranean oak beetle, or beech leaf disease. USFS FHP has funded work on some of these pests through its “emerging pest” fund – but that fund is limited to $500,000 for the entire country.
At present, more than 228 tree species growing in the “lower 48” states are infested by an exotic pest. The 15 most damaging of the introduced species threaten 41.1% of the total live forest biomass in the 48 conterminous states. Additional trees on the Hawaiian and other Pacific islands are also being killed by non-native insects and pathogens. Non-native forest pests have caused a 5% increase in total mortality by tree volume nation-wide. The greatest increases in mortality rates have been a four-fold increase for redbay; and a three-fold increase each for ash, beech, and hemlock.
Introductions of tree-killing pests occur because we import things! The highly damaging wood-borers can arrive in crates, pallets, and other forms of packaging made of wood. Other pests – especially plant diseases – come here on imported plants. Gypsy moth and spotted lanternfly egg masses can be attached to virtually any hard surface, e.g., steel slabs, vehicles, stone, containers, or ship superstructures.
Imports from Asia pose a particularly high risk – illustrated by the Asian longhorned beetle, emerald ash borer, polyphagous and Kuroshio shot hole borers, sudden oak death, and spotted lanternfly.
U.S. imports from Asia rose almost a third between 2019 and 2020. No part of the country is safe. While nearly half of imports from Asia enter via Los Angeles/Long Beach, California, another 21% entered via New York – New Jersey and Savannah. Other ports in the “Top 10” were the Northwest Seaport Alliance of Seattle and Tacoma, Oakland, Norfolk, Houston, Charleston, Baltimore, and Mobile.
Pests don’t stay in the cities where they first arrive. Instead, they proliferate and spread to other vulnerable trees – often assisted by people moving firewood, plants or household goods. For example, less than 20 years after their first detections, the emerald ash borer has spread to 35 states, the redbay ambrosia beetle to 11.
[For more information, read my earlier blogs posted here or species-specific descriptions here.]
Please contact your Representative and Senators and urge them to push for increased funding for key programs managed by these two agencies. I describe funding needs below. I list members of the appropriate Congressional subcommittees at the end of this blog.
APHIS headquarters
USDA APHIS programs (all included under “Plant Protection and Quarantine”)
APHIS Program
FY 2020 (millions)
FY 2021 (millions)
FY 2022 ask
Tree & Wood Pest
$60.000
$60.456
$70 million
Specialty Crops
$192.000
$196.553
$200 million
Pest Detection
$27.446
$27.733
$30 million
Methods Development
$20.686
$20.844
$25 million
APHIS’ “Tree & Wood Pests” account has traditionally supported eradication and control efforts targeting only three insects: the Asian longhorned beetle (ALB), emerald ash borer (EAB), and gypsy moth. The program to eradicate the ALB has received about two-thirds of the funds — $40 million. There is encouraging progress in Massachusetts, New York, and Ohio. Clearly, this program must be maintained until final success is achieved. Plus the program must now counter the Charleston, South Carolina, outbreak, where more than 4,000 infested trees have been detected in an area of 58 square miles. (See my blog here, which describes the difficult conditions arising from wetlands in South Carolina.)
APHIS has terminated its emerald ash borer regulatory program, which had previously been funded at about $7 million per year. (See my blog). APHIS has said it will now focus on production and release of biocontrol agents, although it has not indicated the funding level. It is probable that EAB will now spread more rapidly to the mountain and Pacific Coast states, threatening both riparian woodlands and urban forests.
APHIS’ “Specialty Crops” program funds APHIS’ regulation of nursery operations to prevent spread of the sudden oak death pathogen. APHIS must improve that program to avoid a repetition of the 2019 incident, in which plants infected by the SOD pathogen were shipped to 14 states.
This budget line also supports efforts to manage the spotted lanternfly, which has spread from Pennsylvania to seven other mid-Atlantic states.
The “Pest Detection” budget line supports the collaborative state –federal program that detects newly introduced pests. Successful eradication and containment programs depend on early detection.
The “Methods Development” program assists APHIS in developing detection and eradication tools essential for an effective response to new pests.
USDA Forest Service
USFS PROGRAM
FY20
FY21
FY 22 ask
FHP Coop Lands
$32 M
$30.747M
$51 million (to cover both program work & personnel costs)
FHP Federal lands
$19 M
$15.485M
$25 million (ditto)
Research & Develop
$305 million
$258.7 million; of which about $3.6 million allocated to invasive species
$320 million; seek report language specifying $5 million for invasive species
The Mission of the USDA Forest Service is “To sustain the health, diversity, and productivity of the Nation’s forests and grasslands to meet the needs of present and future generations.” To achieve this mission, the Forest Service needs adequate funding to address the difficult challenge of containing the spread of introduced pests, protecting host tree species from mortality caused by those pests, and restoring decimated tree species to the forest. Meeting this challenge requires gaining scientific understanding of the pest’s and host’s biology and what motivates people to avoid activities that facilitate pests’ spread (e.g., transporting firewood that might harbor wood-boring insects).
Given the hundreds of damaging non-native pests, the Forest Service must set priorities. One attempt to do so is “Project CAPTURE” (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation). Priority species for forests on the continent are listed below. A separate study is under way for forests in Hawai`i, Puerto Rico, and U.S. Virgin Islands.
Florida torreya (Torreya taxifolia)
American chestnut (Castanea dentata)
Allegheny chinquapin (C. pumila)
Ozark chinquapin (C. pumila var. ozarkensis)
redbay (Persea borbonia)
Carolina ash (Fraxinus caroliniana)
pumpkin ash (F. profunda)
Carolina hemlock (Tsuga caroliniana)
Port-Orford cedar (Chamaecyparis lawsoniana)
tanoak (Notholithocarpus densiflorus)
butternut (Juglans cinerea)
eastern hemlock (Tsuga canadensis)
white ash (Fraxinus americana)
black ash (F. nigra)
green ash (F. pennsylvanica).
These 15 priority species should be the focus of both comprehensive gene conservation programs and tree breeding and restoration programs. Unfortunately, USFS programs do not reflect this recommendation.
Forest Health and Management Programs (FHM)
Despite severe cuts (see above), FHM has continued its commitment to projects addressing Port-Orford-cedar root disease, threats to whitebark pine, and thousand cankers disease; plus it is support for managing “lingering” ash which appear to survive EAB attack. However, I am concerned about past reductions in programs targetting laurel wilt and sudden oak death. And as I noted above, several highly-damaging pests lack a “program” at all. I applaud establishment of an “emerging pest” line. However, competition will be fierce for the $500,000 – pitting the invasive shot hole borers in California against the coconut rhinoceros beetle and rapid ‘ōhi‘a death in Hawai`i, against beech leaf disease in Ohio to Massachusetts.
And where is federal leadership on managing continued spread of the emerald ash borer, now that the USDA APHIS has terminated its regulatory program?
USDA Forest Service Forest and Rangeland Research Program
Effective programs to prevent, suppress, and eradicate non-native pests depend on understanding of the pest-host relationship gained through research. In recent years, about 1.5% of the USFS Research budget has been allocated to the non-native pests listed above. Past reductions have hit programs targetting hemlock woolly adelgid, white pine blister rust, sudden oak death, and the Sirex woodwasp. Programs targetting several other high-impact pests, including the Asian longhorned beetle, emerald ash borer, goldspotted oak borer, thousand cankers disease, and laurel wilt have been funded at a steady rate. I could find no documentation of USDA Forest Service research into beech leaf disease, rapid ʻōhiʻa death, or other pests currently killing trees.
Members of Key Congressional Committees
Note that some Representatives or Senators are members of subcommittees that fund both APHIS and the USFS. It is especially important that they hear from their constituents!
APHIS is funded through the Agriculture appropriations bill. Members of the House Subcommittee on Agriculture and Rural Development:
Sanford Bishop Jr., Chairman GA
Chellie Pingree ME
Mark Pocan WI
Lauren Underwood IL
Barbara Lee CA
Betty McCollum MN
Debbie Wasserman Schultz FL
Henry Cuellar TX
Grace Meng NY
Jeff Fortenberry, Ranking Member NE
Robert Aderholt AL
Andy Harris MD
David Valadao CA
John Moolenaar MI
Dan Newhouse WA
Members of the Senate Subcommittee on Agriculture and Rural Development:
Tammy Baldwin, Chair WI
John Merkley OR
Dianne Feinstein CA
Jon Tester MT
Patrick Leahy VT
Brian Schatz HI
Martin Heinrich NM
Ranking Republican John Hoeven ND
Mitch McConnell KY
Susan Collins ME
Roy Blunt MO
Jerry Moran KS
Cindy Hyde-Smith MS
Mike Braun IN
The USFS is funded through the Interior appropriations bill. Members of the House Subcommittee on Interior and Related Agencies: add states
Chellie Pingree, Chair ME
Betty McCollum MN
Derek Kilmer WA
Josh Harder CA
Susie Lee NV
Marcy Kaptur OH
Matt Cartwright PA
David Joyce, Ranking Member NC
Mike Simpson ID
Chris Stewart UT
Mark Amodei NV
Members of the Senate Subcommittee on Interior and Related Agencies:
Jeff Merkley, chair OR
Dianne Feinstein CA
Patrick Leahy VT
Jack Reed RI
Jon Tester MT
Chris van Hollen MD
Martin Heinrich NM
Ranking Rep. Lisa Murkowski AK
Roy Blunt MO
Mitch McConnell KY
Shelly Moore Capito WV
Cindy Hyde-Smith MS
Bill Hagerty TN
Marco Rubio FL
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
map showing spread of beech scale, which facilitates beech bark disease
I recently participated in the 2021 annual meeting of the Northeast Forest Pest Council (virtual, of course). Speakers – most of them from state forestry agencies, but including students – presented a disturbing picture. Numerous established insects and diseases continue to spread. In some cases, they are resurging after weather-caused slow-downs. There are also a few bright spots.
The Alarming
To me the most alarming situation is that for American beech – because all three threats continue to expand.
Beech bark disease Since 2000, BBD has spread across southern Quebec into Ontario, Michigan, and Wisconsin; the Blue Ridge in Virginia; and central New Jersey.
Beech leaf disease Originally discovered near Cleveland in 2012, BLD has been spreading, primarily eastward.
BLD was detected for the first time in Massachusetts, in Plymouth and Bristol counties (on the coast North of Cape Cod). It might also be in Worcester. Both American and European beech trees of all sizes are affected; some of the largest are “on the verge” of death. (Felicia Hubacz)
The first detections in New Jersey are in Bergen and Essex counties – bordering southern New York. Both detections were by members of the public. Rosa Yoo says there is confusion about which state agency has the lead, so no official notices have been published (although the detection is recorded on the map). She hopes to establish long-term monitoring plots.
West Virginia now says that BLD is present in Tomlinson Run State Park in Hancock County. Kristen Carrington plans to focus detection efforts on the state’s norther panhandle which rises along the Pennsylvania border. She has established seven long-term monitoring plots.
Meanwhile, states where BLD was detected earlier continue to add new counties to the list of those infested. In New York, five new counties have been recorded. All the New York State finds have been on public lands, so the map doesn’t present the full picture (Carlson). In Connecticut, the disease is in all coastal counties and is more scattered in inland areas. Connecticut has set up some long-term monitoring plots. (Stafford)
New York is also trying to identify insect species associated with beech trees and beech litter – as a first step in trying to determine whether any vector the nematode that is thought to cause the disease. I suggest that it is also useful to understand which arthropod species might be at risk as beech decline. Don’t folks often lament the lack of this information for chestnut? Aren’t scientists praised for compiling initial lists for insects associated with ash?
Beech leaf mining weevil According to Jeff Ogden of the Nova Scotia Department of Lands and Forestry, this weevil has defoliated trees on 5987 hectares. First detected near Halifax in 2012, the weevil is now found throughout Nova Scotia. Some trees near Halifax have died. Ogden believes the weevil could be spread on movement of logs with bark and leaf litter. Camping is very popular in Nova Scotia, so the firewood risk appears real.
Also alarming is the resurgence of hemlock woolly adelgid across the region. HWA had been suppressed for a few years by harsh winters, but that reprieve is over. HWA is in 52 of 55 West Virginia counties (Kristen Carrington). Newly detected outbreaks are found across Pennsylvania and in the Adirondacks of New York. HWA continues to spread north – slowly – in New Hampshire and Vermont. In Nova Scotia, the outbreak detected in 2018 is spreading slowly to the West (Jeff Ogden).
All states are releasing a variety of biocontrol agents, often Laricobius nigrinus but also L. osakensis. Various agents have been released for decades — for example, Connecticut has released more than 125,000 agents over more than 20 years. I do hope the two Laricobius beetles prove to be more effective in controlling the agelgid.
Several states note that elongate hemlock scale (Fiorinia externa) is now at least as damaging as the adelgid.
Pennsylvania is growing hemlocks for restoration purposes; New Jersey has begun a similar program. See my earlier blog about efforts to breed hemlocks resistant to the adelgid, available here.
Spotted lanternfly is now established in nine states — from Ohio and West Virginia to Connecticut. It continues to spread. In the longer-established infestation areas of southeastern Pennsylvania, black walnut has been severely damaged by early instar larvae. In New Jersey, eight counties are under quarantine, but the insect has been detected much more broadly. The newest state is Connecticut, which found populations in several counties and is drafting quarantine regulations. Massachusetts, Maine, and Vermont have found some egg masses or evidence of infestation on goods entering from Pennsylvania, but not yet an established population.
The Not So Alarming — but Still Concerning
Asian Longhorned BeetleMassachusetts is consistently finding fewer trees infested by the ALB. In 2020, they found only one! It was isolated in the middle of a golf course. Intensive surveys and trapping in the vicinity found no other infested tree.
This is great news! However, I worry that resources will be withdrawn too soon – especially with APHIS’ need to fund an eradication program for the same pest in a swampy forest area in South Carolina where it will be difficult to work. Already Massachusetts reported that it has fewer traps and staff, and some difficulties accessing the lure.
Early Detection Efforts
New Jersey and West Virginia have carried out surveys of sassafras stands for the redbay ambrosia beetle (also here). West Virginia is also surveying for Phytophthora ramorum (the sudden oak death pathogen) and walnut twig beetle (vector of thousand cankers disease). Funding for surveys of the former probably came from USFS Forest Health Protection; for the latter, from APHIS. I applaud these “early detection” efforts.
Too Late for “Early Detection” but Getting Welcome the Attention
New Hampshire noted rising concern about Jumping worms. The state has received 48 complaints since 2017; 43 of these were in 2020. This led to a spirited discussion about invasive worms’ impacts. Don Eggen noted that concern focuses on soils in unglaciated regions. Non-native worms can destroy the duff layer. Most of the research has been carried out in the Midwest. See my earlier blogs about invasive earthworms here.
Tim Tomon reported that the USFS Morgantown WV research office has sampled the Allegheny NF. They have found other invasive earthworms but not jumping worms. Rosa Yoo of New Jersey alerted participants to the jumping worm research and management group – JWORM
Other Updates
Beech leaf disease
The USDA Forest Service has published a Pest Alert on BLD. Google it now. When a url becomes available I will update this notice. The flyer includes contact information for a site that provides both detection training and a place to record your finds.
Sudden Oak Death
The EU1 strain was detected in forest trees in Del Norte County, California in autumn 2020. This detection was both the first officially confirmed detection of P. ramorum in Del Norte County and the first detection of the EU1 strain in forest trees in California. The source is unclear. The nearest infestation is 12 miles away, along the Winchuk River in Curry County, OR; those trees are infected with the NA1 strain. The nearest known EU1 infestation is about 35 miles away. The site of the California EU1 infestation has minimal California bay laurel (Umbellularia californica). This detection has led to designation of Del Norte County as officially infested; it becomes the 16th California county so designated. [Information from the California Oak Mortality Task Force newsletter for December 2020, available here.]
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
Rep. Peter Welch of Vermont has reintroduced his bill to improve programs intended to prevent introduction of non-native forest pests and enhance efforts to reduce their impacts. The latter provisions include support for breeding trees resistant (or tolerant) to the pest. I hope H.R. 1389 will be adopted – then spur new efforts to conserve and restore forest trees! Please follow my suggestion below.
The Invasive Species Prevention and Forest Restoration Act H.R. 1389 is co-sponsored by Reps. Brian Fitzpatrick (PA), Annie Kuster & Chris Pappas (NH), and Elise Stefanik (NY).
“Invasive species are devastating to forests which are a central part of Vermont’s economy and our way of life. This bill will fund efforts to revitalize damaged forests and highlight the need for making this a priority within the federal government.”
Major provisions of H.R. 1389:
Expands USDA APHIS’ access to emergency funding to combat invasive species when existing federal funds are insufficient and broadens the range of actives that these funds can support.
Establishes a grant program to support institutions focused on researching methods to restore native tree species that have been severely damaged by invasive pests.
Authorizes funding to implement promising research findings on how to protect native tree species.
Mandates a study to identify actions needed to overcome the lack of centralization and prioritization of non-native insect and pathogen research and response within the federal government, and develop national strategies for saving tree species.
As I have described in earlier blogs, the measures adopted by federal and state governments to prevent non-native pathogen and insect pest introductions – and the funding to support this work – have been insufficient to meet the growing challenges. In just the past decade, several new tree-killing pests have been detected: polyphagous and Kuroshio shot hole borers, spotted lanternfly, two rapid ʻōhiʻa death pathogens, Mediterranean oak beetle, velvet longhorned beetle. Over the same period, the Asian longhorned beetle has been detected in Ohio and South Carolina; the emerald ash borer expanded its range from 14 to 35 states; the redbay ambrosia beetle and its associated fungus spread from five states to 11; a second strain of the sudden oak death fungus appeared in Oregon forests; and whitebark pine has been proposed by the US Fish and Wildlife Service for listing as Threatened under the Endangered Species Act.
During this same period, funding for the USDA Forest Service Forest Health Protection program has been cut by about 50%; funding for USFS Research projects targetting 10 high-profile non-native pests has been cut by about 70%.
One reason for this disconnect between need and resources is that the non-native tree pest problem is largely out of sight and therefore does not lend itself to the long-term public attention needed to remediate the threats. It is up to us to raise the political profile of these issues.
On the positive side, the passage of time has brought forth new solutions, a deeper understanding of the genetics of plants and animals, new measures for igniting public awareness and invasive identification, new technologies and strategies for helping trees adapt, and a recognition of what resources and organization it will take to mount a proper solution to the problem.
“Project CAPTURE” (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation) has proposed priority species for enhanced conservation efforts. Top priorities in the continental states are listed below. A separate study is under way for forests in Hawai`i, Puerto Rico, and U.S. Virgin Islands.
dead redbay on Jekyll Island, Georgia
Florida torreya (Torreya taxifolia)
American chestnut (Castanea dentata)
Allegheny chinquapin (C. pumila)
Ozark chinquapin (C. pumila var. ozarkensis)
redbay (Persea borbonia)
Carolina ash (Fraxinus caroliniana)
pumpkin ash (F. profunda)
Carolina hemlock (Tsuga caroliniana)
Port-Orford cedar (Chamaecyparis lawsoniana)
tanoak (Notholithocarpus densiflorus)
butternut (Juglans cinerea)
eastern hemlock (Tsuga canadensis)
white ash (Fraxinus americana)
black ash (F. nigra)
green ash (F. pennsylvanica).
For a brief explanation of Project CAPTURE, see my earlier blog here. For an in-depth description of the Project CAPTURE process and criteria for setting priorities, read Potter, K.M., M.E. Escanferla, R.M. Jetton, and G. Man. 2019. Important Insect and Disease Threats to United States Tree Species and Geographic Patterns of Their Potential Impacts. Forests 2019, 10. https://www.fs.usda.gov/treesearch/pubs/58290
Please ask your representative to co-sponsor H.R. 1389. Please ask your senators to sponsor a companion bill. For more information, contact Alex Piper at Alex.Piper@mail.house.gov or 202-306-6569 .
H.R. 1389 is endorsed by Vermont Woodlands Association, American Forest Foundation, Center for Invasive Species Prevention, the Reduce Risk from Invasive Species Coalition,, Entomological Society of America, and North American Invasive Species Management Association.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
Horton House on Jekyll Island, Georgia – when the redbays were still alive! photo by Faith Campbell
A recent USFS book on invasive species reports that at least 58 species of bark and ambrosia beetles have been established in the US. Recent studies highlight very different situations due to two invasive ambrosia beetles. Here are summaries of each.
1. Laurel Wilt: Unmitigated Disaster in Atlantic and Gulf Coastal Plains – and Possibly More Widely
The disease laurel wilt, caused by the pathogen Raffaelea lauricola and vectored primarily by the redbay ambrosia beetle (Xyleborus glabratus) presents a dire contrast. (For this section, see Olatinwo, Fraedrich & Mayfield. 2021; full reference at end of the blog.) In the nearly 20 years since its first detection near Savannah, Georgia in 2002, laurel wilt has spread across more than 100 counties and parishes in 11 states from North Carolina south through Florida, west to eastern Texas, and as far northward as Kentucky.
Laurel wilt has killed hundreds of millions of trees in the plant family Lauraceae. Approximately 13 Lauraceae species in eight genera (depending on taxonomic proclivities!) are indigenous to the U.S. Individual species’ vulnerability appears to depend largely on size; the beetle is attracted to vertical stems of a certain diameter. As a result, the native tree species redbay (Persea borbonia), swampbay (Persea borbonia var. pubescens or P. palustris), and more recently sassafras (Sassafras albidum) have experienced the most damaging attacks. Also heavily attacked has been the commercial avocado (Persea americana) which is native to Central America.
sassafras photo by David Moynihan
While redbay is widespread in a defined geographic area – a long the Atlantic and Gulf Coastal Plain from North Carolina to Texas, sassafras is subcontinental: it is found in 28 states, 53 ecoregions, and 69 forest types. Approximately 80% of sassafras in affected areas have been killed. In recent years, spread has proceeded by many “jumps” to disjunct areas where sassafras occurs in isolation from other hosts. At present, approximately 52% of the range of sassafras might experience winter temperatures sufficiently cold to cause significant mortality of the redbay ambrosia beetle. However, this temperature protection is likely to decline to about10% of sassafras’ range as a result of even modest climate change (a 1.4 °C increase in winter minimum temperatures).
The ecological impact of loss of redbay and sassafrass are not clear. Both are sources of wildlife food. The principal specialist on redbay is the Palamedes swallowtail butterfly (Papilio palamedes), which is also the primary pollinator of a rare plant, yellow-fringed orchid. The rapid loss of swampbay on tree islands in the Everglades could facilitate establishment of even more individuals of the already widespread invasive plant species Brazilian pepper (Schinus terebinthifolius) or Melaleuca quinquenervia.
Other U.S. native plant species in the Lauracea family are apparently partially protected by the small diameter of their stems, which the beetle doesn’t find acceptable. These include – in the Southeast — the federally listed pondberry (Lindera melissifolia), “species of interest” pondspice (Litsea aestivalis), bog spicebush (Lindera subcoriacea), pepperleaf sweetwood (Licaria trianda), lancewood (Ocotea coriacea), and love-vine (Cassytha filiformis). The common shrub spicebush (Lindera benzoin) might be protected by its possession oflower quantities of the primary host volatile attractant. On the other hand, the widespread Pacific state shrub California laurel or Oregon myrtle (Umbellularia californica) is considered highly vulnerable, should laurel wilt be moved there in wood, mulch, or nursery plants.
Laurel wilt poses an unknown threat to the many plant species in the Lauraceae in Central and South America (750 species), Australia (125 species), Madagascar (135 species), and the Macaronesian Islands off the coasts of Europe and Africa – the Azores, Canary Islands, and Madeira. The commercial spice bay laurel (Laurus nobilis) is native to the Mediterranean region (and planted elsewhere, including in the US). However, its small size, discontinuous distribution and isolation from other lauraceous host species might prevent development of a widespread epidemic.
The authors note the absence of effective measures to manage laurel wilt 20 years after its detection. They recommend restricting long-distance movement of infested wood, associated public awareness efforts, development and deployment of resistant hosts, silviculture (sanitation), targeted application of preventive chemical treatments for protecting high-value trees, and severing root grafts in avocado orchards and sassafras clones. They note that success will be dependent on sustained funding and a commitment to long-term area-wide implementation.
[As I noted in past blogs about APHIS deregulating the emerald ash borer, it is now up to the states to regulate movement of firewood. The lead will continue to be the non-governmental “Don‘t Move Firewood” campaign. The message will continue to encourage the public to buy firewood where they burn it and to refrain from moving firewood from areas that are under Federal quarantine for other pests of firewood (e.g., Asian longhorned beetle). This campaign and the new National Plant Board guidelines stress that firewood is a high-risk pathway for many pests of national or regional concern; they do not focus on any particular species. Leigh Greenwood, director of Don’t Move Firewood, thinks this is a good approach.]
Mayfield adds that the spread northwards on sassafras means that state diagnostic pathology labs should familiarize themselves with protocols for isolating the laurel wilt pathogen.
As to developing resistant varieties of redbay, I note that Potter et al. 2019 ranked redbay as fifth species highest in priority for genetic conservation and restoration breeding efforts. However, it is my impression that few federal resources have been allocated to such an effort on behalf of redbay.
2. Ambrosia beetles in California
At least 22 of the recently-established ambrosia and bark beetles are in California. Heavily urbanized southern California appears to be particularly vulnerable to such introductions. The proximity of ship traffic and associated cargo, as well as the great diversity of potential hosts in the area’s urban forests, are likely to blame.
Two such pests are the polyphagous (PSHB) and Kuroshio (KSHB) shot hole borers [collectively, invasive shot hole borers (ISHB)]. John Boland has studied the KSHB outbreak in the Tijuana River estuary intensively since 2015. Two recent studies – 2019 and 2021– demonstrate the importance of ecological and tree-related factors in determining the severity of attack by this ambrosia beetle. See references at the end of the blog.
The most susceptible site is wet and nutrient enriched (in the case of the Tijuana River, due to pollution).
The most susceptible trees are young, fast growing, and have thin bark (allowing KSHB access) and wood of low density and high moisture content (providing ideal conditions for KSHB and associated fungi).
willows killed by KSHB in Tijuana River estuary; photo by John Boland
As Boland has noted, all of these conditions occurred in the “wet” forests close to perpetual streams in the Tijuana River delta in 2015. These factors led to dramatic levels of mortality, which have not been equaled in other southern California deltas. In the five years from 2015 to 2020, the beetle/fungus complex infested an estimate 350,000 willows and killed an estimated 123,000 in a boom-and-bust cycle. Since 2016, the trees in the Tijuana River estuary have regrown to almost pre-infestation dimensions. (Boland is not certain why these new, fast-growing trees have not been attacked by the KSHB that remain in the area. He suggests that a local pathogen, parasite, parasitoid or predator is keeping the KSHB in check – although this has not been verified.)
Willows near the main river channel (“Wet Forest” units) cumulatively had a fatality rate of 39%. Strikingly, more distant “Dry Forest” units had a combined fatality rate of only 9%.
The 2019 study linked the higher rates of infestation, damage, and mortality that occurred in trees near the main river channel to the presence of year-round water that was often enriched by a heavy load of sewage. The trees respond by growing rapidly, resulting in thinner bark and less dense wood. The KSHB attacked in much higher numbers, impeding water transport and weakening the trees’ structure so that they were more easily broken during windstorms.
The 2021 study provided further detail. By comparing bark samples cut from 27 infested trees at the height of the infestation, in 2016 – 17, Boland and Woodward demonstrated thicker bark on the “Dry Forest” trees protected the trees by limiting the density of KSHB entry points. The fewer holes reduced internal structural damage to the trees, which allowed them to survive. Boland notes that the protection might arise from either the bark thickness itself, or higher quantities of protective chemicals.
Repercussions
The results suggest that a KSHB individual actively searches for a suitable tree and then searches for the thinnest bark on that tree in which to drill its hole.
Trees can recover from KSHB attack, indicating that the fungal symbionts are only moderately pathogenic at worst.
The ISHB are likely to cause much less damage than indicated by the one early model developed before these factors were understood. We need new models for ISHB spread and impact that incorporate these factors of site characteristics and host tree condition.
Boland J.M. and D.L. Woodward. 2021. Thick bark can protect trees from a severe ambrosia beetle attack. PeerJ 9:e10755 https://peerj.com/articles/10755/
Olatinwo, R.O., S.W. Fraedrich & A.E. Mayfield III. 2021. Forests 2021, 12, 181. Laurel Wilt: Current and Potential Impacts and Possibilities for Prevention and Management
Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S. 2019. Prioritizing the conservation needs of US tree spp: Evaluating vulnerability to forest P&P threats, Global Ecology and Conservation (2019), doi: https://doi.org/10.1016/ j.gecco.2019.e00622.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
spotted lanternfly; photograph by Holly Ragusa, Pennsylvania Department of Agriculture
Since Fiscal Year (FY)2009, APHIS has had access to a program that has permanent funding, not subject to the vagaries of annual budgeting and appropriations. The Plant Pest and Disease Management and Disaster Prevention Program established by 7 U.S.C. Section 7721. The program was initially funded at $12 million for FY2009; $45 million in FY2010; $62.5 million in 2014-2017; and $75 million since FY2018.
Funds are provided under a competitive grants program to universities, states, Federal agencies, nongovernmental organizations, non-profits, and Tribal organizations “to conduct critical projects that keep U.S. crops, nurseries, and forests healthy, boost the marketability of agricultural products within the country and abroad, and help us do right and feed everyone.” [USDA press release “USDA Provides $66 Million in Fiscal Year 2019 to Protect Agriculture and Natural Resources from Plant Pests and Diseases” February 15, 2019]
By my calculation, total funding of tree pests projects during the period Fiscal Year (FY09) through FY20 was about $94 million. This represented 15.6% of nearly $600 million in total funding under the program during this period.
In the initial years, forest pest projects received about 10-12% of total funds. In later years, the proportion has been higher – e.g., 30% in FY19, 13.8% in FY20. The early years were dominated by management of the sudden oak death pathogen (SOD), Phytophthora ramorum. In FY09, SOD projects receive $7.5 million, or 8% of all tree pest funding. This funding helped set up the National Ornamental Nursery study center (NORS-DUC); later years paid for research projects on SOD management issues and nursery surveys.
In the most recent years, funding has been dominated by detection, management, and research on spotted lanternfly – which is not primarily a forest pest. Thus, in FY 19, 56.8% ($10,339,126) of $18,195,000 allocated to tree pests; in FY20, 30% ($2,606,094) of the $8,705,920 allocated to all tree pests.
The FY2019 program also provided $1,107,965 in 14 states and nationally for P. ramorum survey, diagnostics, mitigation, probability modeling, genetic analysis, and outreach (USDA press release 2019). This was appropriate considering the shipment of SOD-infected plants to nurseries in 18 states in spring 2019.
Current Year Funding
APHIS has released the list of projects funded under the Plant Protection Act Section 7721 in FY2021. Link to website APHIS funded 354 projects in 49 states, Guam, Puerto Rico and the District of Columbia, at a total cost of $63.225 million. APHIS is retaining ~ $14 million to allow responses to pest and plant health emergencies. Total funding for forest pests – by my calculation – was $8,715,046 (13.7% of the total).
My analysis finds that in FY21, 13 states had no funded projects that applied to tree pests: Arizona, Colorado, District of Columbia, Guam, Hawaii, Idaho, Nebraska, New Jersey, New Mexico, North Dakota, Rhode Island, South Dakota, and Utah.
Most commonly funded projects:
Surveys and other efforts addressing wood borers: 37 projects, including
Thousand cankers disease: 4 (all surveys)
Emerald ash borer: 6 projects (surveys and management, including biocontrol)
Asian longhorned beetle: 3, of which 2 are outreach
Laurel wilt disease: 1 project
Detection tools for wood-borers, including citrus longhorned beetle, Sirexnoctilio, Agrilus biguttatus, and Australian Cerambycids
Phytophthora ramorum: 20 projects, primarily nursery surveys but including a few management projects. The projects were in 18 states.
Surveys for Asian defoliating moths in the Lymantra genus: 15 projects
Surveys and control efforts targetting spotted lanternfly: 13 projects in 6 states. These included research conducted by the APHIS Otis laboratory in Massachusetts. The grants totaled $2,788,010, or 32% of total forest pest funding.
APHIS funded 16 outreach projects (there is some overlap with above), including three specifically mentioning firewood. The latter included principal funding for the “Don’t Move firewood” national campaign.
Other projects that I find interesting:
2 projects targetting hemlock woolly adelgid
1 targetting red palm weevil
4 projects targetting Asian giant hornet in Washington and Oregon and the APHIS Otis laboratory. California has a project relating to a wider range of hornets that was also funded in FY20.
Biocontrol of several invasive plant species in Florida – Australian pine/Casuarina, Brazilian pepper, and Ailanthus
Harrisia cactus attacked by the mealybug; photo by Yorelyz Rodríguez-Reyes
As readers of this blog know, I also care deeply about threats to our native cacti – especially flat-padded Opuntia and tubular cacti endemic to Puerto Rico. Over the 13 years of program, funded following projects for cacti:
FY11 $244,368 for efforts to develop sterile insect methodology to control cactus moth
FY17 develop biocontrol for Harissia cactus mealybug $210,000
FY 21 cactus moth biocontrol $175,659 and $352,236 for Harrisia cactus mealybug biocontrol
Clearly, having access to $75 million that is not subject to the limits imposed by Administration budget priorities or Congressional appropriations has allowed considerable freedom. The fund has allowed APHIS to support work on pests that have not been designated “quarantine pests,” e.g., walnut canker disease of walnut, the polyphagous and Kuroshio shot hole borers, hemlock woolly adelgid, and the cactus pests. The program also funded many projects targetting the spotted lanternfly (SLF) – both before and after the lanternfly became a formal APHIS program (which occurred after it was detected outside Pennsylvania). Now that SLF has been found in several states, funding has partially shifted to appropriated funds. The FY21 appropriation included an additional $4 million for management of SLF; this was incorporated in the “specialty crops” line item.
So far, there has been no funding for beech leaf disease through this program; I don’t know whether any of the people working on this disease had applied.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
In January 2021, the California Department of Food and Agriculture announced the pest rating for Phytophthora occultans, one of two species of Phytophthora it was reviewing. (Once at the website, click on “comment” – next to name Heather Sheck.)
Five people or organizations submitted comments. The most comprehensive comments were submitted by Elizabeth Bernhardt, Ph. D. and Tedmund Swiecki Ph.D. of Phytosphere Research. Another scientist was Tyler Bourret, who had been the first to detect P. occultans in California when working as a student in 2015-16. The third scientist was Jennifer Parke, a plant pathologist at Oregon State University who has worked with Phytophthora species in agriculture and wildland settings for 36 years. Additional comments were submitted by the Phytophthoras in Native Habitats Work Group and me.
All commenters raised some issues. First was the lack of information on the true distribution of P. occultans in California. CDFA restated that it that relies on official records and survey information, and that those records support a “low” rating.
Several issues relate to the definitions that CDFA applies in assigning ranks. They are so restrictive that – in my view – they result in underestimates of pathogens’ potential impacts.
One example is how CDFA recognizes first detections of a pathogen. As Bernhardt and Swiecki point out, CDFA’s consideration of only “official” samples prevents timely action to protect California’s agriculture and native vegetation. In the case of P. occultans, CDFA took no action for two years after the pathogen was first reported in the state. This detection had been confirmed by a CDFA laboratory.
A second example is host range. CDFA says it assigns a host range rating of “wide” (rating of “3”) only to pathogens that have host ranges of hundreds of species. This means that pathogens with dozens of known hosts across several plant families are given a ranking of “moderate” (2). Furthermore, the agency considers only “official” samples in defining hosts. This approach precludes consideration of the high probability that additional hosts would be found in future, including federally listed species in the genera Ceanothus and Arctostaphylos. Bernhardt and Swiecki named two additional hosts based on field work. CDFA responded to the second point by adding a reference to the likely expansion of the host range in the “Uncertainty” section of the document.
Similarly, CDFA gives a reproductive potential rating of “3” only to pathogens spread by a vector or that infect seeds.
CDFA staffers who manage specific pests lack authority to change these too stringent ranking criteria. The agency leadership need to adopt more realistic criteria.
CDFA responded by accepting many of the additional factors raised primarily by Bernhardt and Swiecki. This resulted in raising the overall score from 11 to 14, and changing the ranking from “C” to “B”.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
We have a great opportunity to shape future efforts to counter non-native forest pests and diseases. Administration officials are most open to new ideas when they first take office. The same is true of new Congressional leadership.
So now is the time to suggest needed changes!
The USDA Secretary-designate is Tom Vilsack. Of course, he was USDA Secretary during the Obama Administration … so he is not entirely “new” to the issues. However, perspectives and priorities have changed, so now is a good time to urge him to consider new approaches. Furthermore, the Senate Agriculture Committee will hold confirmation hearings for him; we can ask the Senators to advocate for our views during this proceeding.
The House Agriculture Committee has a new Chair, David Scott – from the suburbs of Atlanta, Georgia. Again, this provides an opportunity to suggest new approaches and topics for hearings.
I assume you all are knowledgeable about the numbers and impacts of non-native forest insects and pathogens in the United States, and of the pathways by which they are introduced and spread. If you are not, peruse my blogs about wood packaging or plants as vectors (click on the appropriate “categories” listed at the bottom of the archive of blogs). Or read Fading Forests III (see the link at the end of this blog) and the article I coauthored early this year on improving forest pest management programs.
On the basis of my long experience, I suggest that you encourage USDA Secretary-designate Vilsack, Senators on the Agriculture Committee, and House Agriculture Committee Chair David Scott to consider the following recommendations:
Actions Congress could take
Congress could amend the Plant Protection Act [7 U.S.C. §7701, et seq. (2000)] to prioritize the protection of natural and agricultural resources over the facilitation of trade. This might be done by amending the “findings” section of the statute to give higher priority to pest prevention.
The Agriculture Committees of both the House and Senate could hold hearings on the importation of forest pests. They could determine if the USDA is doing an adequate job protecting the country from insect pests and diseases, and how our defenses could be strengthened. One component of the hearings could focus on whether current funding levels and mechanisms are adequate to support vigorous responses to new pest incursions.
Congress could commission a study of the feasibility, costs and benefits of establishing a “Center for Forest Pest Control and Prevention” to coordinate research and policy on this issue.
Congress could increase funding for the appropriate USDA APHIS and Forest Service programs and activities to enable vigorous containment and eradication responses targeting introduced forest pests and diseases.
Congress could increase funding for USDA research on detection of insects and pathogens in shipping; insect and disease monitoring/surveillance; biological control; alternatives to packaging made from wooden boards; management of established pests; and resistance breeding to enable restoration of impacted tree species.
Actions Secretary-designate Vilsack could initiate without legislative action (once he is confirmed)
Introductions of pests in the wooden crates, pallets, etc., goods come in
APHIS could take emergency action to prohibit use of wood packaging by importers of goods from countries with a record of poor compliance with ISPM#15. This action is allowed under authority of the Plant Protection Act [7 U.S.C. §7701, et seq. (2000)] and Article 5.7 of the World Trade Organization’s Agreement on the Application of Sanitary and Phytosanitary Measures.
APHIS could strengthen enforcement of current regulations by aggressively prosecuting repeat offenders. For instance, APHIS could begin imposing administrative financial penalties on importers each time their wood packaging is non-compliant with ISPM#15.
APHIS could work with Department of Homeland Security Bureau of Customs and Border Protection (CBP) to improve information available to U.S. importers about which foreign suppliers of SWPM and shippers have good vs. bad records of compliance with ISPM#15.
DHS CBP could release information on country of origin and treatment facility for ISPM#15-stamped SWPM that is found to be infested with pests.
USDA APHIS could begin a phased transition from solid wood packaging to alternative materials that cannot carry wood-boring pests. APHIS could initiate a pest risk assessment to justify making such an action permanent. Imports could be packaged in alternative materials, e.g., manufactured wood products (e.g. plywood), metal, or plastic.
Nursery Plant (“Plants for Planting”) Pathway
APHIS could apply authorities under NAPPRA and other existing authorities to curtail imports of plants that pose a high risk of introducing insects and pathogens that would threaten tree species that are important in natural and urban forests in the U.S. At a minimum, APHIS should restrict imports of live plants that are in the same genus as native woody plants of the U.S.
APHIS could work with the Agriculture Research Service and National Institute of Food and Agriculture to determine which taxa of woody vegetation native to the U.S. are vulnerable to pathogens present in natural systems of trade partners. Particularly important would be the many Phytophthora species found by Jung and colleagues in Vietnam, Taiwan, Chile, and other countries. Once the studies are sufficiently complete, APHIS could utilize authority under NAPPRA to prohibit importation of plants from those source countries until effective phytosanitary measures can be identified and adopted.
Other Actions
APHIS could develop procedures to ensure the periodic evaluation of pest approach rates associated with wood packaging and imports of “plants for planting” and highlight areas of program strengths and weaknesses. A good place to start would be to update the study by Haack et al. (2014), which estimated the approach rate in wood packaging a decade ago.
The USDA could expand early detection systems for forest pests, such as the APHIS CAPS program and the Forest Service EDRR program. These programs should be better coordinated with each other and should make better use of citizen observations collected through smartphone apps, professional tree workers such as arborists and utility crews, and university expertise in pest identification and public outreach. An effective program would survey for a broad range of pests as well as for suspicious tree damage, and would be focused on high-risk areas such as forests around seaports, airports, plant nurseries, and facilities such as warehouses that engage in international trade.
The USDA could initiate a “Sentinel Plantings“ network of US tree species planted in gardens abroad and monitored for potential pests and diseases.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
On the first day of winter, Daniel Volk, Forest Health Project Coordinator for Cleveland (OH) Metroparks reported that a coordinated survey has confirmed the presence of beech leaf disease link to DMF in four new states — Massachusetts, New Jersey, Rhode Island, and West Virginia. In all, the disease is now known to be established in 71 counties in the US and Canada. Funding was provided by the USFS Forest Health Management “emerging pest” program.
2021 survey efforts will focus on high risk counties adjacent to affected counties.
Cleveland Metroparks has several resources available on its website and will continue to post updated information there as it becomes available.
I posted a blog urging recipients to participate in these searches last June link I hope you will do so again in 2021.
range of American beech
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
dwarfed Ulmus davidiana; photo by Krzsztof Zianek; Wikipedia Commons
USDA APHIS is seeking public input on a risk assessment that is intended to evaluate the risk of allowing importation of dwarf elm trees (bunjae) from South Korea. Importation of these trees is currently prohibited under APHIS’ authority to require a risk assessment before importation under the NAPPRA program. Upon receiving the Korean request, APHIS must decide whether to maintain the prohibition, or alter it. The risk assessment can be obtained here. Comments are due January 11, 2021.
I urge those with expert knowledge about phytophagous insects, nematodes, and fungal and other pathogens to prepare your own comments to APHIS.
[A year ago, Korea sought permission to export dwarfed maple trees to the U.S. CISP commented on APHIS’ risk assessment at that time; see my blog here. I believe APHIS has not yet decided whether to allow such imports. Many of the same issues apply here.]
After reviewing the risk assessment, I conclude that there are too many high-risk pests to support removing the taxon from the current restrictions. The history of introductions on dwarfed trees in the past supports this conclusion. The most conspicuous is the citrus longhorned beetle (Anoplophora chinensis) – the reason for the original NAPPRA listing – but there have been others, too.
The risk assessment has some strengths. I applaud the assessors for noting in each pest review that since the proposed imports are propagative material, all the pests will arrive on living hosts. The assessment then discusses – briefly! – the mechanisms by which the pest or pathogen could disperse to infest new trees – e.g., flight, rain splash, irrigation water. However, I think the assessment is sometimes too cautious in describing probable invasive risks.
I also find several important weaknesses in both the risk assessment process generally and specific findings.
Weaknesses of the Risk Assessment Process
The assessors do not discuss the potential efficacy of pest-management actions taken by the exporter or by USDA at ports of entry. They outlined production and harvesting practices that they assumed would apply to the exported plants. They warned that the risk assessment finding could not be applied to plants produced or handled other under conditions.
I am troubled by the assessors’ decision not to consider the plants’ ages and sizes. There is evidence that age and size are very important in determining the likelihood of pest presence. Perhaps the decision reflects the assumption that the exported plants would be less than four years old. Still, the assessors should have been transparent about the reasoning behind this decision.
The assessment underestimates “uncertainty”. One manifestation is the decision to provide little information about whether pests or pathogens known to attack several Eurasian species of Ulmus might also attack North American elm species. This gap arises, I believe, from the International Plant Protection Organization (IPPC) and APHIS requirement that risk analysts consider only pest-host relationships described in the literature or inferred from port interception data. I find this narrow approach to be a weakness, given how many unknown pest-host relationships have proved to be highly damaging. This issue arises specifically in the reviews of the nematode Meloinema kerongense and several powdery mildews (Erysiphe kenjiana, E. ulmi and Podosphaera spiralis) – all of which are identified as affecting at least some elm species.
Perhaps the missing information has fewer consequences here, since the NAPPRA process does not require that APHIS prove the pest-host relationship for every pest evaluated in order to justify retaining the prohibition on importation. The well-documented history of detecting the citrus longhorned beetle in artificially dwarfed trees and as a pest of the Ulmus genus provides more than sufficient justification to retain trade restrictions. Still, if APHIS is conducting a formal risk assessment, it should be thorough. Anything else sets an unfortunate precedent.
Finally, in cases when some of the hosts considered are commercial crops – e.g., fruit trees – the assessment often does not include forest trees as economically important resources at risk.
Questions re: some of specific pests in the analysis
3.2.1. Cerambycidae (Coleoptera)
The risk assessment notes the minimal information available regarding several cerambycid beetles present in Korea that are capable of feeding on elm trees. Collectively, these beetles have a wide host range — Acer, Alnus, Citrus, Ficus, Hibiscus, Juglans, Malus, Morus, Quercus, Populus, Prunus, Pyrus, Salix, Sorbus, and Ulmus. The beetles can thrive in the climate present across most of the Lower 48 states (USDA Plant Hardiness Zones 6-9). The risk assessment does mention the risk to urban and forest trees. It also mentions British detection of A. chinensis larvae in twigs of imported maple trees, but for some reason does not mention past U.S. detections and introductions of this beetle in maple bonsai/bunjae trees in Tukwila, Washington. Is this because the detections were 20 years ago? Does the passage of time make the detections any less relevant?
trees removed for CLB eradication in Tukwila, Washington
The analysis of this tortricid moth notes its broad host range, including Abies, Acer, Betula, Fraxinus, Populus, Quercus, Salix, Sorbus, Tilia, and Ulmus. Yet the analysis makes no mention of the potential impact of moth larval feeding on the buds and flowers of forest trees. Nor does it discuss the moth’s impact in Canada, where it is established. The Canadian experience seems quite pertinent and is an obvious omission.
3.2.3. Meloinema kerongens
This nematode is present on elms in Korea. The assessors could find no information on the damage it causes to its hosts there. Again, there is no discussion of possible vulnerability of American elms. Apparently the nematodes are considered likely to survive the importation process, when the trees will be bare root. The assessors say that since the dwarfed trees (once imported) are likely to be planted in pots, that might limit the nematodes’ dispersal into native soil habitats and ability to infect new trees. This finding is troubling because it is likely that nematodes or their eggs could be present in the pots’ soil, and if that soil leaks from the pot or is disposed of during repotting or with other actions, pests could become established in native soil.
3.2.5. Helicobasidium mompa
This fungus causes root rot on multiple genera in 44 plant families. The list of hosts includes Pinus spp., Populus spp., Prunus spp., and Quercus spp. It appears to thrive in a wide climatic range covering virtually the entire Lower 48 states (USDA Plant Hardiness Zones 2-11). The fungus is spread via rain or irrigation water. I note that experience with the Phytophthora genus of brown algae has demonstrated how difficult it can be to control pathogens that spread in rain or irrigation water – in both nurseries and the wild.
Other Potential Pests
I urge experts to review the long list of pests not analyzed—especially the nematodes that inhabit the root and rhizosphere. Analysts did not analyze them because they are ectoparasites; they decided that ectoparasites were unlikely to remain with the dwarfed trees when they are shipped bare-root.
I also wonder whether the mistletoe Viscum album – a parasitic plant – might be spread onto the dwarfed trees by birds perching on branches or shelter structures above the production facilities. Assessors thought that dormant mistletoe on the plants would not be easily detected during visual inspection at the ports.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
