‘Ohi‘a (Metrosideros polymorpha) is the most abundant native forest tree in Hawai`i and of enormous ecological, cultural, and economic importance. Five species of endemic Metrosideros are recognized on the Hawaiian islands. Only one — M. polymorpha — is found throughout the state. Eight varieties are recognized. These varieties inhabit different environments and have adapted to selective pressures characteristic of these locations. There are at least five other species in the Metrosideros genus, each endemic to one or a few nearby islands. Blaine et al. (2022) [full citation at end of this blog] provide a helpful summary of the tree’s ecological importance and its apparently on-going speciation.
‘Ohi‘a provides habitat for endemic birds, insects, and plants, many of which are endangered. Thus, conservation of this species — and all Hawaiian Metrosideros – is vital for the conservation of countless other taxa. In addition, high elevation ʻōhiʻa forests protect vitally important watersheds across the state. For Native Hawaiians, ʻōhiʻa is a physical manifestation of multiple Hawaiian deities so is the subject of many proverbs, chants, stories, and a foundation of scared hula. Finally, the tree is beautiful!
Native Hawaiian forests face multiple threats — invasive animals and plants, wildfire, and land-use changes. Due to such threats, natural ʻōhiʻa regeneration is largely absent in most lower-elevation forests. In this case, competition with invasive species and the presence of diseases such as ʻōhiʻa rust (Austropuccinia psidii) are probably the specific causes. Multiple government and non-governmental entities have made substantial effort to mitigate these threats.
ROD-infected ʻōhiʻa; photo by J.B. Friday
The disease Rapid ‘Ohi‘a Death (ROD) is an unprecedented threat to this species and the forests it constitutes. The disease is caused by two newly described fungal pathogens: Ceratocystis lukuohia and C. huliohia. The disease caused by C. lukuohia is more severe. To date it has been detected on the two islands farthest apart in the chain — Hawai`i (the Big Island) and Kaua‘i. C. huliohia causes a canker disease that kills trees more slowly. It is more widespread, found on Maui and O‘ahu in addition to Hawai`i and Kaua‘i. Blaine et al. (2022) and the profile here describe the two diseases’ epidemiologies, progression, impacts, and challenges.
Because of the clear threat to Hawaiian ecosystems, ecosystem services, and cultural assets, considerable effort has put into delimitation and research on possible mitigation actions since ROD was discovered in 2010. The first strategic plan covered the period 2017–2019. It focused on expanded efforts to map outbreaks, research on the epidemiology of the pathogens, and most-promising management practices. The second strategic plan covers 2020–2024. It provides for continued surveillance and improvement of these technologies; expanding outreach and public engagement; research on possible vectors of the pathogens; collection and preservation of seeds for research and future restoration; and comprehensive evaluation and development of disease resistance in ʻōhiʻa.
Soon after the causal agents were clarified, the USDA Agriculture Research Service (ARS) began screening for disease resistance. By 2016, ARS had demonstrated that five individuals from two varieties of M. polymorpha had survived inoculation by the more virulent pathogen, C. lukuohia. Their survival raised hopes that natural resistance might be present in wild populations of at least some varieties. However, more comprehensive screening of trees from throughout the species’ range is needed to provide an accurate baseline on the frequency, level, and distribution of genetic resistance to both pathogens. The goal is to produce material resistant to both pathogens that can be used to preserve the ecology, culture, and biotic communities that are dependent on this tree species.
To carry the expanded effort forward, in 2018 a collaborative partnership of state, federal, and non-profit groups was formed. Participants in the ‘Ohi‘a Disease Resistance Program (‘ODRP) include: the Akaka Foundation for Tropical Forests; USDA’s Forest Service and Agriculture Research Service; the state’s Division of Forestry and Wildlife and Agriculture Research Center; programs of the University of Hawai‘i at Manoa and at Hilo; Purdue and Arizona State universities; the Tropical Hardwood Tree Improvement and Regeneration Center; and Kalehua Seed Conservation Consulting.
Blaine et al. (2022) have now outlined a framework to guide the overall effort to identify and develop ROD resistance in M. polymorpha and, possibly, all Hawaiian Metrosideros species. The framework calls for the following activities:
(1) evaluating and operationalizing methods for inoculation-based screening and greenhouse-based production of test plants; and
(2) short-term greenhouse screenings of seedlings and rooted cuttings sampled from native Metrosideros throughout Hawai’i.
Once these tasks have been achieved, the effort is expected to expand to address:
(3) establishing field trials to validate the short-term greenhouse assays and monitor durability and stability of resistance;
drivers of susceptibility and resistance to characterize the durability and stability of genetic resistance to ROD;
(5) developing remote sensing and molecular methods to rapidly detect ROD-resistant individuals;
(6) if necessary, conducting breeding to increase the efficacy of resistance and improve durability of ROD resistance; and
(7) supporting already established and ongoing Metrosideros conservation, including state-wide seed collection and banking, with information on not only genotypes resistant to ROD but also production of ROD-resistant seed.
Blaine et al. (2022) outline how to proceed on each step, and describe the challenges that must be overcome. Challenges range from building growing and screening capacity to handle the thousands of plants required, to developing the remote sensing tools to identify diseased trees in the forest, to identifying sites for seed orchards. Actions by ‘ODRP will focus on Stage II screening in the field to examine the durability of resistance under the wide variety of ecological conditions in which ʻōhiʻa grows and in the presence of a potentially evolving pathogen. Resistance studies must expand beyond M. polymorpha varieties from only one island (the Big Island) to include the other Hawaiian Metrosideros taxa.
Once ROD-resistant M. polymorpha trees are discovered and groundwork has been laid to satisfy initial needs for resistant tree seedlings for forest restoration, scientists can begin research into the genetic basis of ROD resistance. This knowledge will assist breeding efforts which might be necessary if resistance to one of the pathogens does not confer resistance to the other, since the goal is to provide seedlings that are resistant to both.
Blaine et al. (2022) note that the state and others continue efforts to address other aspects of ROD management. These include
1) controlling the spread of the pathogen through local quarantines on movement of infected material and increased public education on bio-sanitation for forest users;
2) testing repellants to reduce beetle attack on infected trees and subsequent frass production.
3) reducing wounding of trees by fencing more pristine forests and removing feral ungulates
SOURCE
Blaine C. Luiz, Christian P. Giardina, Lisa M. Keith, Douglass F. Jacobs, Richard A. Sniezko, Marc A. Hughes, James B. Friday, Philip Cannon, Robert Hauff, Kainana Francisco, Marian M. Chau, Nicklos Dudley, Aileen Yeh, Gregory Asner, Roberta E. Martin, Ryan Perroy, Brian J. Tucker, Ale.alani Evangelista, Veronica Fernandez, Chloe Martins-Keli.iho.omalu, Kirie Santos, Rebekah Ohara. 2022. A framework for establishing a rapid ‘Ohia death resistance program. New Forests. https://doi.org/10.1007/s11056-021-09896-5
See also the video at https://www.bigislandvideonews.com/2019/06/16/video-to-save-ohia-a-genetic-resistance-program-will-be-built/
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
vegetation killed by Phytophthora cinnamomi in West Australia
Some invasive species practitioners have been trying to develop a standardized framework for describing bioinvasions. Their goal is to overcome disparities in approaches developed by scientists working with various taxonomic groups in hopes of improving understanding of, and communication about, bioinvasions. Prominent among these efforts is the “Unified Framework for Bioinvasion” published by Blackburn et al. in 2011 (full citation at end of blog).
Now several forest pathologists (Paap et al; full citation at end of blog) say that this framework does not adequately integrate forest pathogens. This omission is particularly unfortunate given the prominence of forest pathogens as damaging invaders – e.g., chestnut blight in Europe and North America; white pine blister rust in North America; sudden oak death in North America and Great Britain; myrtle rust and Phytophthora cinnamomi in Australia. (See profiles of all these pathogens here; I note additional examples in North America, such as laurel wilt disease.)
Paap et al think that this omission impedes understanding of both forest pests and invasive species in general. Also, they say that integrating microorganisms into the broader Blackburn framework would help forest pathologists better understand how and why invasions occur, where they occur, and how they can be stopped or mitigated.
Furthermore, they note the importance of integrating the diverging terminologies used by invasive species practitioners and plant pathologists and their separate regulatory bodies – the Convention on the Conservation of Biological Diversity (CBD) and the International Plant Protection Convention (IPPC). I concur, since nations’ programs regulating plant diseases and their vectors operate under the IPPC rubric.
Figure 2 and Table 1 lay out Paap et al.’s proposed modification of Blackburn’s framework, and detail strategies linked to management goals appropriate for the stages of plant disease development.
Tanoak mortality in southern Oregon caused by P. ramorum – a pathogen completely unknown until it was introduced to North America and Europe; photo by Oregon Department of Forestry
However, such integration will be impeded by many difficulties (I have re-ordered these points):
1) The first – which underlies all others — is the paucity of data on microbial taxa, which undermines the pest risk analyses and other systems developed for assessing and managing other types of invasive species. That is,
Many of the vast number of microbial taxa have not yet been described.
Even species that have been describe often cannot be ascribed to a specific geographic origin. This information gap undercuts efforts to determine whether a disease outbreak is caused by an “introduced” organism.
2) Microbial species are usually detected only when disease impacts become obvious. However, an outbreak might not signal a new or spreading “introduction”. While invasive species must—by definition—cross a geographic boundary (through the assistance of human actions), pathogens can cause disease outbreaks through breaching a wider range of boundaries, including ecological and evolutionary ones. Thus, the disease outbreak doesn’t always fit the definition of “invasive species”.
3) Substantial differences exist in training and goals between fields. Forest pathologists are usually trained in plant pathology (often focused on crops) rather than in forestry or ecology. Their goal is to manage the pathogen. Invasion scientists tend to focus on natural ecosystems, study animal and plant invasions, and seek understanding of the invasion process.
4) A related issue is that the two fields operate under separate regulatory bodies that have different emphases and aims. Paap et al. note that while the IPPC ostensibly includes impacts on natural environments, its members’ priority is plants of economic importance. The World Trade Organization’s Agreement on the Application of Sanitary and Phytosanitary Measures (WTO SPS) seeks primarily to minimize disruption of trade resulting from plant health regulation. On the other hand, the CBD explicitly considers invasive species’ impact to the natural environment (Aichi Biodiversity Target 9). [To read my critique of the WTO SPS and IPPC, read the Fading Forests reports (link at end of this blog), especially FF II.]
Rome – home to the IPPC
They note that in 2004, the IPPC and CBD secretariats established a Memorandum of Cooperation to promote synergy and to avoid duplication. Paap et al. appear disappointed that despite development of joint work plans, phytosanitary programs are still focused largely on crop pathogens.
Disease development – a complex set of circumstances that makes risk assessment less reliable
Since I am not a pathologist (or even a biologist), I learned a lot about the complexities of plant pathology from Paap et al.
While I am certainly familiar with the “disease triangle” concept, I had not thought about certain implications. For example, pathogens can cause severe disease outbreaks by evading any one of three types of barriers: geographic, environmental, or evolutionary. Transport of the micro-organism to a new ecosystem (leaping the geographic barrier and meeting the definition of an “introduction” in invasive species terminology) certainly can facilitate disease outbreaks. However, evolutionary and environmental barriers might also be overcome in other ways.
The result is that a plant disease can develop under multiple scenarios following the introduction of an alien pathogen. These scenarios are:
disease on a coevolved host growing as an alien species in the new environment, for example plantations of trees grown for timber (pathogen reunion);
disease on a naïve host that is itself alien to the geographic region in question (host jump);
disease on an alien host (naïve or coevolved) which supports disease on a host native to the new geographic area that could not be sustained in the absence of the alien host;
disease on alien and native hosts; and
disease on a host native to the new geographic area but not on an alien host.
Countries’ efforts to conduct pest risk analyses are unlikely to be straightforward – or even possible – with so many disease scenarios
Paap et al. proceed to compare introductory pathways under the CBD categorization and plant pathology. In doing so they point out several aspects of introduction, establishment, and spread that are specific to pathogens. For example, trees’ long life spans and inability to adapt as rapidly as the micro-organism increase their vulnerability to devastating disease outbreaks following the arrival of a novel pathogen.
Participants in the Montesclaros meeting that drafted an early critique of international phytosanitary procedures
Paap et al. reinforce points made by other critics of current phytosanitary programs. (See my earlier blogs under the category “plants as pest vectors”.) In particular, they point out the weakness of visual inspection and note that new molecular assays can detect only known microorganisms. An additional complication is that DNA can persist in soil and plant tissue after death of the organism, leading to false positives. RNA is cannot yet be used as a viability marker.
Paap et al. provide three case studies to illustrate in greater depth several major challenges encountered when managing invasive forest pathogens. Most of these weaknesses are well known to forest pathologists.
1. The inconspicuous nature of microorganisms
As noted by Paap et al. and other authors, the difficulty detecting microbes is exacerbated by the huge volumes of goods, especially live plants, in international trade; the small proportion of those plants that can be inspected; the weakness of visual examination; application of fungicides and fertilizers before export that suppress symptoms. The chosen example is the oomycete genus Phytophthora, specifically P. ramorum.
2. Cryptic status of many species
Current biosecurity programs rely on naming the organism and its place of origin. This is actually impossible for many microorganisms. The tardy response to ash dieback (Hymenoscyphus fraxineus) in Europe illustrates the delay in determining the causal agent and its geographic origin. During this nearly two-decade period the possibility of preventing spread was lost.
3. Rapid evolution
Rapid evolution of the introduced pathogen can overcome resistance in a host. The example described is Cronartium ribicola (causal agent of white pine blister rust) on Western white pine (Pinus monticola) and sugar pine (P. lambertiana). They also mention the threat from hybridization between previously isolated populations, specifically Phytophthora x alni causing a devastating decline of black alder in Europe.
Sugar pine in Sequoia National Park; photo by S. Rae via Flickr
Paap et al. call for increased research to increase our knowledge of microbial diversity, especially in taxonomically rich and poorly studied ecosystems. They praise sentinel plantings as a powerful tool for early warning of pathogen threats.
SOURCES
Blackburn, T.M., P. Pysek, S. Bacher, J.T. Carlton, R.P. Duncan, V. Jarosik, et al. A proposed unified framework for biological invasions. Trends Ecol Evol. 2011; 26(7):333-9.
Paap, T., M.J. Wingfield, T.I. Burgess, J.R.U. Wilson, D.M. Richardson, A. Santini. 2022. Invasion Frameworks: a Forest Pathogen Perspective. FOREST PATHOLOGY https://doi.org/10.1007/s40725-021-00157-4
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
Eucalyptus plantation in Kwa-Zulu-Natal, South Africa; Kwa-Zulu-Natal Dept. of Transportation
Graziosi et al. (full citation at the end of the blog) point out that trees are crucial for Africa’s future. Eight hundred of the 4,500–6,000 indigenous tree species provide significant food. As elsewhere, trees provide wood and other extractive resources essential for economic growth. They also support biodiversity and mitigate current and impending climatic variations. Africa– especially the Sub-Saharan countries – is already considered highly vulnerable to climate change.
According to Graziosi et al., the cumulative economic impact of all invasive species in Africa is expected to exceed $1.2 billion per year. The total invasion cost as a proportion of GDP for many African countries is among the highest in the world. This raises the stakes for developing locally appropriate management strategies across the continent.
Responding effectively to this threat is hampered by gaps in data as well as some countries’ limited capacity for biosecurity. Graziosi et al. say that improved knowledge of taxonomy, distribution, and damage caused by these organisms is essential. Such knoledge will be crucial to develop continent-wide strategies to manage this emergency and to enhance capacity for country-level interventions.
Native and alien pests. Indigenous and plantation trees
Africa’s trees and their services are threatened by both native pests and accelerating introductions of pests and diseases from elsewhere. Long-established and new invaders increasingly affect planted forests of exotic eucalypts, pines, and Australian acacias, as well as important indigenous trees. Graziosi et al. note that the U.N. Food and Agriculture Organization (FAO) in an annex to a report issued in 2009 recorded about100 species of forest pests affecting trees in planted and natural forests across Africa. Half are native insects and pathogens, a third are alien; about 15% are of unknown origin. Considering all pests, broadleaf trees (predominantly native) are most affected.
The result is damage from the local – e.g., to rural livelihoods – to the continental – e.g., to economic development and biological diversity across Africa. Moreover, pests exacerbate widespread loss of forest cover. Overall, African forests are shrinking at the rate of almost 0.5% annually. This deforestation is affecting particularly natural forests; planted forests are actually growing 1.3% annually.
Exotic plantation trees face severe threats. More than 47 native and 19 non-indigenous defoliators, sap-feeders, wood- and shoot-borers attack plantations of Acacia spp., Eucalyptus spp., Pinus spp., and teak (Tectona grandis). About 90% of pathogens of plantation forestry are either non-indigenous or of uncertain origin. Eucalyptus alone are severely damaged by 15 species of pathogens. These organisms are listed in Tables 1 and 2.
Numerous native insect species, known as pests of indigenous trees, have reportedly widened their host range and now damage exotic trees too. Some introduced insects appear to pose significant threats to native tree species. One example is the Cypress aphid Cinara cupressi, which is attacking both exotic cypress plantations and the native African cedar Juniperus procera. Some fungi in the family Botryosphaeriaceae are latent pathogens infecting a wide range of hosts including indigenous Acacia. Dieback of large baobab trees was recently reported from southern Africa. While various microorganisms are associated with these symptoms, the specific cause is still uncertain.
A baobab tree in Limpopo region of South Africa; Wikimedia
The risk currently appears to be particularly high in South Africa. The country’s flora is highly diverse and has a high level of endemism. In fact, South Africa is home to the Earth’s smallest floral kingdom, the Cape Floral Kingdom. It is also the apparent hot spot for pest introductions from overseas (see below). Phytophthora cinnamomi is attacking native Proteaceae in South Africa. According to Graziosi et al., an “incredible diversity” of Phytophthora taxa is present, portending threats to additional plant species. Other pathogens are attacking native conifers in the Podocarpus genus, Ekebergia capensis (Meliaceae), and Syzygium trees.
Protea repens and fynbos vegetation near Table Mountain; photo by Mike Wingfield
There is a clear pattern to further spread: pests first introduced to South Africa often spread. Examples include several insects and pathogens on Eucalyptus and the wood-boring pest of pine Sirex noctilio. This pattern is explained by two main factors. South Africa has a high capacity to detect introduced species. Also, there is an active plantation forestry sector that imports propagules. This offers opportunities for contaminating organisms to be introduced simultaneously.
Furthermore, as Graziosi et al. note, determining the geographic origin of significant proportion of pathogens is extremely difficult – an issue I will discuss in a separate blog based on a publication by primarily South African scientists. Some non-indigenous pathogens have been on the African continent for a long time. The Armillaria root rot pathogen apparently was introduced to South Africa with potted plants from Europe in the 1600s! They note also that many non-indigenous pathogens are probably already established on the continent but not yet detected due to the organisms’ cryptic nature and lagging detection abilities.
The future of African forests
African countries expect economic growth with associated increased trade with countries off-continent. The probable result will be to accelerate the rate of species introductions and spread. However, as climate change worsens, managers will find it increasingly difficult both to predict introduced species’ impact and to implement management programs.
This led Graziosi et al. to call for urgent improvements in plant biosecurity across the continent. They advocate improved coordination at regional and international levels. The list of needed actions is a familiar one: development and application of improved diagnostic tools, updated plant exchange regulations, and revised trade policies.
Graziosi et al. also call for development of effective control and management options. They suggest biocontrol, innovative silviculture practices, and selection of resistant trees. The good news is that African countries have already initiated programs to conserve tree germplasm and domesticate indigenous species, including establishment of field gene banks of high-priority indigenous trees. I have previously praised South African efforts, specifically reports here and here.
Mudada, Mapope, and Ngezimana (2022) describe the risk from introduced species to agriculture and human well-being in southern Africa beyond forestry. The region is already ravaged by food insecurities and hidden hunger. It would be devastated if the global average of crop loss due to plant diseases (10-16%) occurs there. They say these losses can be avoided with improved biosecurity mechanisms focused primarily on pest exclusion and plant quarantine regulations.
SOURCES
Graziosi, I. M. Tembo, J. Kuate, A. Muchugi. 2020 Pests and diseases of trees in Africa: A growing continental emergency. Plants People Planet DOI: 10.1002/ppp3.31
Mudada, N. Mapope, N., and Ngezimana, W. 2022 – The threat of transboundary plant pathogens to agricultural trade in Southern Africa: a perspective on Zimbabwe’s plant biosecurity – A review. Plant Pathology & Quarantine 12(1), 1–33, Doi 10.5943/ppq/12/1/1
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 the United States and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
The surge in US imports from Asia that began in the second half of 2020 continued through 2021 and into January 2022. As of September 2021, import volumes from Asia averaged almost 20% higher than the historical monthly average for every month of 2021 (Mongelluzzo, October 13, 2021). The surge continued into 2022. In January 2022, US containerized imports from Asia hit the highest monthly total ever recorded — 1.7 million TEU. This was a 14.6% increase over December 2021 – and a 4.5% increase from a year earlier (January 2021). [Mongelluzzo Feb 23]
The 2022 increase in import volumes was on top of the record-breaking levels seen in 2021. For example, average monthly import volumes during 2021 at the principal ports for receipt of goods from Asia — Los Angeles-Long Beach — were 23% over the 2019 average (Mongeluzzo April 2021).
Increases in volume from December 2021 occurred at ports across the country. Pacific coast ports saw increases – 25.8% at the LA/LB complex (which handles ~50% of US imports from Asia); 39.1% at Northwest Seaport Alliance (Seattle and Tacoma); 19.7% at Oakland. So did ports in the Southeast – 12.7% in Savannah and 14.1% in Charleston. However, New York/New Jersey saw a decrease of 2.2% and Norfolk saw a decrease of 10.6%. [Mongelluzzo Feb 23] New York had seen a steep increase in mid-2021 (Angell Dec. 22, 2021), but apparently this did not hold up through the year.
The southern California ports report that ships leaving China in early March will – as expected – increase import volumes before the end of the month. Long Beach projected that numbers of arriving shipping containers will rise 34% in the week beginning March 20, compared with the week of March 7; Los Angeles projected an increase of 63% [Mongelluzzo March 10].
port of Mobile
Volumes Will Probably Continue to Rise Along the Gulf
Containerized imports from Asia through US Gulf ports had risen 27.2% to 1.14 million TEU in 2021. At the port of Mobile, specifically, imports from Asia last year rose 25% from 2020 to 230,347 TEU in 2021. Imports from Asia through Houston jumped 34 % to 807,376 TEU in 2021 [Mongelluzzo Feb 2 2022]
Increasing manufacturing and distribution industries in the Gulf region are probably an important factor in rising import volumes there. Mongelluzzo Feb 2 2022 notes the presence of a Hyundai factory in Alabama, a Tesla factory and Amazon fulfillment center near Austin, as well as several retail chains’ distribution centers near Houston. Many of these facilities opened in 2021.
Import volumes entering via Gulf and Southeastern ports are expected to continue growing in coming months and years. Several carriers have announced new direct Asia-to-US-east coast transport services. These include South Korea’s HMM (to Houston); CMA CGM; and Maersk (Vietnam and China to Houston and Norfolk; China and Indonesia to Charleston and Newark)
Those who follow shipping expect import volumes to drop in February because many factories in Asia were closed for two weeks or more for the Lunar New Year holidays, which began on Febrary 1. Imports should surge again in March. [Mongelluzzo Feb 23]
The Risk
Remember, Asia is the origin of many of the most damaging forest pests. These include Asian longhorned beetle, emerald ash borer, redbay ambrosia beetle, phytophagous and Kuroshia shot hole borers (for profiles of each visit here). Indeed, 15 of 16 non-native bark beetles in the Xyleborini (a tribe of ambrosia beetles) detected in the United States since 2000 are from Asia (Bob Rabaglia, USFS Forest Health Protection, presentation at IUFRO meeting in Prague, September 2021).
It seems to me that the beetles native to southeast Asia, e.g., the phytophagous and Kuroshio shot hole borers, are likely to find the climate along the Gulf of Mexico to their liking. Indeed, the redbay ambrosia beetle profile already has!
dead redbay in Georgia killed by laurel wilt disease
Li et al. (2021) assessed fungi associated with Eurasian bark and ambrosia beetles and their potential to impact North American trees. They assessed 111 fungal associates of 55 beetle species. They found that none was “highly virulent” on four important pines or oaks of the Southeast. However, I note two caveats. First, they tested only four host species – two pines (Pinus taeda and P. elliottii var. elliottii) and two oaks (Quercus shumardii and Q. virginiana). They did not test against the many other tree species that comprise important components of forests of the region. Second, their bar for concern was extremely high: to qualify as “highly virulent,” the pathogens had to be as damaging as laurel wilt disease or Dutch elm disease! Both have had extremely damaging impacts on their hosts across North America.
Updated Haack Analysis
As has been documented repeatedly (e.g., my blogs), the current approach to curtailing pest introductions associated with wood packaging is not sufficiently effective. Customs officials continue to detect live quarantine pests in wood packaging as it enters the country. However, the exact level of this threat is unclear since the only assessment was based on data from 2009 (Haack et al., 2014). I eagerly await the results of Bob Haack’s updated analysis, which I hope will be published by mid-year.
Haack, R.A., K.O. Britton, E.G. Brockerhoff, J.F. Cavey, L.J. Garrett. 2014. Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States. PLoS ONE 9(5): e96611. doi:10.1371/journal.pone.0096611
Li, Y., C. Bateman, J. Skelton, B. Wang, A. Black, Y-T. Huang, A. Gonzalez, M.A. Jusino, Z.J. Nolen, S. Freeman, Z. Mendel, C-Y. Chen, H-F. Li, M. Kolařík, M. Knížek, J-H. Park, W. Sittichaya, P. H. Thai, S. Ito, M. Torii, L. Gao, A.J. Johnson, M. Lu, J. Sun, Z. Zhang, D.C. Adams, J. Hulcr. 2021. Pre-invasion assessment of exotic bark beetle-vectored fungi to detect tree-killing pathogens. Phytopathology. https://doi.org/10.1094/PHYTO-01-21-0041-R
Mongelluzzo, B. September imports show no relief for stressed US ports. Journal of Commerce. Oct. 12, 2021. https://www.joc.com/port-news/us-ports/september-imports-show-no-relief-stressed-us-ports_20211013.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%2010%2F14%2F21_PC00000_e-production_E-116084_KB_1014_0617
The Invasive Species Prevention and Forest Restoration Act (H.R. 1389) is before Congress. It is co-sponsored by Reps. Peter Welch [VT], Ann Kuster and Chris Pappas [NH], Chellie Pingree [ME], Elise Stefanik and Antonio Delgado [NY], Brian Fitzpatrick [PA], Mike Thompson [CA], Deborah Ross [NC].
Ask your Member of Congress/Representative to co-sponsor this bill. Ask your Senators to sponsor a companion bill.
In summary, this bill will:
Expand USDA APHIS’ access to emergency funds to eradicate or contain newly detected pest outbreaks.
Establish a pair of grant programs to support strategies aimed at restoring tree species decimated by non-native plant pests or noxious weeds. Such strategies include biological control of pests and enhancement of a tree host’s pest resistance.
One grant program supports research to explore and develop these strategies.
The second program support application of resistance breeding and other measures to restore forest tree species. Funded programs must incorporate a majority of the following components: collection and conservation of native tree genetic material; production of sufficient numbers of propagules; preparation of planting sites in the species’ former habitat; planting and post-planting maintenance.
Mandate a study to identify actions to overcome the shortfall of mission, leadership, and prioritization; identify agencies’ expertise and resources; improve coordination among agencies and with partners; and develop national strategies for saving tree species.
Organizations eligible for these grants include federal agencies; state cooperative institutions; colleges or universities offering a degree in the study of food, forestry, and agricultural sciences; and nonprofit entities with non-profit status per §501(c)(3) of the Internal Revenue Code.
Endorsements: Vermont Woodlands Association, American Forest Foundation, The Association of Consulting Foresters (ACF), Audubon Vermont, Center for Invasive Species Prevention, Ecological Society of America, Entomological Society of America, Maine Woodland Owners Association, Massachusetts Forest Alliance, National Association of State Foresters (NASF), National Woodland Owners Association (NWOA), The Nature Conservancy (TNC) Vermont, New Hampshire Timberland Owners Association, North American Invasive Species Management Association (NAISMA), Pennsylvania Forestry Association, Reduce Risk from Invasive Species Coalition, The Society of American Foresters (SAF), and a broad group of university professors and scientists.
Legislative Point of Contact: Alex Piper, Legislative Assistant, office of Rep. Welch. Contact me – providing your email! – if you wish me to send you Alex’ contact information. [The “contact” form does not provide your email and I will not reply in a public way.]
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
I recently posted a blog based on a new report evaluating Canada’s invasive species efforts across all taxa (see Reid et al. reference at the end of this blog). That report focused on federal measures aimed at preventing introductions, including cross-border introductions from the U.S. After posting that blog I learned about a second report by Allison, Marcotte, Noseworthy and Ramsfield (2021) that focuses on non-native insects and diseases that threaten Canada’s trees and forests.
The first report’s authors lamented that invasive species responsibilities are divided among several agencies, depending on the associated commodity or resource. It noted claims by the Canadian government in its 2018 report to the Convention on Biological Diversity to have identified priority pathways. These included several relevant to forest pests: shipping, horticulture, transport containers, and recreation. The Government claimed that the wood packaging, forestry products, and plant products pathways were at least partially regulated and also that national plans had been developed for several priority species, including the Asian subspecies of Lymantriadispar and the emerald ash borer. Reid et al. (2021) included four case studies, two of which dealt with non-native forest pests: successful eradication (the second time around) of the Asian longhorned beetle (ALB); and the high threat to Canada posed by the spotted lanternfly (SLF).
I was pleased to learn of the second 2021 report (Allison, et al.) because of its focus on pests in trees and forests. This is important because U.S. and Canada share four types of forests; evergreen needle leaf forests, sparse trees/parkland, mixed broadleaf / needle leaf forests, and deciduous broadleaf forests (See Fading Forests III, Chap. 1, Fig. 1, Box 2 [link at end of this blog]). Together, North American forests are comprised of 1,165 different native tree species. They offer many potential hosts to any introduced insect or pathogen. Thus the two countries need to coordinate pest-prevention and responses when prevention fails.
It is more likely that a pest from overseas will be introduced first to the U.S. because the U.S. imports a much higher volume of goods and has greater variety of climates and forests. Data show this: as of 2010, more than 181 exotic insects that feed on woody plants were established in Canada (USDA 2009) compared to at least 475 in the U.S. (Aukema et al. 2010). However, sometimes a pest is first introduced in Canada, then spreads south. One examples is beech bark disease.
areas affected by beech bark disease
Forests occupy 40% of Canada’s land cover. Because the country is so large, there are a wide variety of ecozones and forest regions. Almost all (95%) regenerate naturally; 90% are publicly owned (federal and provincial). These forests, which equate to 9% of the Earth’s total forest area, are important not just to Canadians but also to the world for water regulation, carbon sequestration, habitat for biological diversity and the economy. (See Fig.1 in Allison et al.)
Both Canadian reports emphasize Canada’s international obligations, especially under the Convention on Conservation of Biodiversity (CBD). (This is far more than in similar U.S. reports; of course, the U.S. is not a party to this convention.) Allison et al. also mention the Montréal Process Working Group on Criteria and Indicators for the Conservation and Sustainable Management of Temperate and Boreal Forests; international carbon emission mandates and agreements; and the International Plant Protection Convention (IPPC). Allison et al. also stress the importance of international collaborative research, mentioning the International Forestry Quarantine and Regulations Group (IFQRG), expert groups convened by the IPPC and North American Plant Protection Organization (NAPPO), Plant Health Quadrilateral Working Group and participation in the annual USDA interagency research forum on invasive species.
Both new Canadian reports focus on federal efforts, especially those of the Canadian Food Inspection Agency (CFIA), Canada Border Services Agency (CBSA), and Canadian Forest Service of Natural Resources Canada (CFS).
CFIA (Canada’s national plant protection organization, or NPPO in IPPC parlance) is responsible for analyzing risks, setting policy, and managing responses to forest biosecurity incursions. Its authority comes from Canada’s Plant Protection Act and Regulations (S.C. 1990, c. 22). The CBSA enforces regulations at most, but not all, international ports of entry. The CFS conducts research and analysis to support development and implementation of phytosanitary regulations. CFS is also charged with maintaining market competitiveness for forest products and meeting the country’s global commitments to sustainably develop its natural resources. The 10 provinces and three northern territories have jurisdiction over most of the country’s forests, including promoting forest health. Thus, protection and management of Canada’s forests is a shared responsibility among federal, provincial, territorial, municipal and indigenous governments and other stakeholders including the forest industry and non-governmental organizations.
Allison et al. (2021) discuss the effects of invasions on forest ecosystems, including altering forest ecology and the ability of forest ecosystems to provide services. For instance, invasions can change: competitive interactions among tree species; forest food webs; microenvironments; nutrient cycles; successional trajectories; understory plant communities; transpiration rates; water dynamics; and nitrogen and carbon flows, including carbon sequestration and storage. They cite the emerald ash borer and Dutch elm disease as examples.
Much of these authors’ discussion of invasion processes, bioinvaders’ impacts and biosecurity procedures is familiar from a U.S. point of view. However, I appreciate that they explicitly concede knowledge gaps in three particular situations.
First, when discussing the absence of recognized ecological impacts associated with most introduced forest insects and pathogens, they state that this lack of known impacts is often likely due to an incomplete understanding of complex phenomena and delays in perception of effects. They cite — again — the case of the emerald ash borer, when impacts were reported only 10 years or more after its establishment.
Second is their discussion of the drivers of invasion. After saying that the interactions of species’ traits, introductory pathways, and receiving habitats are incompletely understood, they note that it is difficult to determine the relative contribution of reproductive traits and propagule pressure in explaining the invasion success of Hemiptera – which reproduce asexually but are also extremely common in invasion pathways. As I have said in a previous blog, the report due by Haack and colleagues later this year can help clarify the current contribution of the wood packaging pathway to propagule pressure.
Third, they note the limited predictive power of border interception records – and possibly other data resources such as risk assessments, surveillance programs – as a basis for understanding pathways. They note that Ips typographus has been intercepted hundreds of times by North American authorities but has never established.
There are some puzzling gaps in Allison, et al. For example, in discussing the costs associated with forest pest introductions, they do not mention the risk to “leaf-peeper” tourism – as U.S. evaluations of the Asian longhorned beetle do. In discussing the role of propagule pressure they mention pathway volume (i.e., the amount and frequency of trade) and the invasive species’ population levels in the point of origin, but not the invader’s ability to exploit the pathway. (Perhaps that is assumed within the pathway volume measurement?) The example cited is heightened arrivals of Lymantria dispar asiatica during periods of outbreak in its native Asian range.
The report provides helpful clarity on Canadian biosecurity practices. For example, wood packaging entering the country at thefour main Canadian commercial marine ports (Halifax, Montreal, Vancouver, and Prince Rupert) is inspected by CBSA. However, CFIA enforces compliance at the other marine ports and along the 8,891 km (5,500 mile) land-border with the U.S. Apparently CBSA joins in “border blitzes” at selected strategic land-border crossings.
In discussing the provinces’ efforts to slow the spread of established pests, the report mentions the western efforts to prevent introduction of Dutch elm disease. Also, it covers British Columbia’s attempt to prevent spread of balsam woolly adelgid (BWA) into its interior. (I mourn that this effort was not successful.)
elm zigzag sawfly; photo by Georgy Csoka
The report cites the first record of the elm zigzag sawfly, Aproceros leucopoda in North America as an example of citizen detections.
I note that a periodic reassessment of the Canadian regulations governing emerald ash borer in 2014 resulted in a decision to expand the regulated area to reduce regulatory burden, increase awareness of the regulated areas, and maximize compliance. I regret that USDA APHIS decided to fully de-regulate the pest instead. Canada similarly expanded the regulatory zone for a second pest, the brown spruce longhorned beetle (in 2015).
Canada has deregulated pests judged to have spread to the limits of their potential invaded range, e.g., the Pine shoot beetle, Tomicus piniperda.
The report includes three case studies.
whitebark pine infected by WPBR; photo by FT Campbell
This pathogen was introduced more than 100 years ago and has caused extensive damage to Canadian populations of the commercial species western white pine (Pinus monticola) and eastern white pine (P. strobus). It has also contributed to the decline of whitebark pine (P. albicaulis) and limber pine (P. flexilis). An early warning by Gussow (in 1916) about the pathogen’s probable impact apparently led Canada to prohibit further imports of five-needle pines.
Multiple consequences followed the pathogen’s spread. These included reduced volumes of eastern and western white pine due to the combined effects of disease-caused mortality and foresters shifting to alternative species to avoid future losses. Furthermore, both whitebark and limber pines have been ranked as “Endangered” by the Committee on the Status of Endangered Wildlife in Canada. Whitebark pine is also listed on Schedule 1 of the federal Species at Risk Act; limber pine is currently under consideration for such listing.
The report concludes by stating that resistance breeding is an important strategy and that extensive work has been carried out by both the U.S. and Canada.
After noting that this pest of maples is of high concern in Canada, the report lays out the history of the first and second detections in Toronto. Because a risk assessment had been completed beforehand, actions could be taken rapidly. CFIA was encouraged to pursue eradication by the success of several previous eradication efforts, as well as the significant negative impact anticipated to the economy. The Ontario Ministry of Natural Resources, NRCan-CFS, the cities of Toronto and Vaughan, and regional authorities and USDA – which shared information – all contributed. The program removed 5,000 trees in the first six months. In 2018, after five consecutive years of no detections, the ALB was declared eradicated. However, four months later, another ALB was reported – two km from the boundary of the first regulated area. The program was renewed, over a larger area. In total, considering both detections, more than 36,000 trees have been removed. Eradication of the pest following the second detection was declared in June 2020.
The report attributes success to 1) surveillance following IPPC guidelines; 2) reliance on science for evidence-based decision-making, including input on several issued by a science committee chaired by CFS; 3) Early engagement of partners and proactive communication that increased public awareness and reporting.
Oak Wilt Case Study
Oak wilt is established in U.S. states that border Ontario. Also, models suggest that the disease (Bretziella fagacearum) would not be limited by Canada’s climate and that it would cause serious economic harm. Therefore, Canada considers it to pose a high risk. Consequently, CFIA led development of a response framework to guide an incursion response. As usual, this was done in collaboration with representatives from federal, provincial and municipal governments, plus New York and Michigan.
Oak wilt is regulated under the federal Plant Protection Act. In addition to adopting various CFIA directives related to imports, the framework includes a communication strategy; provisions for detection and monitoring; and management activities aimed at its eradication if it is discovered in Canada. The framework also identified research needs and provided funding to address them. map from photos
In their conclusion, Allison, et al. (2021) state that the close relationship between CFIA and CFS is unusual but do not explain how or why.
They also suggest several ways Canada’s biosecurity efforts targetting non-native forest pests could be improved. The first is to increase information-sharing between agencies and with partners, plus better integration of information into policy development. Also, they suggest adoption of new post-border technologies (e.g., “smart” technologies; in-field chemical analyses, and optimization of surveillance programs) and additional research to build a stronger scientific understanding of pest biology, epidemiology, and trade economics. Generally, their recommendations do not overlap with those of Reidet al. (2021) – which was probably being written at the same time. They do both seem to suggest: 1) strengthening partnerships with the public and Indigenous communities and 2) to be prepared to adapt to future conditions.
SOURCES
Allison JD, Marcotte M, Noseworthy M and Ramsfield T (2021) Forest Biosecurity in Canada – An Integrated Multi-Agency Approach. Front. For. Glob. Change 4:700825. doi: 10.3389/ffgc.2021.700825 Frontiers in Forests and Global Change July 2021 | Volume 4 | Article 700825
Aukema, J.E., D.G. McCullough, B. Von Holle, A.M. Liebhold, . Britton, and S.J. Frankel. 2010. Historical Accumulation of Nonindigenous Forest Pests in the Continental United States. BioScience • December 2010 / Vol. 60 No. 11 www.biosciencemag.org
Reid CH, Hudgins EJ, Guay JD, Patterson S, Medd AM, Cooke SJ, and Bennett JR. 2021. The state of Canada’s biosecurity efforts to protect BD from species invasions. FACETS 6: 1922– 1954. doi:10.1139/facets-2021-0012 Published by: Canadian Science Publishing connorreid@cmail.carleton.ca
United States Department of Agriculture, Animal and Plant Health Inspection Service. 2009. Risk analysis for the movement of solid wood packaging material (WPM) from Canada into the US.
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
American beech (Fagus grandifolia) is a widespread and beautiful tree of the eastern deciduous forest. Its range reaches from Nova Scotia to eastern Wisconsin, then south to Mississippi and Louisiana and east to mid-Georgia. It is an important food source for 40 wildlife species, particularly in the northern parts of its range where few other species produce hard mast. (See Lovett et al. 2006.)
Threats
Unfortunately American beech is under threat from three non-native organisms or complexes: 1) beech bark disease, 2) beech leaf disease, and 3) beech leaf mining weevil. A fourth pest, a previously unknown – and still unnamed bark beetle in the genus Agrilus – has been detected in New York City on European beech trees. It is not yet known whether it will attack American beech and, if so, whether it will also cause serious damage (Michael Bohne, USFS, pers. comm.)
symptoms of beech bark disease; photo by Linda Haugen, USFS; via Bugwood
Beech bark disease (BBD) results from the interaction of the introduced European beech scale insect (Cryptococcus fagisuga) and several fungi in the Neonectria genus – some of which are also introduced. The resulting disease has been killing American beech trees since the beginning of the 20th Century. It has spread from Nova Scotia to much of the tree’s range. It has dramatically altered the composition and structure of stands containing beech.
symptoms of beech leaf disease; photo provided by Jennifer Koch, USFS
Beech leaf disease (BLD) was initially detected in 2012, near Cleveland. As of December, 2021, it has spread due east across New York, Pennsylvania, and New Jersey to the Atlantic, then up the coast through Connecticut and eastern Massachusetts, with a separate outbreak in central Maine. The disease is apparently associated with a nematode, Litylenchus crenatae ssp. mccanni, although additional pathogens, like bacteria, might also play a role. The origin of the North American population of the nematode is unknown; it is a related but separate subspecies from a Japanese nematode (Reed et al. 2022).
American beech defoliated by leaf mining weevil; photo courtesy of Jon Sweeney, CFS
Beech leaf mining weevil (Orchestes fagi) is, so far, limited to Nova Scotia. However, it is expected that the weevil will continue spreading throughout the range of American beech through both natural dispersal and human-assisted movement. Repeated defoliation by the weevil might increases mortality rates in forests that are surviving in the “aftermath” stage of BBD (Sweeney et al. 2020).
A new study (Reed et al. 2022) concludes that, despite being detected only 10 years ago, BLD has already become pervasive in forests surrounding Lake Erie in the U.S. and Ontario. While somewhat more prevalent in U.S. states on the eastern side of the Great Lakes (on 54% of trees) than in Ontario (on 46% of trees), BLD is spreading rapidly and affecting every canopy layer. Mortality is highest in seedlings and saplings; understory saplings die within 2 – 5 years. The occasional mortality of overstory trees occurs within seven years of [observed] infection. Defoliation and mortality of saplings allow more light to pass through to the understory; this is expected to alter plant communities on the forest floor.
Beech scale is more widespread in Ontario (found on 60% of trees) than in the U.S. (38% of trees). This is not surprising since the scale was detected in Ontario in 1960, 24 years before it was detected in portions of Ohio, New York and Pennsylvania included in the study (in 1984). Throughout this region, beech scale is disproportionately affecting overstory trees.
Only 4% of trees throughout the study area are infected with Neonectria cankers. In other words, full-scale beech bark disease is not yet widespread and is spreading surprisingly slowly. Scientists do not understand this phenomenon.
These findings are based on a network of monitoring plots a network of monitoring plots set up in 2019 set up in areas surrounding the Great Lakes. They comprise 34 plots at 17 locations in southwest Ontario and 30 plots at 25 locations in Ohio, Pennsylvania, and New York. In total the plots hold 646 live American beech trees — 412 saplings; 85 in the intermediate/suppressed (subcanopy) category; and 149 in the dominant/codominant (canopy) class.
Forest composition is similar throughout the study area. The most common species in association with American beech are sugar and red maples (Acer spp.), and white and green ash (Fraxinus spp.). Other tree species present include eastern hemlock (Tsuga canadensis), white pine (Pinus strobus), oaks (Quercus spp.), and birches (Betula spp.). Study plots had few invasive plants – although the invasive species present are well-documented to invade forests.
Ontario disease assessment
In Ontario, BLD was identified in 25 of the 34 plots. It was present on 171 saplings, 53 intermediate trees, and 70 dominant trees. Both prevalence and severity were greatest on intermediate trees. Beech scale was present at all 34 plots. While scales were found on trees of all sizes, they were almost two times more prevalent and were more severe on mature trees than saplings. Neonectria cankers were detected at 34 plots. Neonectria was rare but most severe on dominant trees. Fewer than one third of saplings and one-sixth of mature trees were pest free.
U.S. disease assessment
BLD was present in 17 of the 30 plots. It was found on 75 saplings, 30 intermediate trees, and 38 dominant trees. Saplings and dominant trees had similar levels of disease; intermediate trees had significantly less. However, BLD severity was twice as high on saplings compared to mature trees. BLD was present on more than half of the seedlings assessed – 46 out of 82. Beech scale was present in 20 of the 30 plots. It was significantly less common and severe on saplings than on mature trees. Neonectria cankers were present in only 4 of 30 plots. Canker prevalence and severity did not differ significantly among size classes.
Distribution and Effects of Beech Scale and BBD
While beech scale attack facilitates invasion by the Neonectria fungi, the disease – BBD complex – had the most limited distribution of the three pests in this study. It was found on only ~4% of beech trees throughout the study area. The disease was first reported there in the early 2000s. Although no one knows why, it has spread more slowly there than in areas to the east (Reed et al. 2022).
As is the case with beech scale, BBD disproportionately affects large diameter trees. Typically, BBD kills more than half of mature beech within 10 years of its arrival. Dying trees produce prolific root sprouts resulting in dense beech sapling understories that impede regeneration of less shade-tolerant tree species. The persistence of thickets of disease-vulnerable small beech perpetuates the disease. BBD is the only forest disease in North America that can inadvertently intensify itself by increasing densities of its host while suppressing other species.
Beech Forest Community Change in Response to Combined Impacts of BBD and BLD
It is unclear how forests will change as beech die. Some expect saplings of species already present — red maple, white ash, and, especially sugar maple — to exploit the canopy gaps. Of course, white and green ash are under attack by the emerald ash borer; DMF their ability to reach the canopy will depend on the success of biocontrol agents.
However, if BBD or BLD resistant beech survive or if BLD fails to persist, future forests might instead consist of beech thickets that would prevent all but the most shade tolerant species from establishing. Heavy deer predation on maple seedlings and saplings might also play a role. A third possibility is that morbidity from BBD and BLD might lead to uneven-aged conditions that allow younger trees — perhaps even shade intolerant species e.g., oaks — to establish.
Invasive plants also have the potential to fill gaps left by declining beech. While maple-beech forests often have sparse understories due to low understory light levels, pest-caused canopy gaps are expected to increase the abundance of invaders, especially in small woodlots and forests near urban areas. Several shade-tolerant invasive shrubs are already present in low numbers: Japanese barberry (Berberis thunbergii), tatarian honeysuckle (Lonicera tatarica), multiflora rose (Rosa multiflora), and buckthorn (Frangula sp.). Reed et al. (2022) note that these species, plus privet and autumn olive, can take advantage of small canopy gaps, especially when soils are disturbed, e.g., by active intervention to counteract the loss of beech.
Precautionary Research and Management
Reed et al. (2022) call for enhanced monitoring of beech forests focused on
the timing of BLD presence relative to tree age and size – which might affect competitiveness of sprouting beech in the understory; and
compositional and structural change in forests with BLD or to which it is likely to spread
They also recommend abandoning the management approach for BBD currently recommended by foresters. It calls for removing scale-susceptible beech so that resistant genotypes increase in prevalence. In forests with both BBD and BLD, they conclude, management of natural regeneration is unlikely to succeed because BLD will kill sprouts and saplings that might be resistant to scale. They recommend instead active management of the forest to promote mast-producing, shade intolerant species, such as oaks and hickories.
They also recommend increased support for resistance-breeding programs. Such programs already target BBD, based on the estimated 1% of American beech that show some resistance. Now those programs need to incorporate BLD resistance. (Reed et al. note that small numbers of beech show few or no BLD symptoms so might possess resistance or tolerance.)
grafted beech for resistance breeding; photo by Rachel Kappler, then USFS (now Great Lakes Basin Initiative & Holden Arboretum)
Unfortunately, the Canadian beech breeding program’s future funding is highly uncertain. To counter this threat, in part, Reed et al. (2022) suggest cryopreserving beech embryos from Canada to develop a beech conservation collection that would be available for a more robust, future Canadian breeding program. The USFS is trying to develop methods to screen trees for resistance to BLD, specifically to the nematode (J. Koch, USFS, pers. comm.)
Another approach would actively manage beech stands in which potentially BLD-resistant beech grow to help these trees reach the canopy and reproduce. In the absence of management, any BLD-resistant beech seedlings might be overtopped by faster growing, shade-intolerant species – especially if the gaps promote soil drying or sun scald.
Finally, breeding programs need to factor in the beech leaf mining weevil, DMF which — as I noted in the beginning — is spreading across Nova Scotia and could spread to the rest of the native range of beech (Sweeney et al., 2020).
The Department of Agriculture has created a website on the Department’s plant-breeding efforts. It includes a subwebsite on USFS efforts. However, I did not find much useful information there.
SOURCES
Lovett, G.M., C.D. Canham, M.A. Arthur, K.C. Weathers, and R.D. Fitzhugh. 2006. Forest Ecosystem Responses to Exotic Pests and Pathogens in Eastern North America. BioScience Vol. 56 No. 5 May 2006)
Reed, S.F., D. Volk, D.K.H. Martin, C.E. Hausman, T. Macy, T. Tomon, S. Cousins. 2022. The distribution of beech leaf disease and the causal agents of beech bark disease (Cryptoccocus fagisuga, Neonectria faginata, N. ditissima) in forests surrounding Lake Erie and future implications Forest Ecology and Management 503 (2022) 119753
Sweeney J.D., Hughes, C., Zhang, H., Hillier, N.K., Morrison, A. and Johns R. (2020) Impact of the Invasive Beech Leaf-Mining Weevil, Orchestes fagi, on American Beech in Nova Scotia, Canada. Frontiers in Forests and Global Change | www.frontiersin.org 1 April 2020 | Volume 3 | Article 46
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
I often blog about the forest pest situation in the UK because its scientists provide lots of easily accessible information. This blog has new information on Britain and – I am pleased to add – on Ireland!
European ash trees alongside the Malham Cove path in Yorkshire; KA via geograph
UK Overview
British woodlands cover just 13% of total land area (just over one-third of the European average of 37%). Their value is increasingly recognized—especially their role in combating climate change through carbon sequestration, flood mitigation and urban cooling. Realization of these benefits is driving new policy to increase woodland cover. In 2019–2020, 13,700 ha of new woodland was created in the United Kingdom (Green et al. 2021). The U.K. government has pledged to plant 30,000 ha of broadleaf and coniferous woodland every year as part of its climate change mitigation strategy (Donald et al. 2021). One example, the ‘northern forest’ scheme, involves planting 50 million native trees over 25 years (Green et al. 2021).
Risks Associated with Conservation Plantings or Translocations
On-going conservation planting efforts plus these ambitious new plans prompted Donald et al. (2021) to assess risk that pathogens might be introduced into the environment as a result of putting native plants in natural habitats. The focus of their study is the planting of common juniper (Juniperus communis)in habitats throughout England, Scotland, and Wales.
Juniper killed by Phytophthora austrocedri; photo from British Forest Research
Juniper is one of three native conifers in the UK. It has been in decline for decades, which conservationists hope to reverse. Now, though, juniper populations are experiencing significant mortality from disease. In 2012, the causal agent was determined to be the non-native pathogen Phytophthora austrocedri. The presence of a single genotype in ~60 geographically separate locations across Scotland and England lends support to idea that the pathogen is being introduced to these sites through some human mechanism. Phytophthora austrocedri has not [yet] been detected in Northern Ireland.
British and European nurseries have contained many Phytophthora pathogens. Hence Donald et al. (2021) sought to determine whether the pathogen is being introduced through use of nursery stock in these well-intentioned plantings. (I have blogged about a similar problem in California restoration plantings.)
The authors found that 19% of P. austrocedri detections are within 2 km of a known planting. The more frequently junipers were planted at a site, and the more cuttings planted during each planting effort, the higher the likelihood that nearby junipers would be infested by P. austrocedri. They conclude that transplanting material is a significant risk pathway for the introduction of disease. The key factor appeared to be the origin of the material. A higher percentage of stock at sites with P. austrocedri outbreaks for which data were available had been raised in a central location by the organization doing the planting or obtained from commercial nurseries. No P. austrocedri was detected in Wales. There, unlike in Scotland or England, the majority of plants were sourced from a commercial nursery that only grew juniper collected from Welsh populations and did not trade with other retailers.
Planting juniper has risen rapidly since the mid-1990s. The highest percentage of planting events co-occurring with disease outbreaks were conducted in 2000–2009. It is likely that there is a time lag between planting and disease detectability. If so, the even larger planting effort since 2010 probably will produce many more P. austrocedri outbreaks that will become visible in the future. And that might not be the end. Planting guidelines have been revised based on pathogen detection. However, the entities doing the planting have not changed their approach, especially regarding site selection.
Donald et al. (2021) also found serious data gaps in these programs beyond the health of propagules. They found:
1) very incomplete knowledge of which organizations are doing the planting;
2) poor attention to traceability of source material; and
3) very little follow-up to check the success of planting projects.
The authors concluded that planting projects have had mixed success in restoring juniper populations. They called for changes in planting strategy to reduce the risks of pathogen introduction.
They also note that efforts to slow the spread of P. austrocedri – for which there is no treatment – are more expensive and less likely to succeed than measures aimed at ensuring that nurseries are free of Phytophthoras. California native plant nurseries have shown that nurseries can maintain Phytophthora-free stock.
Risk of Nursery-spread Pathogens & Willingness of UK Nurseries to Adopt BMPs
Great Britain has experienced an accelerating series of Phytophthora outbreaks and disease epidemics affecting British trees. Introductions detected just since early 2000s include P. ramorum, P. kernoviae, P. lateralis, P. austrocedri and P. pseudosyringae. In all the above cases, imported planting material either is confirmed or strongly implicated as the likely route of intro (Green et al. 2021).
To address this threat – and with massive planting projects proposed – in 2016 the British forest research entity initiated the multidisciplinary ”Phyto-threats” project. Its goal was to understand the drivers of rising Phytophthora infestations and opportunities for mitigating them. The project:
(i) examined Phytophthora distribution and diversity in different nursery management systems;
(ii) assessed the social and economic feasibility of a nursery accreditation programs to curb the risk; and
(iii) identified Phytophthora risks by modelling introduction, establishment and spread of species in relation to biological characteristics, environmental factors and trade flows.
The assessment of Phytophthora presence in nurseries involved collecting 3,624 water and root samples from 163 host genera growing in plant nurseries across the U.K. over a three-year period. Sampling was not random but targetted to facilities thought to harbor Phytophthora. About half of the samples tested positive. They identified 63 species of Phytophthora. Among the most commonly detected species are several that are considered pathogenic — P. cinnamomi, P. cryptogea/pseudocryptogea, P. syringae, P. cactorum, P. cambivora, P. plurivora and P. nicotianae. P. ramorum was found in 12 samples; P. lateralis and P. austrocedri were each found in 10 samples. Several Phytophthora species are potential new records for the U.K. (i.e., P. castanetorum, P. palmivora, P. pseudotsugae,P. tentaculata,P. terminalis, P. uliginosa).
They also saw evidence for Phytophthora root infections in newly arrived plants imported from the European Union.
Their finding raised question about whether Phytophthora can be transported in peat-free potting media, that is, coconut fiber or coir.
The widespread presence and the diversity of Phytophthora found in nurseries was linked to high-risk management practices. These included: careless disposal of culled plants, the near presence of trees along nursery boundaries, and, especially, open water sources. [These factors are essentially identical to infection-facilitating factors found by researchers in California, Oregon, and Washington State. See advisory issued by Oregon State University Extension.]
The project also assessed the feasibility of nursery accreditation programs. The authors consulted widely with nursery owners and customers and conducted a cost-benefit analysis. Regarding nursery practices, owners claimed they were already addressing issues related to water storage in enclosed tanks, clean/covered storage of growing media, installation of drains or free-draining gravel beds, raised benches, and tool disinfestation stations. Therefore the new analysis focused on seven other topics: water testing for pathogens; water treatment s; quarantine holding areas for imported plants; composting or incineration of culled plants; boot and vehicle washing stations; and purchase from only trusted or accredited UK suppliers.
The study found that nurseries would support an accreditation program. However, their support required that costs not be “prohibitive”, actions required not be “unreasonable”, the scheme provide a safety net; and that measures exist to deter non-compliance. Nursery staff wanted to see evidence of consumer demand – a willingness to drive farther to buy “clean” plants, or to pay higher prices for them. The cost-benefit analysis reached a worrying conclusion: nurseries would benefit financially from introducing best practices only when the program would prevent introduction of a wider range of pests and pathogens, not only Phytophthoras. Green et al. (2021) note that the overall net benefit to society from nurseries adopting best practices would be much more substantial. That is, healthy trees are important in meeting carbon sequestration goals. They did not explore whether society should subsidize nurseries’ participation in BMP accreditation programs.
Ireland and Northern Ireland
The island of Ireland (Ireland and Northern Ireland) is thought to have fewer plant pests than other European countries due to its island status and because of its national and international phytosanitary regulations. O’Hanlon et al. (2022) do not mention another possible factor: the likelihood that import volumes to Ireland were probably much lower until the recent vitalization of the Republic’s economy.
O’Hanlon et al. (2022) sought to establish baseline information so scientists can track changes as trade increases and the climate changes. Their search of the literature and unpublished sources identified 396 forest pests on the island, including 11 bacteria, 20 oomycetes, 150 fungi and 215 arthropods. They believe these figures are all probably underestimates. At least 44 of the pests or pathogens are probably non-native to Ireland. (Determining original ranges is difficult, especially for pathogens.)
The Republic of Ireland is one of the least forested countries in Europe. Forests cover ~ 11% of the land area. In Northern Ireland, it is even less: ~ 8%. These forests are predominantly plantations of exotic species. In the Republic, Picea sitchensis makes up 51% of the forest area, Pinus contorta another 10%. Other exotic species planted are Picea abies (4%) and Larix kaempferi. In Northern Ireland, ~ 62% of the forest area is composed of conifer mixtures. Planting of P. sitchensis has accelerated recently, probably as a result of removal of ash and larch because of their vulnerability to pests already established on the island.
Sitka spruce plantation in U.K. Adam Ward, Geograph.org.uk
O’Hanlon et al. (2022) note the great vulnerability of these monocultures to pests. They found 51 pests native to Ireland that are associated with non-indigenous tree genera. They are also concerned about pests introduced from other parts of Europe. For example, green spruce aphid (Elatobium abietinum, native to Central and Eastern Europe) is already attacking Sitka spruce. A second pest of spruce, Ips typographus, which is native to much of Europe but not the British/Irish isles, is not yet established on the island. Northern Ireland imports bark and wood from Europe for processing. Ips typographus has been associated with at least one such shipment.
Non-native forest pests and pathogens also threaten tree species native to Ireland. These include:
Dutch elm disease caused by fungi from the genus Ophiostoma vectored by bark beetles of the genus Scolytus. The second outbreak, caused by the more aggressive pathogen 0. novo-ulmi, was detected in Britain in 1965 and in Ireland in 1977. It caused considerable mortality of elms in Northern Ireland throughout 1970s.
Phytophthora ramorumwas recognized as a threat to forests in Europe only in 2010, when extensive mortality of Japanese larch was detected in Britain. The Republic of Ireland has only the EU1 lineage of the species. Northern Ireland has both the EU1 and EU2 lineages – the former only in nurseries.
Phytophthora disease of alder (caused by several Phytophthora species) was confirmed in Ireland in 2001. However, symptoms of the disease were noted as far back as 1995. It is likely that there are many other Phytophthora species present but not yet recorded.
Ash dieback disease (causal agent Hymenoscyphus fraxineus) on European ash (Fraxinus excelsior) has spread across Europe from Poland beginning in the 1990s. It was confirmed on the Irish island in 2012. Authorities made significant attempts to eradicate the disease, but were not successful. It is now recorded in every county in both Northern Ireland and Ireland. Damage to the economy, environment, and society are expected to be large. The Irish government had helped plant more than 13,000 ha of ash between 1992 and 2012. An estimated 2.9 million ash trees are in Northern Irish hedgerows. British scientists say more than 1,000 fauna species are associated with ash trees.
A second pest on ash — ash sawfly (Tomostethus nigritus) — was detected in Northern Ireland in 2016; it has defoliated hundreds of trees in Belfast.
In recent years, forest pest incursions have increased at a relatively steady rate, comparable to other countries, including Britain. In the 1970s, 26 species were reported; in the 1980s, 27; in the 1990s, 16; in the 2000s, 37; between 2010 and 2017, 28. See the graph in Fig. 2
There is a strong link between pest and pathogen findings in Britain and Ireland. O’Hanlon et al. (2021) list 16 insects and pathogens detected in Britain after 1960 which were later detected in Ireland. The list includes H. fraxineus, 0. novo-ulmi, Phytophthora ramorum, and Phytophthora lateralis. The average delay was 10 years. The authors note that the two islands share similar ecological conditions and hosts, are nearby, plus there is substantial travel and exchange of goods between them. For example, in 2018 an estimated 30,000 metric tonnes of conifer roundwood was sent from Scotland to Northern Ireland for processing.
There are very limited physical checks on plants or plant products moving between Ireland and Northern Ireland. The exception is conifer wood that is not bark-free. European Union regulations require that such shipments be accompanied by a plant passport that certifies that the wood has been inspected by a professional operator authorized by the NPPO of the exporting country. What rules will apply now, after BREXIT, remains unclear. Because of concerns about re-igniting sectarian conflict, most political figures want the border on the island to be almost invisible.
The Europhyt database for the period February 2006 – November 2016 documented interception of numerous high-risk pests at the British and Irish borders, including Anoplophora chinensis and A. glabripennis; I. typographus; Monochamus alternatus; H. fraxineus; and P. ramorum O’Hanlon et al. (2021). believe many more go undetected. O’Hanlon et al. (2021) report specifically on detections on commodities from China, especially on wood packaging. One detection on imported plants of interest to me is that of Discula destructiva(dogwood anthracnose). The article does not mention the origin of the shipment. The native British dogwood, Cornus sanguinea, would presumably be vulnerable to this Asian fungus, which has already caused widespread mortality of woodland dogwoods in North America.
Cornus sanguinea; photo by Hans Hillewaert
In addition to reviewing the current situation, O’Hanlon et al. (2021) note pertinent facts about current policy and future science. First, while the two political units on the island have a history of plant pathology expertise, there has recently been a reduction in the number of practicing forest pathologists, mycologists and entomologists. (I and others have complained about the same deterioration in expertise in the United States.)
Second, they describe the years of delay before official recognition that the pathogen Gremmeniella abietina was present in Northern Ireland. This delay resulted from officials refused to accept data from molecular detection tools.
O’Hanlon et al. (2021) add their voice to others criticizing the international phytosanitary system (they cite six major publications: Brasier 2008; Liebhold el. al. 2012; Santini et al. 2012; Eschen et al. 2015; Jung et al. 2016; Meurisse et al. 2019). The failures are (i) visual inspections can miss asymptomatic infections, (ii) limited resources mean only a small proportion of commodities can be inspected, (iii) allowing the use of fungicides masks disease symptoms on plants, (iv) list-based regulations don’t address undescribed organisms and (v) countries vary in how aggressively they carry out the required phytosanitary procedures. O’Hanlon et al. (2021) conclude that “Until these issues are addressed it is likely further increases in the numbers of non-native pests and pathogens of trees will increase.”
The authors note that Eschen et al. (2018) suggested that risk analysis should focus on the commodity (commodity risk assessment) rather than on an individual pest. I have made a similar suggestion, although less clearly worded.
Finally, O’Hanlon et al. (2021) note that climate change is expected to increase the island’s vulnerability to tree-killing pests and pathogens due to fewer frost days, more rain in winter, increased chance of drought in summer, increased average annual temperatures, and more frequent weather extremes. These changes are likely to affect the amount of damage caused by both native and introduced pests organisms. Range shifts in both pests and pathogens and their natural enemies; physiological or behavioral responses in the pests; phenological changes in the hosts; and increased stress on the trees will combine to affect damage.
SOURCES
Donald, F.; Purse, B.V.; Green, S. 2021. Investigating the Role of Restoration Plantings in Introducing Disease—A Case Study Using Phytophthora [UK] Forests 2021, 12, 764
Green, S., D.E.L. Cooke, M. Dunn, L. Barwell, B. Purse, D.S. Chapman, G. Valatin, A. Schlenzig, J. Barbrook, T. Pettitt, C. Price, A. Pérez-Sierra, D. Frederickson-Matika, L. Pritchard, P. Thorpe, P.J.A. Cock, E. Randall, B. Keillor and M. Marzano. 2021. PHYTO-THREATS: Addressing Threats to UK Forests and Woodlands from Phytophthora; Identifying Risks of Spread in Trade and Methods for Mitigation. Forests 2021, 12, 1617 https://doi.org/10.3390/f12121617ý
O’Hanlon, R., Ryan, C., Choiseul, J., Murchie, A.K. and Williams, C. D. 2021 Catalogue of P&P of trees on the island of Ireland. Biology and Enviro
Proceedings of the Royal Irish Academy 2021. Vol. 121, No. 1.12-45 DOI: 10.3318/ BIOE.2021.02
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
Scott Schlarbaum collecting butternuts; photo by F.T. Campbell
I have blogged several times about the need to enhance efforts to breed trees resistant to the most damaging of the hundreds of introduced insects and pathogens. Others concur – see reports by the National Academy of Sciences in 2018; several publications by USFS scientists Richard Sniezko and Jennifer Koch; a workshop hosted by Purdue w/ USFS support, the creation and efforts of several consortia – Whitebark Pine Ecosystem Foundation, Great Lakes Basin Forest Health Collaborative, Forest Restoration Alliance …
Also, Richard J. A. Buggs, of the Royal Botanic Gardens, Kew, recently summarized barriers to tree breeding. It was published as an especially thoughtful editorial in Plants People Planet in anticipation of the International Year of Plant Health in 2020 (see reference at the end of this blog). That issue included several related articles, also noted below.
R.J.A. Buggs’ Perspective on Tree Breeding
Buggs says the need for tree resistance research is greater than ever before. First, damage caused by introduced insects and pathogen is rising. Plus, we now recognize trees’ importance in capturing atmospheric carbon. He sees encouraging signs of growing public awareness of both factors. Also, he thinks citizen science might reduce the cost of some activities … although he doesn’t name which they are.
Dr. Buggs lists six major hindrances to breeding programs, including some aspects that I, at least, have not considered:
1) Trees’ size and long generation times mean research is necessarily slow. One result is it is hard to formulate research proposals that match funding cycles. This in turn means a dependence on long-term institutional commitment from well-funded organizations, and such institutions are rare.
I point out that the U.S. government – especially the USFS – is one such institution. Unfortunately, it has so far been reluctant to take commit major resources to breeding pest-resistant trees. Every year I urge you to lobby Congress on appropriations for the agency. In this context, do you understand that while the USFS Research budget receives approximately $300 million each year, less than $5 million of that total is allocated to researching invasive species (of all taxa)? Some gaps are filled by projects funded by the Forest Health Program. You will have a new opportunity to lobby Congress for Fiscal Year 2023 in the spring!
2) On the other hand, reliance on long-term institutional funding shelters projects from multidisciplinary peer-review that could introduce improved technology or methods. This lack of peer review also contributes to a perception among other scientists that tree resistance research is a scientific backwater.
3) Similarly, studies requiring a long time horizon don’t fit publication schedules. Again, the result is that the findings often appear only in institutional reports or conference proceedings. This means they are hard to find and often lack external peer review at not only the proposal stage but also before publication.
4) The long decades without clear success in dealing with Dutch elm disease (but see recent encouraging developments here) and chestnut blight (see The American Chestnut Foundation here) gave the impression that resistance breeding of forest trees is impossible. Buggs says pest resistance problems are easier to tackle for other trees.
TACF American chestnut; photo by F.T. Campbell
5) Those considering what efforts to fund might demand complete resistance to the pest. This goal is not only unrealistic – it is often unnecessary. Often lower levels of resistance or tolerance can result in trees that can be self-sustaining. Dr. Sneizko concurs; see his article appearing in this issue.
6) Forest stakeholders differ over the goal of developing resistant trees. Some think any human intervention is unwarranted in wilderness areas. Some want a tree as similar as possible to pre-epidemic trees. Others want a tree that produces more timber.
Other Significant Articles
A second article in the same issue of Plants People Planet (Federman and Zankowski) discusses the USDA’s commitment to new approaches in tree resistance research.
I found a third article that discusses British approaches to mitigating tree pests to be more informative than Federman and Zankowski – although somewhat worrying. Spence, Hill and Morris praise the U.K.’s Plant Health Risk Register, which they say has enhanced vigilance on possible new pest introductions. However, the authors describe resistance breeding as a strategy to be considered “when a pest has established such that a tree population is unable to recover, and where a genetic basis for resistance is demonstrable in a proportion of the tree population.” Dr. Sneizko, and others – and I! – call for initiating exploration of the potential for resistance breeding much earlier in an invasion.
A fourth article – by Richard Sniezko and colleagues — describes encouraging levels of partial resistance to white pine blister rust in two western white pines and evidence for both qualitative and quantitative resistance to Phytophtohora lateralis in Port-Orford Cedar.
Port-Orford test seedlings; photo courtesy of Richard Sniezko
A fifth – by Showalter et al. — reports encouraging levels of resistance to both emerald ash borer DMF and ash dieback in European ash. The authors conclude that a breeding program might be a viable solution to both pests.
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
A group of scientists has published a report on Canada’s invasive species programs (see reference at the end of this blog). It compares the structures and procedures of Canada’s federal government to those in the U.S., Australia, and New Zealand.
The report focuses on proactive measures aimed at preventing introductions, including cross-border introductions from the U.S. It does not describe efforts to prevent spread between provinces. Nor does it address efforts by provincial or territorial governments, Tribes, or non-governmental organizations (NGOs).
The authors seek to understand how federal infrastructure, strategies, and decisions have contributed to outcomes. Their principal recommendation is that Canada should accord protecting biodiversity as much importance as preventing direct economic impacts from invasive species – unlike now and in the past. Those economic impacts are substantial, estimated at $34.5 billion (Canadian) each year.
The authors think that such a focus is appropriate because Canadians depend on the stability and function of a wide range of ecosystems and express strong interest in protecting their environment. Canada has also accepted obligations to protect biological diversity by joining the Convention on Biological Diversity (CBD). One of those obligations was that, by 2020, the country would have put in place plans targetting high risk species and pathways of introduction..
The report notes that Canada faces some unique challenges: three coastlines, the intimate relationship with the U.S. (i.e., a long border and diverse shared water bodies), vast area, and very low human population density. The last might result in fewer incidents of human-mediated dispersal. However, it is likely to present logistical challenges in detecting and managing any invaders. In addition, common, popular Canadian recreational activities — camping, boating, and fishing — can contribute to invasive species’ introduction and spread.
hemlock mortality due to hemlock wooly adelgid in Nova Scotia; HWA had spread from the U.S. Photo courtesy of Celia Boone, NS Department of Land and Resources
Canada’s Biosecurity Efforts
Canada adopted its Invasive Alien Species Strategy in 2002. The plan addresses four stages of invasion: 1) prevention of new introductions; 2) early detection of newly introduced species; 3) rapid response to new invaders; and 4) management of species that are established and spreading.
The report laments that Canada lacks centralized oversight of it biosecurity efforts in preventing new introductions across all pathways. That is, responsibilities are divided among several agencies, depending on the associated commodity or resource. One result is that similar pathways are regulated differently. One example is ship-mediated vectors. Ballast water is strictly regulated by both Canadian regulations and the 2004 Convention for Control and Management of Ship’s Ballast Water and Sediments (which took effect in 2017). However, commercial fishing and recreational boats are not federally regulated.
In accordance with the CBD, the Canadian government submitted a report in 2018, claiming to be on track to achieve its 2020 targets. The government had identified priority pathways: shipping, horticulture, aquarium/pet trade, transport containers, road construction, and recreation (e.g., boating). Several had been regulated at least partially, including wood packaging, forestry products, and plant products. Legislative and regulatory tools had been strengthened, including risk assessments and management plans for ballast water, recreational boating, and wood packaging. (I cannot explain the conflicting assessments of the regulation of recreational boating.) Also, national plans had been developed for several priority species, including the Asian subspecies of Lymantriadispar and emerald ash borer. The country acknowledged gaps with regard to emerging animal diseases, the pet trade, and dispersal across the U.S. border.
Comparing Canada to Other Countries (see Table 2)
The United States: I am disappointed by the report’s comparison of Canadian and U.S. invasive species programs because it considers formal structures rather than how the programs work in reality. The Canadian report allots much greater authority to the U.S.’ interagency National Invasive Species Council (NISC) than I think it actually enjoys.
The report notes the abundance of U.S. data on invasive species’ distribution and hosts. It cites specifically the USDA Forest Service Forest Inventory Analysis. It also notes the importance of several transborder non-governmental organizations, including North American Invasive Species Management Association (NAISMA) and EDDmaps and binational entities such as the Great Lakes Fishery Commission.
Australia: The Canadian report praises the existence of an Inspector-General of Biosecurity who conducts independent reviews of biosecurity issues. It also applauds the coordinating role of the Intergovernmental Agreement on Biosecurity, which sets roles, responsibilities and governance agreements for biosecurity responses at all levels of government. Finally, it notes that the Department of Agriculture, Water and Environment (DAWE) created a National Priority List of Environmental Pests, Weeds and Diseases.
I have no independent understanding of how successful Australia has been in addressing invasive species. However, several forest health experts appear to have been dissatisfied with the country’s response to the introduction of Eucalyptus rust; see my blog.
New Zealand: Again, the report praises centralization of policy and government efforts in the Ministry for Primary Industries (MPI) under the provisions of the Biosecurity Act of 1993. The MPI advises the Minster for Biosecurity – which has no counterpart in the government of Canada. The report also notes that while New Zealand expects landowners and individuals to manage their own biosecurity risks, they can claim compensation if they suffer loss due to a biosecurity action, e.g., destruction of nursery stock. The Canadians think this provision might encourage people to report invasive species. New Zealanders are trying to create an all-citizen “team” to address invasive species. One way they promote this idea is to issue awards recognizing individuals’ efforts.
I wish the Canadian report had also looked at South Africa, which has done such a good job in its invasive species reports.
Four Case Studies
The report includes four case studies: a “historical failure”, a “historical success”, and two substantial current threats.
Preventing introductions of zebra and quagga mussels is described as a “historical failure”. There was no relevant preventive measure in place at the time they were introduced. Since preventive measures were made compulsory, no invasive species have been documented as becoming established in the Great Lakes via the ballast water pathway. Such introductions have occurred in less well-regulated marine systems.
Eradication of the Asian longhorned beetle (ALB) is described as a “historical success”. The initial Toronto outbreak was not completely eradicated; a small residual population was detected about a decade later and eradicated then. The report notes that the Toronto outbreaks were noticed by citizens rather than the relevant government agency. So “success” is attributable to chance and astute citizens rather than rigorous enforcement. I note that most U.S. detections of wood borer infestations are also detected by citizens. It is probably unrealistic to expect all detections to result from official programs.
The threat to Canada from the spotted lanternfly (SLF) is high since it could cross the land border from the U.S. Its principal host, Ailanthus, is widespread in southern Canada – not just in the East but also in Saskatchewan and Alberta. The insect’s egg masses are easily transported on a wide variety of vehicles. The report does not enumerate how many trucks or trains cross the border each year. The report laments that Canada has not adopted a clear monitoring plan aimed at detecting early SLF introduction.
Finally, four species of carp native to Asia threaten to invade the Great Lakes, for example through the Chicago canal or Sandusky River. Canada has asked citizens to be on the alert, and is exploring use of eDNA monitoring systems.
Lessons and Recommendations
The report highlights lessons learned in its four-country review and makes a series of recommendations:
1) Value biodiversity as well as economic and industrial interests.
The Canadian Species at Risk Act (its endangered species legislation) does not mention invasive species as a cause of endangerment. The Natural Sciences and Engineering Research Council now provides a centralized repository of biodiversity monitoring data which will help overcome data limitations associated with invasive species surveillance and risk modelling.
2) Consolidate regulatory frameworks
Canada should follow Australia and New Zealand in assigning a single body to be responsible for biosecurity. It should set biosecurity priorities, coordinate research and management at various government levels, and lay the groundwork for consistent actions.
3) Strengthen partnerships with the public and Indigenous communities
The report’s authors praise New Zealand’s efforts to engage all citizens in biosecurity. Canada would benefit from enhanced educational efforts – which are stronger now thanks to the growing availability of phone apps. Canada should ensure that Indigenous communities’ perspectives and knowledge are integrated into the program.
4) Strengthen partnerships with other countries
Canada should prioritize discussion of biosecurity with its trading partners, particularly in developing multinational trade agreements. This is a key improvement that the U.S. could make, too.) It is particularly important to strengthen collaboration with the U.S.
4) Adapt to future conditions
Canada will need to anticipate changes due to population increase and climate change. Research needs to recognize and overcome current taxonomic and geographic biases. Also, research should focus on developing new technologies and treatment techniques proactively, before they are needed. One area of concern will be migration corridors (or “assisted migration”) undertaken to protect biodiversity as the climate changes.
5) Anticipate conflict
The government must expect different perspectives among stakeholders. Greater transparency in education campaigns might help prevent disagreements from becoming serious barriers to action.
SOURCE
Reid CH, Hudgins EJ, Guay JD, Patterson S, Medd AM, Cooke SJ, and Bennett JR. 2021. The state of Canada’s biosecurity efforts to protect BD from species invasions. FACETS 6: 1922– 1954. doi:10.1139/facets-2021-0012 Published by: Canadian Science Publishing
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
